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Understanding Your Four-Stroke Engine: Event Timing
Timing, they say, is everything, and that’s particularly true with engines.  Understanding how and when the individual events happen, and why they happen when they do will help you understand why they have to be set up as they are, and that always makes it easier to figure out what’s going on when problems arise. Let’s start by going over the basic way the engine works, and what events need to occur and when.  First, we’ll look at the simple basics, then at the reason things happen exactly when they do.  To simplify the discussion, and to make it more closely relevant to dirt bikes, we are only going to discuss single cylinder engines during this explanation.  The term, “four-stroke cycle” means that the engine needs to move the piston up or down the bore 4 times to complete all the functions that go into producing power from gasoline.  Because the piston is connected to the crank via the connecting rod, each “stroke” takes a half revolution of the crank, or two full revolutions for the four necessary strokes.  The Four-Stroke Cycle A lot of folks have seen this simplified version, but let's review. The cycle starts with the Intake Stroke, near top dead center (TDC), where the piston is at its highest possible position, with the intake valve opening and the piston moving down the bore toward bottom dead center (BDC).  This creates a void above the piston that is filled by air from outside rushing in through the intake port to fill it, and that air carries with it the fuel added by either the carburetor or a fuel injection system. The rotating crank then begins to move the piston up the bore and the intake valve closes, trapping the fuel and air in the cylinder.  As the piston continues upward, the air/fuel mix is compressed, which heats it and increases the amount of force with which it will expand when ignited.  This is the compression stroke.  The power stroke begins near the top of that second stroke, when ignition takes place, starting the fire.  The crank rotates past TDC as the burning fuel begins to expand, and the combustion force pushes the piston down the bore, creating the rotating force on the crank that drives the whole works.   As the piston nears BDC again, the exhaust valve opens, and the piston is run up the bore to pump the spent gasses out through the exhaust port to complete the cycle with the exhaust stroke.  Half Speed Notice something here: The engine’s crankshaft rotated twice to produce four trips up and down the cylinder for the piston, but each valve only opened and closed once during that time.  To make this work, the camshafts have to turn at one half the engine speed, so the chain and sprockets, or gears, or toothed belt and sprockets used to drive them are set up at a 2:1 ratio.  Ignition also has to happen right on time, so each ignition system, whether simple ‘50’s style points, or the most sophisticated electronic, has to have something to signal when that is. Traditionally, this signaling trigger has been attached to the camshaft so that the spark occurred only once every other revolution, but engineers seeking to simplify the design of single cylinder dirt bikes found no reason that there could not be a spark on every revolution, so the trigger sensor was mounted at the crankshaft instead.  That means there is a spark on every revolution, instead of only once per each two-revolution cycle of the engine. The second spark happens at the end of the exhaust stroke, so there’s nothing present in the cylinder that would burn.  It also makes setting up the timing during assembly somewhat simpler by eliminating what used to be a common mechanic’s mistake of picking the wrong top dead center position. Getting Ahead of Things (The Engine is Dynamic) Simplified explanations of the cycle like the one we started with here always show the valves opening and closing right at TDC and BDC, but if you watch the piston position as you turn an engine over by hand to watch the valve gear operate, you will notice that the valves don’t open and close at the exact top and bottom of their respective strokes. That’s because the engine is a dynamic system, which means it’s something that moves, and it does so at a pretty high speed. Most MX 450’s make peak power at around 9000 RPM,  which means they make two full revolutions and complete an operating cycle in about 13 milliseconds at that speed.  The crank spins continuously, but the intake, exhaust, and combustion all stop and start again while that’s going on.  That means that all of these events actually have only a certain amount of time in which to occur, so they have to be started in advance so that they happen on time.  Again, we’ll look at the intake stroke first.  With the crankshaft spinning along at a few thousand revolutions per minute, if we were to wait until top dead center to open the intake valve, the piston will travel well down in the bore by the time the valve is open wide enough to let much air into the cylinder, so the intake valve begins to open around 20 degrees or more before top dead center (BTDC).  This does a couple of things.  For one, the exhaust stroke is just ending, and the inertia of the spent gasses leaving the cylinder creates a bit of a vacuum that helps get the intake air moving in.  There’s a little bit of built up pressure right behind the intake valve as a result of the intake valve having been slammed shut on a moving column of air at the end of the previous intake stroke, and that helps, too.  But mainly, we want the intake valve to have time to be open nice and wide as the piston moves through the fastest part of its down stroke so we can get the cylinder as full as possible.  On top of that, we’re going to keep the intake valve open until well after bottom dead center (ABDC) to take advantage of the inertia of the incoming air. Which brings us to the compression stroke.  The piston is now rising and pushing against the load of incoming air, stalling the flow into the cylinder, so the intake valve closes as this balance is struck, about 130 degrees BTDC.  With both valves now closed, the piston compresses the air and fuel mix to less than 1/10th its original volume to heat it up and to increase the force with which it expands as it burns.  This compression will continue until TDC, but the ignition has to happen well before that in order to extract the maximum power from the burning of fuel. The Power stroke, then, is initiated before the piston actually starts down.  This “spark advance” allows the burning gasoline time to start at one small point near the spark plug and spread across the combustion chamber to the point where it becomes confined by the piston and must push it down out of the way.  That’s where the power comes from.  If the spark occurs too late (is “retarded”), the piston will outrun the fuel burn and not much pressure will be applied.  On the other hand, if it happens too early (“advanced”) then too much pressure will be created while the piston can’t get out of the way fast enough, which leads to damage from detonation and the like.  The faster the engine turns, the more advance the ignition needs to keep up, so modern systems advance the timing as the RPM increases. At about 120-130 degrees ATDC, the energy from the fuel burn is so low that it really isn’t putting a lot of force on the piston any more, and the leverage that the piston has on the crank is getting pretty low, so the exhaust valve starts open before reaching BDC.  The pressure that remains from the burn starts the gasses flowing outward, boosted by the piston as it rises and pumps the bore clear.  The exhaust valve remains open past TDC to utilize gas inertia and help restart the intake airflow for the next cycle.  Am I 180 Out? People ask this a lot when they have trouble getting an engine running after they’ve set the cam timing up, or when they bring the piston up to Top Dead Center and find both valves open.  This is the common mistake we mentioned earlier, and it's one of the things that's more easily understood when you have a good grasp of the complete cycle.  It’s more of a car thing, but if you have an old classic four-stroke from the ‘70’s or before that uses cam driven breaker points, it’s sometimes possible.  These days, the answer is usually, “no.”  The old way of connecting the ignition to the engine mechanically, that of using a distributor or some other device driven at half speed by the cam, allows a mistake in assembly to be made.  A mechanic could position the engine at TDC, and if not careful to check, he could position the ignition trigger to fire during the exhaust stroke instead of the compression stroke.  This was referred to as being “180 degrees out” because the distributor or point plate was 180 degrees away from the correct position on the camshaft because of this. Actually, going by the crank, the ignition timing was 360 degrees out. But with the ignition trigger located on the crankshaft instead, as is the case with virtually all modern single cylinder dirt bike 4 strokes, that’s not possible.  Without the cams connected to the crank, one TDC is exactly like another; the rod’s at the top, and the spark signal is given as the crank gets there, every time.  So, the only thing that determines which stroke is which is the camshaft(s), and how they are positioned by the assembler.  That’s why the service manuals for such engines make no mention of checking for which of the two different TDC’s is used.  In operation, there is a second, "wasted" spark that happens near the end of the exhaust stroke.  What About Automatic Decompression? This is another area where really understanding the four-stroke cycle helps clear things up.  It's extremely common to hear people tell someone with a modern four-stroke single to "find TDC" before starting, but that's wrong.  When you turn the engine over slowly, you find it rotates fairly easily until you come to a "hard spot".  Without auto decompression, the hard spot is the point at which the intake valve closes to begin the compression stroke.  That looks like the picture below, "Non AD".              From this point, you would need to force the engine to compress about 80% of it's full stroke length worth of air, and that can be nearly impossible with the high compression ratios used these days.  What automatic decompression does is use a speed sensitive mechanical system to lift the exhaust valve off its seat at very low speeds (slower than the engine will idle at) until the engine gets a lot closer to TDC, but not past it, so that when kicked over from this position (or spun through it by a starter motor) there will still be enough compression to start, and both valves will be closed as the spark happens and the end passes top dead center.  That looks like the "Auto Decomp" picture above.  You can see that there will be a lot less effort needed to compress the air/fuel charge from here than from the normal, non auto decompression setup.  This, by the way, is where you want to be if you have an older manual decompression engine.  If you go past TDC instead of stopping just prior to it, you would have to kick the engine through nearly two full revolutions to get back to the compression stroke again, and it would still be at full strength. Once you have the whole picture set in your mind, you'll make fewer assembly mistakes, and you'll be able to catch on to problems more quickly.  A crusty old  mechanic told me a long time ago, "The best way to figure out why something works wrong is to know how it's works when it works right".  
Posted by grayracer513 on Apr 27, 2017

Alpinestars Corozal Adventure Drystar Boot
The Alpinestars Corozal Adventure Drystar Boot was designed for adventure and light to moderate duty dual sport riders who want a good quality boot, but are willing to give up some features for a more affordable price. I’ve ridden in a few other boots in this segment and at its sub $300 USD price, I think that the Corozal has put a few brands on notice. In contrast to Alpinestars MX boots, the Corozal is pretty toned down in terms of colors. It comes in all black, but I chose the oiled brown suede leather with black TPU shift pad & shin plate. It has an old school look that appeals to me and apparently others when I shared a pic on Instaglam. One design feature that stands out is that the Corozal only has two buckles. But, after many miles of use, both with & without in-the-boot knee protection, I can’t say that I noticed any downsides vs. boots with as many as 2x the buckles. They most certainly go on & come off quickly. In conjunction with an upper shin plate enclosure has a pretty generous patch of strong Velcro, the boots feel secure on your feet. Since we’re talking about buckles, the Corozal doesn’t get the aluminum units found on their upper-tier Toucan Gore-Tex Boot, but they function well nonetheless. Adjustment is the typical serrated back push in/pull out buckle straps with an arrowhead tip that easily threads through the buckle latch, closing securely with a "snap". When closed, the instep buckle does stick out a bit. There is a molded TPU ramp to deflect latch snags, but the buckle strap has an outward arc to it. While I didn’t manage to get trail brush jammed under it, it’s entirely possible. When I first slid the boots on, I thought that they were going to be too tight. They go on snugly. In hindsight, I felt this way because my current ADV/dual sport boots are on the loosie-goosie side by comparison. The Corozal are more form fitting and no matter how many hours I had them on, they were comfy. My rule of thumb is that if I notice something while I’m riding, it’s probably not that comfy and these boots were very much put on and forget about em’. Lastly, no break-in was required; they felt good right out of the box. Sizing appears to be true, the max circumference of the opening is 18”, and each boot weighs in at slightly over 3lbs.. The Corozal features a molded vulcanized sole that offers good foot peg traction and support in rougher conditions, but unfortunately the instep section is not replaceable for wear. Alpinestars did a good job balancing sole rigidity with walkability. Buyers in this segment do some walking when exploring and you can do so in the Corozal without looking like a robot. Not sure I'd do a 5 mile hike in them, but I have a bike. Why would I want to!? Also aiding walkability and operation of foot controls is what Alpinestars calls “Bio-mechanical lateral “flexi-blade” system”. More simply, it’s a semi-hinged system that allows for fore & aft movement at the ankle while maintaining proper support and protection. I had no issue with movements necessary for accurate shifts or rear brake modulation, but after a few rides, the hinge developed a squeak when walking. On Instaglam, others reported the same issue and when I mentioned this to the Alpinestars folks, they suggested a couple squirts of Silicone spray. This worked like a charm. In terms of protection, above I stated that I thought the boot was good for up to moderate dual sport use. Surely there are more protective off-road boots in the Alpinestars line-up and in the market in general, but for the audience the boot was designed for, I think the Corozal has the key areas covered. The toe box is hardened, steel shank, reinforced ankle, and TPU shin plate. The only area that I’d like see more protection built into is at the back of the calf. It does have foam padding that will absorb some hits, but I’d like to see some strategically placed TPU here. But I have to remind myself, sub $300 price tag… going to have to give on something. Lastly, Alpinestars doesn't specifically lists the Corozal’s Drystar membrane layer as waterproof, but “proven performance in difficult weather conditions.” Unfortunately, since I started riding with them in December, central FL has had very little rain. Probably the driest winter I recall. So, none of the riding conditions really tested this. However, I hosed them down pretty good with a garden hose for a couple of minutes and didn't notice any water intrusion. So, at the very least, I’d call them highly water resistant. I’ll need a wet FL summer to test waterproofness. I’ll report back. Overall, I like the Alpinestars Corozal Drystar Boot. They appear to be well made, comfortable, don’t hinder use of foot controls or walking, and offers a good level of protection for the ADV and mild to moderate dual sport riders they are targeting. Top the package off with a sub $300 price tag and they are serious competition for the segment. But, don’t take my word for it… No substitute for putting a pair on your feet for a bit at your local Alpinestars dealer.
Posted by Bryan Bosch on Apr 26, 2017

John Gallagher: "Bottom line it ends with me!"
With controversy surrounding Supercross this season associated with inconsistent penalties, I decided rather than criticize FIM Race Director John Gallagher I would sit down with him to understand what his job fully entailed.  After talking with John, I left with the impression that he is both knowledgeable about Supercross and truly cares about his position, the riders, and the crowd.  I also left with more questions about the overall rule structure of Supercross, specifically how loose the rule book is, ultimately allowing for human interpretation.  This is part 1 of my look behind the curtains of Supercross and who makes the important decisions.  This is all about John Gallagher, his responsibilities, decisions and his thought process. Who is John Gallagher and how did he get started in Supercross?  His involvement in Supercross began in 1976 as a flagger, from there he continued officiating and racing locally until he graduated from Riverside City College with Associates of Science in Motorcycle Technology.  Throughout his journey, John has been an official in Supercross, MTEG Ultracross, 4-Stroke Nationals, Thunder Bikes, Arenacross, Dirt Track, X-Games, and Endurocross from 1976 until present day.   When preparing for a race, John will fly into the race city the Thursday before racing weekend and spend his Friday and Saturday at the track.   His job consists of three different facets.   First is safety, John relies on his years of experience to determine the safety standards.  He does this by making sure there are no immediate dangers to the racers, officials, and crowd.  As it pertains to the crowd; making sure rocks, dirt chunks or motorcycles cannot make contact or do harm to any race fan.  A particular area of concern is behind the starting gate, ensuring bikes cannot toss roost into the stands.  The second facet is enforcing the rule book and confirming tech inspection is completed correctly.  The third facet is ensuring the program runs with-in the time allotted.  This includes allowing time for teams to complete bike changes or repairs while staying within the three hour television window.  John also is involved with the input to the promoter to determine the rider breaks and the length in time to give the riders in between heats.  He speaks with the teams and mechanics and considers their input when determining the schedule.  John also has twelve officials placed around the track to act as his eyes during the event.  John trusts each official’s interpretation as if he saw the incident himself.   While he trusts in what his officials’ witness, ultimately, it is John’s decision if a punishment is distributed. I asked John why he did an interview with Jenny Taft before informing Jason Anderson that he had been disqualified from Anaheim 2.  John stated he informed Jason's team manager and was adamant that the responsibility then fell to the team manager to deliver the news as he needed to get back to his duties.  John insisted if Anderson was not informed it was not his or any of the twelve officials’ responsibilities to seek Anderson out.  Once Anderson’s team manager was notified John got back to his nightly duties.  While Jenny Taft didn't have any issues finding Anderson, he was not in the mood to talk.  John told Jenny Taft immediately following the incident, “If it becomes physical on the track or off the track it results in an immediate disqualification.”   In comparison I asked John why Broc Tickle was not disqualified from Toronto after smacking Barcia in the back of the helmet, as that appeared to be “physical” off the track.  John replied, “Every guy knows there is the ability to make somebody swing on you, I could probably provoke you to be very angry with me.”  I also asked John why Tickle didn't receive the same punishment as Anderson at Anaheim 2.  John stated, “Mr. Friese was not doing anything to provoke any part of that [Anderson incident], not anywhere in it.”   In regards to his previous statement to Jenny Taft, I asked if Tickle had taken matters into his own hands by striking Barcia in the back of the helmet and if he should have been disqualified.  John responded, “And running into someone with their motorcycle is not considered the same thing?, which is what Justin did in reverse, those guys got close to each other and had a discussion but it was nothing like what Anderson did to Vince Friese, you cannot compare the two.  No possible way.”    John viewed the Anderson incident as one sided, while viewing the Tickle and Barcia incident as a couple of racers working out their issues. Therefore the latter punishment issued did not warrant severity.  I asked John, if Barcia ran his bike into Tickle after the race and Tickle smacked Barcia’s helmet, wouldn't he sit them both down for the night?  John said, “Not necessary to sit either guy down.  They had a disagreement, it got heated and I dealt with it.  Anderson’s incident was not this, it was all one sided. He was dealing with this issue because of what he thought happened on the track, and by the way, he [Anderson] was incorrect.  What happened on the track was not Friese’s fault.”  I asked John if Barcia was on probation and he confirmed, “No.  He was warned but not to that degree.”  He also stated when the Barcia and Tickle incident got out of hand he had to interject himself, but he preferred to let them work it out first.  Both teams got involved and asked for action, so he had no choice to intervene and punish both riders.  Tickle’s punishment included starting last in the Semi, receiving a written warning, and paying a fine.  Barcia received a written warning.   As far as the Chad Reed/Blue flag penalty, John informed me he contacted Reed on the Monday after the event informing him of his penalty.  At this time he tried every possible way to inform Reed of the appropriate way to appeal the penalty in a proper and timely fashion.  John attempted to inform Reed of the proper procedure, due to Reed’s past incident with the Black Flag and Trey Canard.  Once the black flag has been thrown, Reed had no way to appeal the penalty.  John confirmed this was not the reason he did not Black Flag Reed.  His concern was related to making sure Dungey didn't have another issue that might be slowing him down, such as a tire going down or a clutch slipping.  If Dungey was experiencing any issues, and Reed wasn't holding him up, then it would be unfair to Black Flag Reed.  Upon finding out Dungey had no issues, and to also have time to analyze all facets of the incident, is when John decided to penalize Reed.   As far as inconsistent punishments, John stated, “my job is to change behavior.  If a rider feels a certain behavior is acceptable and the rest of the paddock doesn't feel it is acceptable, I have to figure out how to take a group of people that are vastly different in ability, quality of team, and funding, to find a way to make this all work.”  In relation to different punishments for different riders John stated, “in regard to Jason Anderson, points are a big deal.  A fine not so much.  If you flip the situation and Friese threw the punches, a fine that would affect Anderson would bankrupt a Vince Friese and Vince doesn't have enough points for what Jason lost at that race now.  Vince would still owe me points.”   John determines decisions based on what is “equitable to each rider,” and the rule book allows this. Bottom line is punishments are his decision.  I asked if John considered punishing Barcia in St. Louis for his take out of Alex Ray (which he didn't see until watching the event on television Monday or Tuesday) and he said he told Barcia, “Justin learned that type of thing not only screwed the other guy but also took him out as well.”  He continued, “Is that the way you want to move forward because you are riding in the back right now?”  John admits there is no clear way to determine when an action requires punishment or it would be written in the rule book.  He determines punishments on a rider’s intent and whether or not riders can sort it out themselves.  His tasks do not physically allow him to interject himself in every issue.  In regard to punishments, John said, “Bottom line is it ends with me!" In Part 2 I will dive into the rule book and show how loopholes could be closed and ensure less human interjection.  This will draw clearer lines as to what is a penalty and what punishments should apply.  
Posted by Chris Cooksey on Apr 25, 2017

Oil for dummies: Bel-Ray answered my simple questions.
Oil for the common man: With all the talk about ratings and magical additives included in oil these days, I wanted to get with the guys at Bel-Ray (Andrew Hodges and Chris “Dang” McAvoy) to see how they could simplify things.  Changing oil is a necessary evil, and not a task I personally enjoy.  Working at Western Power Sports I sell many different brands of oil and have experienced the oil manufacturers tell me they have an unbeatable formula only to have an oil competitor explain the previous company was lying and they have the scientific data to prove otherwise.  Now, if you talk to motor builders they all have their favorite brand and a story as to why, maybe a bike that ran with no coolant or their impeccable reliability record.  What does all this mean?  Do formulas matter if I change my oil regularly? -    Yes! Regardless of whether you are changing your oil after 100 miles or 10,000 miles, you still want to have a good quality oil in your bike. Changing it after relatively short intervals does give you the option of running mineral oils without fear of oil degradation being a problem, but even then, it is still advisable to use a high quality product. Friction is there from the first revolution to the last, so an oil that provides excellent wear protection is a good idea no matter how often it is changed. Why do I need motorcycle specific oil, car oil is cheaper and I change it every ride?   -    This is a common preference I see and I definitely get the thinking behind it, but there are some aspects that I don’t believe riders doing this are fully considering.  Let’s assume you manage to find a high quality automotive engine oil that does not contain friction modifiers (which are deal breakers for a wet clutch) but still provides good gear and clutch protection (assuming this is for a bike with a shared sump).  1.    I agree with your comment in your introduction that changing oil is a chore so having to change it every single time I ride sounds like a nightmare. 2.    The cost of buying oil and a filter every single ride does not sound inexpensive no matter how cheap the oil is, so I doubt there is really much money being saved compared to a motorcycle specific product that can be changed much less frequently. 3.    Inexpensive automotive oils typically meet the absolute minimum standards for automotive use, so even a “high performance” car oil’s additive package is likely a bit underwhelming compared to a fully formulated motorcycle oil. 4.    Automobiles exert much less physical shearing on their oil compared to most motorcycles because their engines and transmissions are separate. Therefore, most automotive engine oils do not perform in shear resistance tests as well as motorcycle specific oils should. Viscosity loss due to shear can be a very bad thing for engine life so the product chosen should be verified for shear resistance in gearboxes. Does my motorcycle specific oil brand matter if I change it every ride? -    If the choice is between two brands that perform equally, then no the choice won’t matter. However, if one brand has better performance then the other, the choice should be clear.  Brand choice does matter, but there are many good brands to choose from. I have an obvious bias for Bel-Ray products, but my personal belief, because of the testing we do here, is that Bel-Ray products are the best in the market. Our approach to formulating and testing has provided us with decades of success and excellence. The methods we use to evaluate and develop our products have given us some of the best performing products we can find on the market today. So if you are trying to choose a brand, I am more than happy to shamelessly recommend Bel-Ray to you. What oil is best for bikes without separate gear oil?  Will a full synthetic make my clutch slip? -    The best oil to use in a bike with a shared sump for the engine and the transmission is a JASO rated engine oil. All JASO rated engine oils have to meet the minimum API standards for their respective performance levels so engine performance is guaranteed. However, the JASO regulations include additional performance requirements including clutch performance. There are four levels of performance in the JASO regulation, but only three of them are for combined sumps with a wet clutch: MA, MA1 and MA2. The only difference between MA, MA1, and MA2 is with regards to their results in a clutch friction test, but that difference is important.  o    MA1 has the lowest amount of friction o    MA has a medium amount of friction o    MA2 has the highest amount of friction MA1 and MA oils have a lower amount of friction between the clutch plates which results in more slipping between clutch plates. Slipping the clutch to some degree is important to control power delivery, but I would much rather prefer to rely on my own use of the clutch lever than the oil limit the power delivery. Therefore I prefer MA2 oils, which have the strongest clutch engagement properties. These oils give the least amount of slipping and strongest engagement. Without slipping, less wear and overheating occurs in the clutch so it will extend clutch life as well. Another aspect of an oil that needs to serve as both engine and transmission lubricant is the gear protection. Extreme pressure protection is important to protect gear surfaces from damage in high torque applications. So you should look for an engine oil that provides that protection. -    The concept that a full synthetic oil will make the clutch slip had some truth to it thirty years ago but not in today’s oils. The synthetic base oils and the additives we use today are all evaluated meticulously for their effects on performance and we only use components we know will work in the application we are formulating for. What oil is best for bikes with separate gear oil? -    In the engine, once the issue of the combined transmission is removed, there are a lot more options for the engine oil. In general a friction modified product with friction reducing additives is ideal for this type of situation. Similar to automotive oils, an oil designed just for the engine does not need to include extreme pressure additives so the focus of the formula can be on anti-wear and friction reduction. This type of product generally produces less heat, increases horsepower , and minimizes wear compared to a product designed for a shared sump. The best oil for the transmission is one that enhances the clutch’s performance and protects the transmission from damage. An oil that has good extreme pressure protection without the use of friction reducing additives and a robust additive package to inhibit degradation is the recipe for success for the transmission oil. JASO rated engine oils are typically suitable in this application, but they often have unnecessary components required for the engine that may limit some of the performance in the transmission. If I run full synthetic, can I wait longer before oil changes? -    In general yes. A full synthetic engine oil should provide a higher level of resistance to oxidation. Oxidation of the oil is the main factor in oil degradation so reducing the oxidation rate extends the life of the oil. If you have two identically formulated oils with the exception of one being a fully synthetic polyalphaolefin (PAO) and ester blend and the other being a conventional/mineral product, the synthetic product will often last more than double the time of the mineral before a change is needed. Do I really need a new oil filter every oil change? -    Is it absolutely necessary? Probably not, but I would still suggest it as a good practice.  The filter is there to catch wear particles and contaminants in the oil during circulation. Those contaminants are usually things that promote oxidation and accelerate the overall degradation of the oil. So if you change the oil but leave the old filter in place, you are circulating your fresh oil through the crud that was already filtered out and exposing it to those contaminants right away. By doing this you are immediately accelerating the degradation of the oil before any new contaminants can even make their way into the bike. Alternatively, by changing the filter each time, you are removing those things and giving the bike a fresh start each time and maximizing oil life. I have had an oil brand with the exact same bottle and two different colors, any idea why this would happen? -    Formula changes are pretty common in our industry. We are somewhat less regulated than the automotive engine oil marketplace so we have a little more freedom to go outside the box and develop and change our formulas.  Certain additives are naturally colorful, so they may impart some color to the final formula. So formula changes are one possibility that could change the color. Another possibility is the base oil being used. Common base oil colors range from being as clear as water to as dark as molasses. There are others that have slight green, blue, or red tints them as well. The most commonly used base oils are either clear or some shade of amber, but occasionally those others may be used and they will influence the finished product’s appearance. If everyone is treating the oil with their own additives, does it matter what base oil they start with? -    Base oil selection is important no matter what additives are being used. I’ve always likened it to coffee beans (additives) and water (base oil). If you have some great coffee beans there is going to be a big difference between the coffee made with them using clean spring water or dirty sewer water. Starting with a subpar base oil immediately puts a product at a disadvantage. Likewise, starting with an excellent base oil immediately gives the product a head start. The base oil’s performance is the performance base line and the additives being blended in build on that baseline performance.  There are performance differences within the petroleum base fluid range and there are differences within the synthetic base fluid range. The distinction between base oils is not just between petroleum and synthetics either. There are wide ranges to choose from in both mineral and synthetic base oils with varying quality levels. A well formulated mineral oil will compare very favorably to a poorly formulated synthetic product, so the total formula is important. Focusing on a single component does not give you a full picture of the oil’s performance. Thanks for the info guys!
Posted by Chris Cooksey on Apr 23, 2017

The Beginning of the Journey
I’M BACK! Hello ThumperTalk readers! My name is Scott Meshey. If you’re from the Motocross community there is a good chance you might know me through my blog series from Vurbmoto “Life with the Mesheys”, if not, please check my profile. Get to know me, and I hope you follow along with this blog series. For this entry, I’ll dish out some background and where I am headed right now, kicking off the start of the series. So let’s get to it! My blog series for Vurbmoto ran for 3 and a half years until their recent shutdown. The opportunity to share my experiences through Vurb and now on ThumperTalk is something I truly enjoy. This blog series will follow my progression, good, bad, and everything in between to the pro ranks, sharing my experiences and wisdom I gain along the way. Whether you ride the trails on the weekends, hit the back roads after work, are a serious racer, or a parent of a racer, I hope my experiences give insight not only to just Motocross racing, but I hope they give a unique perspective of the challenges behind the goggles. I want readers to enjoy reading my experiences, but I also want others that aspire to achieve the same goals as myself, particularly the youngsters of the sport, to learn from these blogs in their quest to be the best.  I’ve been riding since I was 4. I started competing at amateur Motocross nationals when I was about 9 or 10 years old, contending at the Loretta Lynn’s Amateur Motocross National 9 years in a row, the Winter National Olympics or “Mini O’s”, the RCSX at Daytona, the Lake Whitney Spring Championship, the Mill Creek Spring Classic, and the JS7 Freestone National Championship. I’ve ridden for several amateur teams, and had the privilege of working with some legends of the sport. In 2016, I jumped into the pro Arenacross series for a few rounds to get experience in the pro ranks. Unfortunately, my experience was cut short by unresolved health problems from a bad case of pneumonia in 2015.    Loretta Lynn’s 2015, Picture by Sarah Behrens Photography  This brings me to where I am today. After hitting the reset button and off the bike for a year, I’m back home in the motocross scene, eager to continue sharing my story and experiences with the dirt biking world, back to good health with amazing people behind me. I’ll be going to Loretta’s for my 10th year in the 250A and Open Pro Sport classes, and jumping into the pro Motocross series thereafter.  Come along for the ride and tap/click the follow button! I’ll see you at the races. Scott Meshey #141  
Posted by Scott Meshey 141 on Apr 14, 2017


Keep blowing gasket between EGR cooler and exhaust manifold
I purchased a new 2008 GMC T7500 in 2010. It has the 6H series 260 hp Isuzu engine. We are full time RV'rs so I had it custom made to tow our 5th wheel and carry our 2 ATV's and 12' aluminum boat. In 2014, 11 months before my extended warranty expired in 2015 it started squealing and eventually blowing the EGR cooler to exhaust manifold gasket when the exhaust brake engages. This gasket was replaced several times then eventually the EGR cooler too. They also discovered moisture from a coolant leak internally, something I complained about for almost 2 years. They eventually replaced the EGR cooler 2 more times as well as the exhaust manifold because the gasket kept blowing, all to no avail. Then they tried a new exhaust brake and that made no difference so put my old one back in. Isuzu engineering suggested custom cutting a copper gasket and some sort of special mounting bolts like they use in racing cars. These also failed recently. They think the bolts are stretching from overheating as they always seem to loosen, but they don't know why. If It was always the same dealer I would say they don't know what their doing, however, I've dealt with 3 different Isuzu dealers in Canada and the US and none of them can resolve this issue. Isuzu can't figure this out and don't want to play anymore so it looks like I may have to take them to court. Apparently I'm the only one on the planet with this issue! Does anyone have any ideas? Thanks
iPad changing website based on orientation
Hi,    I tried searching this but couldn't find anything. I use chrome on my iPad and it allows me to use the desktop site since I prefer it to the mobile site. I have noticed an odd issue however when I tell it to "request desktop site". It will reload the page like it normally does on my android phone but it will still be the mobile site when the iPad is in portrait mode. If I rotate to landscape it's the desktop site and if I got back to portrait, it will go back to the mobile site. I've never seen anything like that on my android phone, or on any of the other websites I request the desktop site for on my iPad. I think once I navigate through the site a few pages from when I first request the desktop site it will stay in desktop mode regardless of orientation.
Good morning All, Any of you use a TWO (2) Bike Hitch Carrier on a 2004 GMC YUKON or CHEVY TAHOE? (Not XL or SUBURBAN). - What is the weight capacity on the hitch and what carrier brand are you using? - Does it work well or do the bikes bounce all over the place? I would rather have a Carrier to haul a small Honda XR100R and a regular size Adult bike, than having to worry about storing a trailer. Thanks in advance.

Dirt Bike

Tilamook state forest- Diamond mill, Jordan creek, Browns camp, Lyda camp RIDING
Hello to any one who is up for riding most weekends in the TSF area. I'm always down to meet new riders who can hang. Hit me up on this topic or pm me if interested. Have been riding with a few guys from tt on the (Portland winter riding topic)and has been great! About me: 34 male intermediate/expert haha 2stroke lover but 4 is ok too, ride with lots of different people on different skill levels ( you don't have to be blazing fast, consistency is key ). LETS RIP!
Eli & Red
Is it possible for a person to actually be allergic to the color red?  
KYB SSS Compression Dampning Input Needed
I have been reading many of the KYB SSS threads and I know I need to make some changes to my forks but would appreciate some input and direction before I dig in and make changes.   Rider- 51yrs old, (riding 42 yrs). 6' 4", 250lbs in street clothes. I enjoy all kinds of riding but prefer difficult single track, trails and hills. (probably B-C Enduro) and C class MX to make matters wors.   I have two bikes with the KYB SSS forks and I have similar complaints about both sets. I really like the forks for bigger bumps and high speed riding but both bikes feel a bit harsh for slower riding when hitting small bumps, roots and rocks.    2007 YZ450F  - I just purchased a near new 2007 YZ450F with about 8 hours of use on it.  I have upgraded the rear spring to a 6.2 and that feels fine.  The forks are completely stock with the compression adjusters all the way loose.  Primary use MX track and fast off road.   2000 GasGas XC300 - I recently replaced the WP43s with 2009 YZ450F KYB SSS forks that are also completely stock with a fresh oil change before I purchased them.  The compression adjusters are all the way loose on these forks too.  (When I purchased the forks they were transported horizontal for 3 hrs and I read that this can cause similar problems. I am not sure if sitting vertical for 4 months and riding the bike for a few hours would have sorted this out or not.) Primary use woods and enduro.   Solutions? Is it possible that with my weight I am blowing through the soft part of the stroke and need to stiffer change springs to make them softer?  The ride height seems about right with the forks set with about 1/8" showing above the top clamp.    Is this something I can address by changing to a thinner / lighter fork oil?   Would the Free Piston Modification help my situation or any combination of the above?   I am not afraid to try revalve them myself, but I am not sure where to start.  I noticed the KYB SSS Offroad post seemed to make a bunch of changes and many ended up back where they started close to stock.    Overall I really like the forks on both bikes but would prefer to make them initially softer and get the compression adjusters off the fully loose limit.   I would greatly appreciate your guidance.


2006 ltr450
Looking at a 2006 ltr450 to trade for my dirtbike and he says it's all stock but doesn't look stock what do you guys think and theses are the only photos I have of it
2003 400ex carb jeting question
so I bought my wife a 2003 400ex ran good for a short time and the head gasket went ive got that all fixed now but it gets hot quick so I got into the carb to find a 38 slow 162 fast and the idle air was still blocked off. the motor has been bored .50 over stock compression it has k&n drilled lid header and fmf slip on I drilled out the block off to the adjustment screw and wanted some advice from someone with more knowledge about what I should jet it at sea level thanks
Eiger top end parts
I have an 2005 eiger 400 and I need a good cylinder for it and can't pay a fortune. Any one got any ideas? I really want to sell it so if anyone wants to buy it and the parts I can build the motor for them? But I really want to know if any one has worked on these and maybe any tips. Thanks.


Help Drz400sm won't start!
Hey guys really need some advice. I parked my bike in the garage the other day running just fine, but today when I went to hop on it it would not start. It turns over like a top, but won't even try to start.  List of things I have tried. i removed the spark plug and replaced it. Also made sure I had spark. i tried spraying starter fluid inside carb with no result.  I removed both the clutch and kickstand safety.  I also just tried roll starting it. It was turning over but once again did not even try to start up. please help I do not know what else to try or check thanks!
1984 Honda Xr200r engine noise
Can anybody help me with this noise? I have the valves in spec.
First Dual Sport Advice
I used to race MX but was a C class rider and just enjoyed riding.  I've ridden on and off since I was 9 years old and started riding a MTB very heavily the last five years.  I've been to Durham town twice this past year and several friends have bikes now.  Long story short I've got the itch.   I have found a brand new 15' FE 350 S for $8850 out the door.  Is this a good deal?   I've looked at a bunch of used bikes everything from KTM 690, DRZ400S, KTM250XCF-W, 350/500 exc, 501s, and WR250R.  I have never really loved riding on the road.  Cars scare me but I would mind communiting every once in a while.  Also the wife is ok with some fuel savings from my truck.   I'm a bigger guy at 6'3" 255 lbs and a little concerned if the 350 will be big enough.  I think I'd like it on the east coast single track though.  I rode my buddies WR250R and that just didn't do it for me.  I rode a WR450F and that was pretty fun and I'm trying to get a hold of my friends DRZ400S.  I know another what should I get thread... I guess I'm looking for reassurance that new 350 is a reasonable deal.  


How many RX1 guys are out there?
I just bough an RX1 this year and can't wait to get on it. Any advice with these machines. First four stroke that I ever bought. Also curious how many miles you guys are putting on them?
2003 KX 250 2 stroke trade for 1999 XCR800 snowmobile worth it?
The XCR800 in good condition and has 2900 miles on it. My KX is in good condition as well. Is this trade worth it? I've always wanted a xcr800
What is this button on a rxl650?
What is this button on a rxl650 it almost dies when I push it?


For Sale: Kawasaki ALL NEW 2017 Kawasaki SX-R 4 stroke 160HP STAND UP
Kawasaki ALL NEW 2017 Kawasaki SX-R 4 stroke 160HP STAND UP Price: $4800 U.S Dollars. Condition: New     Make: Kawasaki Model Year: 2017     Contact us through Email or Text for Purchase: [email protected] Phone Number: +1-510-815-9080 WhatsApp: +1-510-351-9474 Text the Number for immediate reply. Vehicle Description  The all new 2017 Kawasaki SX-R will amaze you.  The most powerful stand up Jet Ski ever produced with DOUBLE the power of the previous Stand Up!  Off the line 0 to 50 meters is FASTER than the Ultra 310R!  148mm three blade stainless impeller hooks up instantly.  The all new V-shape hull offers high stability and superb cornering.  The engine is positioned low and closer to the rider for a confident feel.  The hull sits high in the water, contributing to stability when stopped or moving at very low speeds.  Sponsons contribute to overall stability as well as sharp, clean cornering.  The rider tray has a forward slant to help riders brace against the SX-R's strong acceleration and the raised portion at the rear provides a place to plant your rear foot!  This is ONE AWESOME Jet Ski.  RESERVE YOURS TODAY. ---------------------------------------- Mercury 15 HP 4 Stroke Outboard Motor Tiller 15" Shaft Boat Engine  Price: $1500 USD Contact us through Email or Text for Purchase: [email protected] Phone Number: +1-510-815-9080 WhatsApp: +1-510-351-9474 Text the Number for immediate reply. The large 21.4 cubic inch displacement powerhead of the Mercury 15hp develops plenty of low-end torque, making it an excellent source of power for medium to larger sized jon boats, skiffs, and inflatables. Mercury's multi-function tiller handle, easy auto-ratchet tilt, and vibration-absorbing wishbone mounts are just a few of the exclusive features found on Mercury 15hp models. Specifications Horsepower @ Propeller:    15hp Engine Type:    4-Stroke, 2-Cylinder, SOHC Full Throttle RPM Range:    5000-6000 Displacement:    351 cc (21.4 cubic inches) Bore and Stroke:    61 x 60 mm (2.40 x 2.36 inches) Fuel Induction System:    Single Overhead Cam (SOHC) Ignition System:    Digital CD Ignition w/Electronic Spark Advance Fuel System:    Single Venturi Carburetor Cooling System:    Water-Cooled, Thermostatically Controlled Starting:    Manual Alternator:    Optional 12V 138W 12A (installation required) Gear Ratio:    2.15:1 Gear Shift:    Forward-Neutral-Reverse (shift in tiller handle) Steering:    Tiller Trim Positions:    6 Manual Positions with Auto-Ratchet Tilt Operation Lubrication:    Trochoid Pump Oil Type:    SAE 10W-30 (Mercury 4-Stroke Outboard Oil) Oil Capacity:    1 Quart (1000 ml) Fuel Type:    87 Octane (up to 10% ethanol content) Fuel Tank (integral):    No Fuel Range:     External Tank Ready:    Yes includes 6.6 Gal. Fuel Tank + Quick Connect Fuel Line C.A.R.B. Rating:    Ultra-Low Emission (3-STAR) Saltwater Rated:    Yes Shaft Length:    15"  (Shaft Size Help) Weight:    111 lbs (50 kg)
I have a 2001 honda xr200r that just got a fresh top end rebuild. I've cleaned the carb 5 times re-timed it 3 times including checking valve clearance and it does not run properly. I've even noticed it blowing out exhaust or air through side of air cleaner. Any idea on what's going on?
2017 SX-R Jet Ski
Kawasaki had the new 2017 SX-R Jet Ski at the Toronto Motorcycle Cycle show this weekend. It has a1500cc 4 cylinder in-line 4 stroke engine. It looks awesome!

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