Standard MX vs. O-Ring: How To Choose the Proper Chain for your Bike

Many engine failures can be potentially prevented by knowing what signs to look for when maintaining your 4-stroke. We put together 10 tips to help you know when your engine may need a little extra attention.
All too often in the motorsports community we here stories of engines blowing up in spectacular fashion. These are gut wrenching tales of catastrophic engine failures that are often shared among friends, online, and bench raced as a form of universal currency. Whether its a rod exiting through the side of a crankcase, valves imprinting into the piston, or any other major catastrophe, these events illicit fear, confusion, and gratitude among engine owners. Fear that a similar event could happen to them, confusion as to how a massively destructive failure happens in the first place, and gratitude that it is someone else’s problem.

Nobody wants to end up with a piston looking like this. That's why we put these tips together to help you know when your 4-stroke engine might need some preventative maintenance.
We’re going to discuss things that can be done preventatively to your four-stroke engine that will greatly reduce the likelihood that you’ll be on the storytelling side of a major engine blow-up experience. Contrary to what you may have been led to believe, engines don’t often suffer catastrophic failures for no apparent reason. There are exceptions, such as running an engine with a defective part, but it’s not the norm. Engines will willingly exhibit a number of signs that failure is around the corner. Being willing to “listen” to your engine and taking the time to perform routine maintenance checks is often all that’s necessary to prevent an expensive disaster.
We’ll start by reviewing a handful of observation opportunities that can be checked with the engine running, then we’ll get into some things that can be checked diagnostically. 
Startability
Does the engine struggle to start when kicked, but is more prone to coming to life when the electric start is used, or when the machine is bump started? Poor starting under normal conditions is not an inclusive sign that the engine is doomed to a spectacular failure, but it is a sign that something is amiss. Carburetion or injection issues are possible, but the bigger potential issue to be aware of resides within the cylinder head. 
Low Compression
Lack of compression usually correlates with startability issues. Valves or piston rings that are no longer seating properly may be the cause of the poor startability characteristic. When the valves or piston rings don’t seat properly, the engine doesn’t build good compression, so when kicked, the engine struggles to come to life. Push the machine or use the electric start, and the compression event is shortened via faster rotational speeds, which may be just enough to bring the engine to life. 
Take notice of how it feels when kicking it through. When you feel less resistance through the kick starter, almost as if you could kick it with your hand, the valves are too tight from wear on the valve train. In some cases, this can be solved with a valve adjustment using a shim kit. However, there's a good chance more items in the head are worn out and need attention.

Sometimes tight valves and low compression issues can be temporarily solved with a valve adjustment, but there are most likely more worn parts that need attention.
Find replacement valvetrain components.
Crankcase Breather
On many engines, the crankcase breather is vented to the airbox. Oil accumulation in the airbox or observation of a large amount of oil mist blowing out the breather when the engine is revved, is a justifiable concern (the exception is if the bike spent some time running on its side) and should necessitate further investigation. Typically, higher than normal pressures in the crankcase are the cause of oil blowing out the breather. Higher than normal pressures can be the result of poorly sealing piston rings, which allow combustion pressure into the crankcase.

Keep an eye out for oil exiting the crankcase breather hose, as this is commonly the result of higher than normal pressures, which could mean the piston rings are not sealing properly.
Smoke After Warm Up
Blue smoke exiting the exhaust pipe after the engine has warmed is a sign that oil is burning in the combustion chamber. Oil can enter the combustion chamber past the valve stem seals or pistons rings, so if this symptom persists then one of these components may be compromised. White smoke exiting the exhaust pipe after the engine has warmed is a sign that coolant is burning in the combustion chamber. The root of this problem is typically a leaking cylinder head gasket. Find gasket kits and top end components.
Excessive Coolant Exiting the Overflow Tube
While it is common for coolant to exit the overflow tube when the bike has been tipped over or when it has overheated, it should not occur regularly. Coolant blowing out the overflow tube is another good indicator of a leaking head gasket.

Most coolant overflow tubes will lead down and out from underneath the bike. Keep and eye out for steaming coolant coming from the tube. This can be a sign of a bad head gasket if you're not in an overheating situation.
Coolant Weepage
Dribbles of coolant exiting the engine around the coolant pump are indicative of a faulty water pump seal. If left unattended, the entire cooling system will eventually empty, causing overheating and an incredible amount of damage. 

Check around your water pump after operation to make there is no coolant weeping out because of a bad gasket/o-ring. Coolant loss can lead to overheating, which can result in serious engine problems.
Excessive Top End Noise
Due to all the moving componentry found within the top end of a four-stroke engine, mechanical noise is often present. Discerning what is normal takes a trained ear and familiarity with the particular engine in question, however, audible cues often present themselves when components wear or clearances loosen up.
Cam chains whirling around will have a metallic noise associated with them. The intensity of the metallic noise may increase as the cam chain stretches or if the tensioner is not keeping enough tension on the chain. Valve train noise is rhythmic and can increase in intensity as clearances change and as the valve seats and valve faces wear together.
Find OEM quality cam chains and more.

he intensity of cam chain noise will increase if you're chain has become too loose for the tensioner to keep proper tension on.
Now that we’ve covered some of the live engine observations that can be made, let’s shift gears and discuss some more intrusive diagnostic assessments we can perform.
Engine Oil
The composition of the engine oil can provide a lot of clues as to what is happening within the engine. For starters, what color is it and what is in it? Oil that appears milky is a good indicator that moisture is finding its way into the oil system. The most common culprit is a faulty oil side water pump seal. Extremely black oil may be due to poor maintenance practices on account of the owner or via combustion byproducts entering the oil stream at an abnormally high rate. Worn piston rings can be held accountable for letting in combustion gases and byproducts.
A keen eye can spot various metallic particles within the oil itself. Aluminum will appear silvery gray. Bronze particles will have a gold shine. Ferrous particles will be dull and are often more discernable by dragging a magnet through the oil. Accumulation of all of these aforementioned particles will be normal in small quantities, however, excessive amounts of any of them could be cause for concern.

Keep an eye out during oil changes for mettalic particles, particularly dark color, and a milky look.
Engine Coolant
Coolant contaminated with black specks can often be traced back to a leaking head gasket. Combustion byproducts are forced into the coolant system due to the high pressures in the combustion chamber during the combustion event. These black specks will often float and show themselves as soon as the radiator cap is removed. 

Check your coolant for black specs, as that is often an indicator of a bad head gasket.
Leak Down Testing
Performing a leak down test on an engine is by far the most definitive diagnostic procedure that can be performed to determine the health of the piston rings, cylinder bore, valves, valve seats, and head gasket. If any of the previously mentioned symptoms are observed, a leak down test is almost always a great next step.
A leak down test pressurizes the engine’s combustion chamber and compares the amount of pressure going into the combustion chamber to the pressure that is retained. Pressurized air is administered via the spark plug hole and two pressure gauges are used to make the comparison. The piston is positioned at top dead center on the power stroke. Air exiting the combustion chamber can then be traced back to the valves, head gasket, or piston rings.
Find OEM+ quality piston kits and more top end components here.

Performing a leak down test is a great indicator of the health of your piston rings, cylinder, head components, and gaskets.
Many of the problems discussed here are commonly caused by worn top or bottom end parts. If you find that you're engine is displaying signs of worn piston rings, valve train components, or bearings, your first thought may be, "how much is this going to cost me?" Luckily, expensive, premium aftermarket brands and overpriced OEM parts are not your only option. For example, ProX Racing Parts has a catalog full of OEM-quality replacement parts, many of them made by OEM manufacturers, but priced more desirably. Depending on what you need to replace, affordable engine parts like piston kits, valves, cam chains, connecting rods, bearings, and gaskets can be found in the ProX catalog.
Stay attentive for these signs of possible engine wear. It's always better to replace parts as preventative maintenance practice, and not because you're trying to fix something that is no longer functioning.
Don't give up OEM+ quality just to save a few bucks. Get the best of both worlds and find everything you need for your bike at Pro-X.com.
 
It's always better to err on the side of caution when deciding if your engine parts are worn enough to replace yet. ProX parts are a great option for staying within budget while retaining OEM quality.
A couple other key points to keep in mind: discussing specific time intervals in regards to when things should be replaced is futile. The reason is simple: different engines, maintenance practices, and applications will all have different intervals. Installing an hour meter on your engine so that you can log the number of hours the engine has run can be one of the most insightful ways to establish maintenance and replacement intervals specific to your engine, riding, and maintenance habits.
ProX Hour Meter

 
 
 
 

Hello there, 
Recently I noticed that my chain is rattling a bit around the front sprocket when I accelerate. I adjusted the chain slack to specs and lubed the chain and it got somewhat better but there's still a bit of a noise left. 
I've been doing a good amount of work on the bike myself and I'm open to replace the chain and sprockets, but I don't want to if I don't have to. I can tell that the chain is no longer rounded and it's flat on the sides which is not a good sign but not sure about the sprockets.
Can someone with a trained eye give me an idea based on the pictures if they definitely have to go or if they've got a decent amount of life left on them? 
Thank you!

Chances are if you ride dirt bikes, ATVs, or operate any other wheeled powersports machine, you will eventually have to bleed your brakes. Brake bleeding in itself is not a difficult job, but there are a handful of tips and tricks that can make the process go more smoothly and result in better performing brakes.
Servicing brake systems by replacing worn components as needed and refreshing the brake fluid periodically is a critical maintenance task that is often overlooked. In this article, we’ll provide an overview of the brake bleeding process and share some tips that can make the job easier. We’ll even provide a few pointers that can make rebuilding your master cylinder go more smoothly.
From pads and rotors to master cylinder and caliper rebuild kits, check out ProX braking components here.

Bleeding brakes is not only necessary when there's air in the line, it's also a normal maintenance task that should be performed periodically.
The necessity to bleed your brakes may crop up for several reasons. The tell-tale signs that your brakes may need to be bled are reduced braking power, inconsistent braking, and sponginess felt in the lever. If any of these symptoms exist, it is always a good idea to check the integrity of the system. Leaks can occur as a result of loose banjo bolts, damaged seals, and cracked lines.
 
If you're feeling sponginess in the lever or less braking power, be sure to check your brake lines and banjo bolts for damage and leaks.
 
To start, it is always a good idea to consult your make and model’s factory service manual for information specific to the task at hand. Within your service manual, you’ll find torque specs, detailed procedures, and fluid information that can be important to take into consideration when performing the job.
Unfortunately, brake fluid is a harsh chemical and should be treated as such. Both you and your machine can be adversely affected by inadvertent contact with brake fluid. When servicing your brakes and bleeding your lines, be sure to take any necessary precautions and avoid skin and eye contact. Wear rubber gloves and safety glasses when bleeding the brakes. If the brake lever is pump too quickly during the bleeding process fluid can be shot into the air from the reservoir. Brake fluid can strip paint and cloud plastics, so be sure to protect your machine’s surfaces with a towel or rags to limit exposure.

Brake fluid is a very harsh chemical, be sure to protect yourself and your machine.
 
Brake fluids used in automotive/powersports applications within the United States and many other parts of the world are divided into three classes. Specifications for the classes are outlined by the Department of Transportation (DOT). The commonly available fluid class options are DOT 3, DOT 4, and DOT 5.1. The majority of powersports applications utilize DOT 4 brake fluid. Usually, your machine’s brake fluid reservoir cover/cap on the front and rear master cylinder denotes which fluid is used. In general, mixing of brake fluid classes is not recommended because of compatibility reasons and differences in boiling point.

The correct type of brake fluid for your machine should be noted both in your owner's manual and on the master cylinder cap. Do not use anything other than the recommended type.
 
Prepare to bleed your brakes by positioning the front or rear master cylinder and reservoir as close to level as possible. When working on the front brakes, this often means turning the handlebars to one side or the other to achieve a level reservoir. Don’t forget to position towels or rags around the reservoir in case of a spill.

Make sure your master cylinder is as level as possible to avoid spilling fluid. Wrap a rag around the master cylinder in case of an accident.
 
Once situated, remove the reservoir cover or cap, depending on which system you’re working on. Reservoir cover screws can be prone to stripping, so proceed cautiously. Typically, flat head Japanese Industrial Standard (JIS) screws are used on Japanese equipment. While a Phillips bit is close in profile, it is not the right bit for the job and will more easily strip the fastener. Pick up a set of JIS screwdrivers or bits; otherwise, the tip of a Phillips bit can be ground down in a pinch so that the bit fits the JIS profile more closely.

After the cover or cap has been removed, proceed to remove the diaphragm. The diaphragm may come off with the cap, so be careful not to drop or damage it.
 
Transition to the caliper and remove any necessary covers or guards so that the bleeder valve is visible. The bleeder valve has a rubber cover that protects its flared nipple and should be easily identifiable. Size a clear piece of tubing so that it fits snuggly over the bleeder valve nipple and has at least six inches of length, or enough length to drain into a catch bottle.
 
Remove the protective rubber cap from the bleeder valve and place a piece of clear, plastic tubing over it. Make sure it's snug and completely covering the flared end. The other end of the tubing should be placed into a catch bottle.
 
To begin the bleeding process, squeeze the brake lever (front) or push the pedal down (rear), then open the bleed valve ¼ - ½ turn. A mixture of air and brake fluid should exit from the bleeder valve and be visible in the clear tube. Close the bleed valve. Next, slowly release the brake lever or pedal and allow it to remain at its original extended position for a few seconds before repeating the process.

Squeeze the brake lever (front), then loosen the bleeder valve approximately 1/4 turn. Once the lever compresses all the way in to the grip, close the bleed valve, then release the lever. Repeat this process as necessary to work fluid/air out of the system.
Keep a close eye on fluid levels in the reservoir. If all the fluid in the reservoir is consumed and air is sucked in, the whole process will need to be restarted. Add fresh brake fluid to the reservoir as necessary throughout the bleeding process to ensure no air ever gets sucked into the system. When adding brake fluid, be very careful to ensure no contaminants such as dust or debris enter the reservoir. Any small particles that find their way into the brake system can cause the system to malfunction or prematurely wear.
Time to replace your brake pads or rotors too? Find quality, affordable brake components here.

Keep the fluid level in the master cylinder high enough to avoid sucking air throughout the bleeding process. Using a plastic syringe is a great way to avoid spilling fluid when filling.
The bleeding procedure outlined should be repeated until the mixture exiting the bleeder nipple consists entirely of brake fluid. This may take a short or long period of time depending on where and how much air is in the system. Once the brakes have been properly bled, a noticeable improvement in the feel of the brake lever or pedal should be felt when the brakes are actuated.

Keep an eye on the clear tubing and bleed until there is nothing but clean brake fluid with no air bubbles exiting the bleed valve.
 
Upon completion of bleeding the brakes, ensure the fluid level in the reservoir is at the upper level of the fill line. Then, carefully install the diaphragm, cover/cap, and any other remaining hardware. Be sure to double check that the bleeder valve is tight. Once the machine has been reassembled, test the brakes one final time by rolling the machine forward and backward and noting how responsive the brakes are. Assuming everything checks out, the machine should be test ridden.

Once everything is put back together and re-tightened, test the brakes in the garage by just rolling the bike back and forth to make sure they are working properly before riding it.
Perform a test ride by progressively increasing the machines speed and brake load. Do this based on brake performance and as you gain confidence in the brake system. Always pick a suitable test location and be sure to leave yourself ample room in case something goes amiss. Before performing high speed and load braking tests, stop the machine and check over the caliper, line, and master cylinder to ensure there are no leaks.
Master Cylinder Tips
If you continue to encounter problems with your brake system after bleeding or find worn out components in your master cylinder, it’s time to rebuild. Master cylinder rebuild kits make it easy and affordable to get your brakes performing again. The aftermarket is a good source for affordable rebuild kits for a job like this. ProX Racing Parts offers affordable master cylinder rebuild kits that contain OEM-quality parts, complete with all pieces necessary for a standard rebuild. Here’s a few tips to keep in mind during a master cylinder rebuild to ensure your job goes as smoothly as possible.
 Be sure to use a snap ring plier when removing the snap ring from the master cylinder. Attempting to extract the snap ring with anything else often leads to damaging the snap ring groove and surrounding geometry.
   Once the master cylinder has been completely disassembled, be sure to clean the entire master cylinder before reassembly. When cleaning the master cylinder, only use brake fluid.
   Check the master piston and cylinder bore for abnormal scratches. If deep scratches are present, the piston and cylinder should be replaced. Also, reference your service manual for any applicable inspection measurements that should be taken.
   Upon reassembly, be sure to apply new brake fluid to the master piston and master cylinder bore.
   When installing the boot, be sure that it fully seats.
Should you encounter leaks or operational issues with your brake caliper, calipers can also be rebuilt and resealed. ProX offers caliper rebuild kits complete with new rubber boots, seals, bleeder caps, and retaining pins. All ProX components supplied in master cylinder and caliper rebuild kits are designed to OEM specifications to help ensure to the same longevity your machine’s brake system had when it was new.

Should your brake caliper be leaking internally, caliper rebuild kits are also available to save money over buying a new caliper. Find caliper rebuild kits for your machine HERE.
 

Hey guys,
About 1.5 years ago, I rebuilt my 650 engine and installed a 100.5mm Pro-X piston, with the cylinder rebored accordingly. Everything seemed fine until a couple of weeks ago when I noticed my bike started producing blue smoke. I initially thought it might be the valve seals, even though I used brand-new OEM ones.
After a recent trip, I found that my oil levels had dropped significantly, going from around 2L to just under 1L, which was a big red flag for excessive oil consumption.
I decided to open up the top end, only to find the piston wobbling side-to-side, with clear wear in the bore. I was shocked since I followed the manual meticulously, using all the correct measurements. After removing the cylinder, I discovered the piston pin had chewed up the inner sides of the pin bores badly.
Upon further inspection, I realized that the Pro-X piston lacks pin-bore lubrication holes—something OEM pistons have. It looks like this missing feature caused serious damage: overheating, metal-on-metal grinding, and overall destruction of the connecting rod bore and cylinder face.
So now, I’m left wondering how this piston pin was supposed to get any lubrication in those bores. Do other brands, like WISECO, have similar issues, or do they include these lubrication holes?
Here’s what I’m weighing:
Connecting Rod: Replace the aftermarket Pro-X with an OEM one or stick with the Pro-X if it’s actually reliable.
Piston Choice: Considering a WISECO 101mm or going with a 100mm sleeve and OEM piston. But I’m wary of facing the same problem I did with the Pro-X if the WISECO doesn’t have those crucial lubrication holes.
I’d love to hear your thoughts on this, especially if you’ve used WISECO pistons or have had a similar experience. I’ve attached some photos to give you a better look at the damage.
Thanks, everyone!

The infamous crf casing tab for front cam chain guide.. 
It's an 05 450r, the cam sprocket fell off, the bolts were loose and had sheared.. made a right mess but a lucky escape for the engine. 
Here's my quick fix for the said scenario.
Fairly red neck but it will do the job..