Paul Olesen

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About Paul Olesen

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    TT Powertrain Expert

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    Racing motorcycles, engine design, homebuilt motorcycles, engine building, traveling, flying, backcountry snowmobiling, water sports, downhill mountain biking, reading, and films

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  1. With warmer weather and the riding season around the corner for many of us, I wanted to cover a topic that can either make or break an event. Whether you’re competing in a racing series or traveling to the track or trail, let's talk about event preparedness. More specifically, what spare parts should you keep on hand? Plus, what methods do you use to keep your spares organized? Honestly, I struggled with organization until I started working on this post. I had no method to my madness. Every time an event came up I’d do the same thing; throw a bunch of stuff in a box or the back of my van and head to the event. The sad part is I now realize this was a weakness of mine for quite some time, but didn’t do anything about it! Maybe you can relate? I finally said enough is enough. I don’t throw my tools in a cardboard box when I go to a race, leaving what I bring to the fate of my memory. So why would I do that with the spare parts I bring? I started solving this problem by compiling a spreadsheet detailing what spare parts I keep on hand for ice racing and hare scrambles. I realize that each discipline will differ and may have niche parts that should be kept. The goal here is not to definitively define what spares one should keep on hand, but to have a conversation and provide a resource that can be used to help people get set up based on their own needs. Once I took inventory of everything I felt I wanted to bring to a race, I went to Menards and went hunting for the perfect organized storage bin/toolbox. Here’s what I ended up with: Naturally, once I returned with the toolbox, my list grew and I probably need to go back for a bigger one. I intend to store a copy of the spreadsheet in the tote so I can keep tabs on inventory and know exactly what I have available. Should I get another bike, this system is easily replicable and my plan is to get another organized toolbox that goes with it. This system is how I went from being an unorganized “throw it in the van at the last minute” rider to a more relaxed well prepared rider. I’d love to hear how you handle event readiness, what you bring, and how you keep track of it. My hope is that by sharing our strategies we’ll save someone the misfortune of having a bad day at the track or trail. Perhaps I'll even end up with more things I need to add to my list. -Paul If enjoyed this post be sure to follow my blog and sign up for my newsletter! DIY Moto Fix Newsletter
  2. Did you incorporate the pipe hanger tape when you tried or just a hose clamp? Also, for a two-stroke I agree using your fingers is the easiest way. The method I've outlined is more useful when dealing with oil control rings.
  3. Personally, I've not had any problems with uneven tightening or the worm gear stripping the band using the method I've presented, however, that does not mean it is the only method. The point of this article was to present an option and allow folks to weigh in with other ideas and tips and expand the topic from there. I think the clamp you've proposed would work equally well and gives everyone another avenue to pursue. To your point it's possible the T-bolt clamp you've suggested would be a better solution for applications where the ring tension is high.
  4. DIY Piston Ring Compressor

    Today I want to share a quick tip with those of you who are working on your own engines but just can’t justify buying a set of piston ring compressors. It’s entirely possible to make a perfectly good ring compressor from materials you can get at the hardware store. All you need is some plumber’s pipe hanging tape and a hose clamp that is sized according to your cylinder bore. To construct a DIY ring compressor from plumber's pipe hanger tape you will need to determine the length of tape required. This is easily done using the following equation for calculating the circumference of a circle. Length of Tape Required = Piston Diameter x π (Pi) When the tape is wrapped around the piston tightly, the final length may need to be reduced slightly so that the ends don’t butt together. Once the tape has been cut to length, make sure whichever side of the tape will be contacting the rings is smooth and free of little plastic burrs that could catch the rings. Simply lube up the tape, tighten down the hose clamp, and you are in business. Do you have a tip that makes compressing rings easier or cheaper? If so, leave a comment below! - Paul If you enjoyed this tip and want access to more like it, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. On the fence about the book? Check out what other riders are saying: Thumper Talk Review Available at:
  5. Help! - Bike Only Starts When Pushed

    Today I want to talk about a situation I hear all too often. Someone’s bike, whether it be a two-stroke or four-stroke, only starts when it is pushed. Before I discuss potential causes for this scenario, take a moment to think through the situation yourself. What mechanical factors would result in either a two-stroke or four-stroke only starting when it is bump started? In either case, the reason the engine is able to start when it is push started is because it is able to build more compression than it otherwise could when it is kicked or the electric starter is engaged. More compression is achievable because the cranking RPM is higher than what’s possible with the aforementioned starting methods. With a higher cranking RPM for a four-stroke, more air will fill the cylinder on the intake stroke, and for a two-stroke the scavenging process will be improved. With this being the case we must look at reasons why the engine is struggling to build compression in the first place. Starting problems specific to four-strokes: 1. Valve seat recession - When a valve seat wears out and recedes, the valve moves up towards the camshaft. This leads to diminished valve clearances and if left to run its course, the valve and shim will bottom on the camshaft’s base circle. This can prevent the valve from seating and make the engine hard to start. 2. The valve is bent - A valve with a serious bow to it may get jammed up inside the guide and not return all the way back to its seat. Bent valves typically result from an over-revved engine where the valves contact the piston. Valves can also bend to a lesser extent if they were mated to valve seats that were not cut concentrically to the guides, or they were paired with worn seats. 3. The valve stuck in the guide - This is usually due to the engine overheating. When the engine overheated the clearance between the valve and guide diminished which caused metal to transfer from one part to the other, ultimately ruining the surface finish on one or both parts. Once this happens the valve may be prone to sticking in the guide until the engine warms up. 4. The valves and seats do not seal well - Worn valves and valve seats can compromise the seal between them. Valve and seat wear is a natural part of running an engine but can also be accelerated by ingesting dirty air. Starting problems specific to two-strokes: 1. The reed valve is worn - Reed petals that don’t close all the way, are chipped, or bent will not allow sealing of the crankcase and efficient gas flow up from the crankcase into the cylinder. 2. An engine seal or gasket has failed - A two-stroke engine requires a well sealed crankcase and cylinder in order for it to scavenge gases efficiently. A worn crank seal, leaky base gasket, or problematic power valve seal can all make starting more difficult. Two and four-stroke problems: 1. The piston rings are worn - Worn piston rings will allow compressed gases to escape past them. 2. The head gasket or o-rings are leaking - Usually a leaking cylinder head will be accompanied by white smoke if coolant is being pushed into the combustion chamber, by coolant being blown out the radiator, or both. I hope you found this rundown of potential problems useful for diagnosing bikes that like bump starting over a kick or the push of a button. Can you think of any other problems that would lead to lack of compression? If so, leave a comment and share them. If you liked this post and want more technical info, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. In it you will find over 300 pages of technical knowledge to help you get off on the right foot when rebuilding! - Paul Amazon
  6. Help Moto Mind Help You + A Quick Tech Tip

    I hope you all had a good holiday season and are excited for 2017. The ice bike has been kicking my butt so far, but I’m thankful I’ve been able to get out and ride. I’m definitely excited for the new year and today I wanted to discuss my upcoming blogs and share a quick tech tip with you. My blog post pool is low right now and I’d like your help! Looking ahead to 2017 I want to deliver informative posts tailored to what you need to know and want learn. In the comments section below be sure to share your thoughts on what you’d like to learn about this year. Whether it’s maintenance, tuning, suspension, two-stroke, four-stroke, or anything else-- I want to hear what you have to say. Depending on post length it takes me anywhere from 2 - 5 hours to write a piece I feel comfortable publishing for you, so I want to make sure I’m spending my time covering topics that are truly beneficial and relevant. Moto Mind Quick Tech Tip Anytime you drain fluids from something you’re working on and halt progress (think waiting for parts) tag the throttle or any other visible location and note that there’s no fluid in the machine. This isn’t always applicable but here’s an instance of when it was. I’ve moved a few times in the last couple years and during that transitional period my bikes were five hours away in northwestern Wisconsin. One weekend I was set to make the trip back home to go riding, certain that my bike was ready to go. I got there and found that I’d left myself a tag noting that I was only part way through the oil change I so vividly remember completing. While I usually check my sight glass anyway, I can’t say I always do, especially if I’m in a hurry. Whether or not I would have caught the lack of oil without the tag I will never know, but I’m just glad I left myself a visual reminder. If there’s something you’d like to learn about, please leave a comment below and I’ll see what I can do to work it into this year’s blogging schedule! Plus, if you got socks or other stuff you didn't want over the holidays, be sure to check out my book and treat yourself! Amazon - Paul
  7. Thanks, glad you liked it.
  8. Thanks for your comments GDT!
  9. Thanks for your comment. I absolutely agree and am glad you brought this point up.
  10. I hope you’re all enjoying the fall weather. For those of you in northern states, I hope that you’re getting in some end of season riding. This month I want to touch on bolted joints and the importance of adhering to tightening techniques outlined in your model’s service manual. How A Clamped Joint Works I’m going to discuss the importance of criss-cross patterns, tightening sequences, incremental steps, and joint lubrication but first I want to explain how a bolted joint works. As a bolt is tightened to secure a pair of parts, the bolt will stretch a very small amount. The stretch in the bolt creates tension or preload in the joint which is the force that keeps the joint together. The amount of preload created is dependent on bolt size, bolt material, the torque applied, and the friction between the threads. There are additional variables, however a discussion on bolt engineering would be very long and not all that exciting! As long as you understand the basics for engine building you can begin to appreciate the importance of correctly tightening fasteners. As you are well aware, an engine consists of many parts fastened together. What you may not consider as much is that the majority of these parts are fastened by more than one fastener. This means that how much you tighten/preload one fastener will have an effect on the surrounding fasteners. This interaction between the fasteners begins to shed light on why tightening sequences are so important. The evenness of the preload across the bolts securing a part can affect part life. Warpage can occur in parts which are improperly tightened, ultimately rendering the part useless. A prime example of a part that can warp is a four-stroke cylinder head. If the bolts are unevenly tightened over time, the cylinder head can become permanently distorted. Gasket sealing problems can also occur from improper preloading of bolts across a part. In order for a gasket to seal it must be evenly compressed. If one area of a gasket is highly compressed and tensioned while another area is not, the gasket can easily leak through the low tensioned area. In the case of plain bearing bores, such as the cam cap, uneven preloading may cause the bearing bore to distort. As a result the cam may become difficult to turn. Or if run, the cam bearing bore will wear unevenly and in severe cases the cam could seize. While ensuring bolt preload is even can be a problem there are three tightening techniques that virtually eliminate the issue. If you’ve been building engines for any length of time you’ve probably already been utilizing these techniques. Hopefully now you may have a better understanding of why the service manual instructs you to tighten parts a specific way. Criss-Cross Patterns Criss-cross patterns are called out when tightening or loosening parts with a simple square pattern or circular bolt pattern. These basic patterns have been around for a very long time and are a proven method for evenly distributing clamping load across a part. Most cylinder heads will utilize this type of clamping pattern. Tightening Sequences For more complex bolt patterns, such as those found on cam carriers and crankcases, the manufacturer will usually identify a specific sequence for tightening and loosening the fasteners. This sequence is based on testing and the past experiences of the manufacturer. Incremental Steps Highly torqued bolts, such as those found on the cylinder head, are almost always tightened and loosened in incremental steps. An incremental tightening sequence consists of torquing all the fasteners to a specific torque value, then increasing the torque and tightening again, and finally arriving at the final torque value. This sequence is typically performed in two to three steps. Here’s something important to keep in mind regarding incremental steps! When torquing bolts in steps the change in torque between the steps must be large enough to induce bolt movement. For example if a bolt was torqued to 35Nm at the first step and the second step was 38Nm this would not be enough of a change to make the bolt move at the second step. The torque wrench would not overcome the friction of the stationary bolt and would hit 38Nm before the bolt even moves. As a rule of thumb incremental changes should be no less than 5Nm and if possible should be greater. Lubrication For highly torqued fasteners often times the service manual will specify that the threads of the fastener must be lubricated. The lubricant can be as simple as fresh engine oil or a specifically formulated thread lubricant product. Adhering to any lubrication guidelines is of utmost importance. Since we most commonly measure torque to determine whether a bolt has been tightened/preloaded enough any change in the amount of force required to turn the bolt will influence the resulting bolt preload for a given torque value. The force required to turn a bolt is partially dependent on the amount of friction in the joint. If we had two identical fasteners where one was lubricated and the other was not, and we set the torque wrench to the same value for each, then both were tightened, the resulting bolt preload would be different between the two. Due to the reduced friction in the lubricated joint the bolt would stretch more and the preload in the joint would be higher at the specified torque wrench setting than the unlubricated joint. Depending on the criticality of the joint this can be a really big deal! It also shows why in some applications (think two piece conrods) directly measuring bolt stretch is a more accurate means of determining bolt preload. I hope you enjoyed this quick summary of tightening techniques and their importance! If you have tips of your own you’d like to share or other pearls of wisdom please leave a comment. For those of you interested in more engine building knowledge check out my book, The Four Stroke Dirt Bike Engine Building Handbook. You’ll find more detailed and comprehensive info on engine building there. Simply follow the links below. Thanks for reading and have a great week! -Paul The Four Stroke Dirt Bike Engine Building Handbook Available on Amazon
  11. Do You Know How To Properly Inspect a Clutch?

    Having a clutch that works correctly is key to being able transfer all the power your engine produces to the rear wheel (or wheels if you're a quad guy/gal). In this post I want to share some key clutch inspection techniques I use and recommend to help ensure your clutch works as it should. These tips are presented in a step by step format and are taken right from my book, The Four Stroke Dirt Bike Engine Building Handbook. Basket Inspection Inspect the driven gear which is secured to the basket. Look for damaged gear teeth and other imperfections. Grasp the gear and basket firmly, then try to twist the gear. The gear is secured to the basket either with rivets or fasteners. With use, the rivets or fasteners can loosen causing the gear to become loose. Most baskets use round rubber dampers to locate the gear to the basket, which are sandwiched behind the backing plate. The dampers can wear out and break, which will create excessive play between the gear and basket. Any looseness may have been accompanied by excessive gear noise or rattling sounds when the engine was previously running. On baskets with loose gears and riveted backing plates the corrective action which will need to be taken is to either replace the basket or drill the rivets out. The idle gear may need to be pressed off in order to remove the backing plate. Once this is done, holes can be tapped and bolts installed which will secure the gear in place. Any rubber dampers that have worn can be replaced with aftermarket options. Check out this article for more details on clutch basket damper replacement: How to repair your clutch basket dampers for less than $30. Inspect the needle bearing bore surface on the basket next. Run your fingernail across the bore feeling for signs of wear. The bearing surface should be smooth and free of imperfections. If the surface is grooved or worn the basket will need to be replaced. Inspect the area inside the basket where the large thrust washer resides. Wear should be minimal in this area. If any grooving is present, the needle bearing and spacer the basket rides on may have worn causing the basket to wobble or the pressed in steel insert has backed out, ultimately causing the face of the basket to rub on the edges of the washer. Check for bent clutch basket fingers on the basket. Then look for grooving on the basket fingers where the clutch discs come in contact with the fingers. Grooving is caused by the clutch discs slamming into the clutch basket fingers. Normally grooving will be more pronounced on the drive side fingers. Grooving is not abnormal and occurs through usage of the clutch. If any grooving is present, use the end of a pick to evaluate how deep the grooves are. Any grooving that can catch the end of the pick is also likely to be able to catch the edge of the clutch discs. When this happens, the clutch will have difficulty engaging and disengaging. If your bike had clutch disengagement/engagement problems prior to disassembly, basket grooving is the most probable cause. A file can be used to smooth the grooves so the discs no longer catch, however deep grooving is an indication that the basket is near the end of its life. When filing clutch basket fingers, attempt to remove as little material as possible and remove material evenly from all the fingers. Some manufacturers provide a specification for the clearance between the clutch disc tang and the basket fingers. This clearance can be measured by temporarily installing a clutch disc into the basket and using a set of lash gauges to check the clearance between the two parts. Both the clutch disc tangs and basket fingers will wear so if the clearance is outside the service limit it may be possible to prolong the life of the basket by installing new clutch discs. This is a short term fix however, and replacing both components at once is advisable. Bearing/Spacer Inspection Inspect the clutch hub needle bearing and spacer for signs of wear. The needle bearing will be replaced with a new bearing, but if the spacer is in good condition it will be reused. Check for grooving or concavity along the surface of the spacer where the bearing rotates. While the needle bearing won’t be reused, it can be inspected as well to help confirm any problems associated with the clutch basket or spacer. Hub Inspection There are two main areas on the clutch hub which will wear. First, grooving can occur on the splines which locate the clutch plates to the hub. The grooves are a result of normal clutch use and occur when the steel clutch plates rotate back and forth in the spline grooves. Any grooving which catches the end of a pick should be considered problematic. Careful filing to smooth the grooves or hub replacement are the two options available for remedying the issue. The clutch plates must be able to easily slide back and forth along the hub, otherwise clutch disengagement/engagement problems will occur. The second area susceptible to wear on the clutch hub is at the back face of the hub. This is where the outer clutch disc contacts the hub. When the clutch is engaged, the clutch disc and hub will rotate in unison. However, when the clutch is partially engaged or disengaged, the clutch disc will rub against the face of the hub causing both the hub and disc to wear. Look for uneven wear patterns and indications of how deep the clutch disc has worn into the clutch hub. If the face of the clutch hub has worn excessively or unevenly, the hub should be replaced. Pressure Plate Inspection The interaction between the pressure plate and clutch disc is identical to the situation previously described between the clutch disc and clutch hub. Wear will occur on the face of the pressure plate which contacts the outside clutch disc. Determine the condition of the pressure plate by looking for signs of excessive or uneven wear on the face of the pressure plate. Disc and Plate Inspection Both the clutch discs and clutch plates are designed to be wear items which will need replacement from time to time. Thickness and straightness are the primary inspection criteria used to determine if either component requires replacement. If there are any problems with any of the discs or plates replacing them as a set is best. Clutch Disc and Clutch Plate Inspection Clutch discs are made out of various compositions of fibrous materials which wear at different rates, while clutch plates are made from steel. Service manuals will specify a minimum thickness that the clutch discs and plates can be. This thickness can easily be measured by using a caliper. Take measurements at three to four locations around the clutch disc or plate to confirm either has not worn unevenly. Once all the disc and plate thicknesses have been measured, both should be inspected for warpage. This can be done by laying the disc or plate on a surface plate or other flat surface. A set of lash gauges are used to determine any warpage. The service manual should specify a maximum warpage value which is usually around 0.006” (0.15mm). Attempt to insert the 0.006” lash gauge underneath the clutch disc or plate at multiple points. If the feeler gauge slides beneath either of the parts, those parts are warped and should be replaced. Clutch discs which have been overheated due to excessive clutch fanning by the rider, not only may warp, but also emit an unpleasant stinky burnt smell. If a noticeable smell is present, the discs have overheated and should be replaced. Likewise, clutch plates that have overheated will likely be warped and exhibit discoloration. The discoloration is a sign of excessive heat build up. Once the clutch plates have overheated, the material properties of the plate change, the hardness is reduced, and the plate becomes less wear resistant. This means discolored plates should be replaced. Lastly, inspect the clutch disc tangs for wear, chipping, or damage. If any tangs are damaged the disc should be replaced. Clutch Spring Inspection Over time and due to normal clutch use, the clutch springs will shorten. Clutch spring minimum free length specifications are provided by manufactures and can easily be measured using a caliper. Clutch springs that are shorter than the minimum spec provided by the manufacturer will not have sufficient spring pressure to keep the clutch from slipping under heavy loads. Any springs at or past their service limits require the replacement of all springs as a set. This way when the new springs are installed, even pressure is applied to the pressure plate. I hope you enjoyed this passage from my book detailing clutch inspection. If you have additional tips you'd like to share please leave a comment! If you want more technical DIY dirt bike engine information, learn more about the book on our website or on Amazon. Simply follow the links below! The Four Stroke Dirt Bike Engine Building Handbook Amazon Store Thanks for reading! -Paul
  12. Thanks guys, glad you enjoyed it!
  13. This month I wanted to share an exert from the Race and Performance Engine Building chapter in my book, The Four Stroke Dirt Bike Engine Building Handbook. If you've been wondering how high compression pistons work and if they are right for your application, read on! Piston upgrades are normally considered when changing the compression ratio is desired or larger valves are installed. In both instances the shape of the piston is altered either to reduce the volume in the combustion chamber or to allocate additional room for larger valve pockets. The compression ratio defines how much the original air/fuel mixture which was sucked into the engine is compressed. The following equation shows how an engine’s compression ratio can be calculated. The swept volume is the volume that the piston displaces as it moves through its stroke. Mathematically this volume can be determined using the following equation. The clearance volume is the volume of the combustion chamber when the piston is at top dead center (TDC). While manufacturers specify what the compression ratio should be, due to subtleties in manufacturing, parts vary slightly from engine to engine so finding the exact clearance volume of your engine actually requires measuring the clearance volume. Undoubtedly you have probably heard that raising the compression ratio will increase the power of an engine. This is definitely true, however you should be aware of the other consequences that come along with this. The more the air/fuel mixture can be compressed before it is combusted, the more energy which can be extracted from it. The reason for this is due to thermodynamic laws. In summary, the temperature difference between the combusted mixture when it is hottest and coolest determines the power and efficiency of the engine. The hottest point of the mixture will arrive shortly after the mixture has been ignited and the coolest point will occur around the point where the exhaust valves open. Since the temperature of a gas increases as its volume decreases, it is easy to see how increasing the compression ratio increases the overall combustion temperature. Something less obvious is that because the gases are compressed more, they will expand more and actually be cooler by the time the exhaust valves open. If increasing the temperature of the compressed mixture is good, you might be wondering what keeps us from raising it higher and higher. Detonation, which is a by product of the additional heat and pressure in the combustion chamber, is the main reason the compression ratio can’t be increased beyond a certain point. Detonation occurs after the spark plug has ignited the air/fuel mixture. Normally once the spark has ignited the mixture, the flame will propagate outwards from the spark plug evenly in all directions. When detonation occurs some of the remaining air/fuel mixture situated towards the edges of the combustion chamber spontaneously combusts before the flame reaches it. When this happens a large spike in combustion pressure occurs. If severe enough detonation can cause engine damage in the form of pitting on the piston crown, broken ring lands, and scuffing of the piston from overheating. To combat detonation there are a few different parameters which can be tweaked to help alleviate the problem. The air/fuel ratio can be altered along with the engine’s ignition timing to change the peak combustion temperatures, a fuel with a higher octane rating can be used which will be more resistant to detonation, and upgrades to the cooling system can be carried out to help keep the combustion chamber cooler. Along with increasing the likelihood of detonation as a result of increasing the compression ratio, the engine will also produce more heat. The cooling system must absorb this additional heat and be able to adequately cool the engine, otherwise overheating and detonation may be problematic. Radiator size, thickness, and the speeds at which you ride at all play a big role in how efficiently the cooling system operates. Now that you have an understanding of how high compression pistons affect performance, you can consider if this will be a good modification for you. Aftermarket pistons are usually offered in a few different compression ratio increases. You will want to look closely to see if any high octane fuels will be required to use in conjunction with the piston and if any cooling system improvements are necessary. For racers looking to extract all the power from their bike, adding a high compression piston is one of the things that will be necessary. If you do a lot of tight woods riding, hare scramble racing, or enduros where low speeds are the norm, you may want to shy away from raising the compression ratio as the cooling system will have difficulty dealing with the increased heat at low speeds where airflow is limited. I hope you enjoyed this excerpt on piston modifications and how they affect an engine. If you liked this write up and are interested in learning more about performance options and four stroke engine building, pick up a copy of my book. Right now the book is on sale at 20% off our list price when you order within the next two weeks. You can grab your discounted copy off our site here: The Four Stroke Dirt Bike Engine Building Handbook Or on Amazon: Amazon Book Store Thanks for reading and have a great week! -Paul
  14. Thanks for the additional tips and comments!
  15. Air Filter Maintenance - What You Need To Know In my last post I shared an account of what happens when dirt gets past the air filter and into an engine. This was a telling tale, however I want to go further and discuss key components of what can be done in terms of maintenance to limit the chances of sucking in dirt. Whether you ride a two-stroke or four-stroke, it makes no difference, the importance of keeping dirt out cannot be overstated. I want to start off by thanking those that left constructive comments in my previous post. Your insights into filter maintenance are much appreciated and help reinforce what I’m about to share. How often should I change my air filter? This depends entirely on the conditions you ride in. Dusty dry conditions will warrant more frequent filter changes than a damp riding environment where dust is non-existent. The amount of dirt accumulation that is acceptable is subjective, but I always err on the safe side. As an example, my filters are blue when freshly oiled and as soon as they start to become blotchy and start to turn color I change them. Can I change my air filter too often? Yes and no. I say yes only because every time the filter is removed there is a chance for dirt to enter the engine. A sensible changing regimen decreases the odds of dirt getting into the engine as the filter is removed/installed. What to Use I’ve personally been using FFT filter oil, however, there are many great options out there. No Toil’s water based oil system is something I’ve heard good things about and would like to try too. Asking other riders or doing a quick search will certainly turn up more great options as well. Removing the filter The main point I want to mention here is to be careful when removing the filter from the airbox so that dirt does not come off the filter or surrounding areas and find its way into the intake. On most bikes, fitting the filter between the subframe is a tight fit and dirt can occasionally come off as the filter is pulled up. To help prevent this, clean the subframe or any areas the filter is likely to contact prior to removing it. Also watch for dirt accumulation at the top of the filter between the sealing flange and airbox. Airbox Cleaning Prior to any cleaning efforts be sure to use an air box cover or stick a clean rag in the intake tract which will help ensure any dirt that is dislodged won’t make its way into the engine. Filter Cleaning The correct way to clean a filter depends entirely on the type of oil used. Petroleum based oils will require a two step cleaning process. First a solvent must be used which removes the majority of the dirt. Second, the filter must be cleaned in soapy water and rinsed. Water based oils only require a one step cleaning process using soapy water or a water based filter cleaner. Selecting Solvents for Cleaning Away Petroleum Oils Air filters consist of multiple foam elements which are bonded together chemically with adhesives. Depending on the adhesives used in the filter, certain solvents may or may not react. If a reaction occurs, the joint can break down and the filter can be ruined. When selecting a solvent, it is always a safe bet to follow the recommendations provided by the filter manufacturers. However, as many will point out through their own experiences, there are several potential solvents that can work in place of the manufacturer’s. A quick forum search will surely result in an overwhelming number of hits on filter cleaning and potential solvent solutions. I personally use parts washing fluid which I've downgraded from the washer to a bucket. Cleaning Technique The biggest tip I can share here is to make sure you only squeeze the filter when cleaning, don’t twist it. Squeezing lessens the likelihood of the glued joints getting damaged. Filter Oiling The goal is to get complete uniform saturation without over oiling. This can be done a number of ways and is largely dependent on the method of application (rubbing in by hand, dunking in oil, spray on, etc.). My preferred method is to dispense oil from a bottle and work it in by hand. I believe this process keeps the amount of excess oil at bay, isn’t too messy, and it’s relatively easy to get good uniform saturation. Many filters have two stages, a coarse foam filter element good for trapping large particles and a fine element suited for trapping smaller contaminants. Be sure to work oil into both elements. Remember when working the oil in to be gentle with the filter. Rub and squeeze but don’t twist. Once the filter is saturated with oil remove any excess by carefully squeezing the filter. Ideally, very little excess oil should get squeezed out, but remember, this is entirely dependent of how generous oil was applied. After excess oil has vacated the filter a nice even thin layer of oil should be visible. Batch Filter oiling is a dirty job. No matter how hard I try, oil always seems to end up where I don’t want it. To make things messy less frequently, batch the filter cleaning and oiling process. Buy a few filters, oil them, use them, clean them, and then repeat the process all over again so the task isn’t done as regularly. Keep the pre-oiled filters in Ziploc bags so that they’re ready to go when you need them. Greasing the Flange Is it necessary? I believe the directive to grease the flange of the filter may have originated long ago when the sealing flanges of filters were not predominantly foam. Nowadays whether grease is necessary or not is mostly personal preference accompanied by whether or not the filter cage and airbox seal flat to one another, and how tacky the oil is that is being used. Personally, I still use a waterproof grease on my filter rims, however I’m aware it is probably not necessary in all circumstances. Installation Keeping dirt off the freshly oiled filter during installation is the main challenge. There are a few helpful tips I can share for doing this. First, make sure the bolt is installed in the filter cage! It’s frustrating when you forget it. Once you’re ready to install the filter I find that rotating the filter 90 degrees to its normal direction so that it can more easily be slipped past the subframe makes things much easier. Once down in the airbox the filter can be rotated into position. The other option is to use a plastic bag as a shield effectively covering the filter while it is being lowered down. Once in position the bag can be removed. Wrap Up I hope you’ve enjoyed my post on air filter maintenance. If you have any questions or comments please share them below! For those of you interested in all things engine related check out my book, The Four Stroke Dirt Bike Engine Building Handbook for more awesome information. In honor of Independence Day we’re having a two week sale where you can save 15% by entering offer code july4th at checkout if you order before July 17th. Thanks for reading! -Paul