Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126288
; . IIIlI ~ ,:. ( t 1" 1" 0') 1"""'4 ~ IN ~ ~ ..0 e ~ ;> 0 Z (Abovel Pencil points to one of the wrist-pin retaining circlips. Fit new ones every time you remove them. (Left) Cleaned. inspected, ready to reassemble. (Bottoml Go easy with the hone. (Belowl Hand Cleaning tools. WORKS By Dave "Works" Miller and Jack Wright Weekly top-end maintenance To have a motor that will pe r form to its maximum potential, last longer, and run the same week after week takes some effort 12 on your pa rt as the rider/mechanic. It won't sta y together by itself. The topend should be tom down , inspected and cleaned every week , to remain competitive on any level of racing. That is, if you are ra cing seriously . The time in volved is not much compared to the added assurance of keeping your motor from selfdestructing between your legs while you are leading your moto. If you ha ve access to a glass beader, solve nt tank , and hone the whole procedure won't take more th an one hou r of you r ti me, once you are acquainted with it . If you do n't have these tools ava ilable (not many peopl e hav e a glass beader in their garage), it ma y take awhile longer. In that case you will need a scotch brite pad, which is a nylon briIlo pad with out the soap , a sta inless steel wire brush available from an y weld ing supply store for about 75~ . em ery cloth. contact cleaner, and solvent . If you are not experienced at honing cylinders we recommend that you take it to your loca l bike shop to have this done. It 's best to wash your bike before loosening any bol ts. You don't want dirt or anything else that you might have collected during.your last race to fall into the motor and cause more problems than you might already have. Pull the head off. If you . haven't done this for awhile, or ever for that matter, you will probably discover a rather large buildup of carbon on it. If you don't have a glass beader, use the contact cleaner to soften the carbon and the wire brush and scotch brite pad to remove it. Be sure to remove all the carbon, leaving the combustion chamber completely clean. Wash the head with solvent , paying special attention to the spark plug threads . If there is any dirt or carbon left in the threads you might tear them up when you replace the spark plug. To reduce carbon buildup on the head in the future and allow better heat transfer (which is essential for engine cooling), polish the combustion chamber with emery cloth. After using the emery cloth, use a po lishing compound to polish the aluminum until it starts to shine like chrome. Next remove the cylinder. If you have a reed valve , take it off so that it won 't get gummed up when you decarbon the cylinder. Clean all the carbon out of the exhaust port using contact cleaner and a scotch brite pad. Polish it if you can. This will allow you to just wipe it clean after the next race. The exhaust flange should also be cleaned and pol ished . When the steel gets hot , unlike aluminum, the carbon really builds up and sticks. Polishing it will build up a res istance on the surface of the flange. As we 'said earlier, if you have never done honing, it's better to take your cylinder to your local shop to ha ve it done . There shouldn't be an y problems with the hon e catching in the ports if someone with experience does the hon ing. You want to make a couple of passes th rough the cylinder, just enough to break the glaze on the cylinder walls. The ring of carbon between th e top ring and the top of th e cylinder can be removed with the scotch brite pad and contact clea ner. Is it worn out7 The piston should now be removed and inspected for wear. To check for looseness of the piston in th e cylinder, look to see how far down the carbon goes on th e piston . If th e carbon is just below the ring, or below the lower ring on a dual ringed piston, that's normal because the piston is tapered with the smaller diameter at th e top . If the carbon is halfwa y down the side of the piston you can be sure that it is worn out. You also want to check and see if di rt ha s been run th rough the motor, causing wear. Little particles of dirt will put tiny lines or groo ves in the side of th e piston making it appear flat grey looking . This is also a good