This is for all foam air filters. Ok , this might be a boring subject, but it is a very important one. It amazes me the number of bikes that are brought into my shop with this one complaint " it feels down on power, I recently replaced the topend . What could be wrong ? " First a quick compression check, sometimes all you have to do is lay a finger on the kickstarter and it will fall down. Off come the seat and out with the air filter. And there it is -- a layer of dust inside the air boot. It only takes a little of this dust to get by and the rings or worse are wiped out. Think about this -- most 125's peak out at around 11,000 RPM ( revolutions per minute) so let's see , this piston is going up and down 11,000 times a minute . WOW , that is 183 times a second. Now lets mix in the dust / dirt going past the piston and rings, not to mention the crank. It is kind of like an orbital sander going to town in there. So how do we avoid this? Lets assume the air filter is dirty and not a new one. If you have used a petroleum based oil like bel-ray air filter oil you should start with a solvent based cleaner , something like Safety Klean or kerosene. Make sure you USE rubber gloves that are solvent proof and are working in a well ventilated area . Wash the filter in this one or two times and try to wash the filter from the inside out . This will push the oil and dirt out of the filter instead of thru it were sometimes small grains of sand will get stuck and are almost impossible to bet out (this is a time bomb waiting to get pulled thru the air filter and wreak damage on your engine). Next wash the filter in some warm water and some fairly strong liquid/powdered detergent. and finish with a final rinse of water only .The soap will remove the lighter based oil were as the solvent will thin out the thicker air filter oil and remove most of the dirt and oil. You should do both steps. If you only use the solvent --- the filter will not properly dry. So when you reapply the new air filter oil it will thin it out and make it less tacky. Now that the air filter has been cleaned with both steps let it completely dry. Now apply the new oil . you will only need 2-3 ounces of oil to properly oil the filter . This should be worked completely through the filter and have an even appearance any area's not covered with oil should be treated. I like to do this by putting the area that needs to be spot treated on top of the bottle and blot the filter with the oil . Then work it through. It is also a good idea to let the filters for a good 15-20 minutes before reinstalling it into the bike. Many of the oils have a product in it that will evaporate after the oil is applies . This allows the oil to be thinner right when applied and lets it work in easier and then it will evaporate and get thicker/ tackier . Some people use a little grease on the rim of the filter. I personally do not use any.The rim is treated with the same oil as the rest of the filter. And have not had any problems in 27 years of riding. If you tighten the air filter down properly and the rim is seated good -- you won't have a problem here . Now if you use the no - toil air filter oil and cleaner you do not have to use the solvent (their oil is not petroleum based). You just use their cleaner with the water , a good complete dry down and go from their. Also you do not have to worry about all the toxic chemicals and the fire / explosion danger. Also take the time to use a flash light and look down into the air filter boot to make sure their is not ANY specs of dirt in their. You should be able to eat off of it. The same goes for the air filter cage. Also clean the air filter box. This should be done on a regular basis also. As for the guy with the engine problem . We will have to do a complete tear down and inspect the engine and clean the carb. and reeds. There are a lot of bad places for that dirt to get into , and we don't want to do that --- do we !!!