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
. in d ication that your piston sho uld be replaced. If you can see whe re the piston has been rubbing against the bore , but is still shiny and has machined marks, most likely it is still in Rood condition. Check the manufacture's specifica tions for how many races you can run on the piston. Then decide whether or not you should replace it. To decarbon the top of the piston (if a glass beader is not available), use the wire brush and contact cleaner. After the top of the piston is clean , it is im po rt a nt that you clean all the carbon out of the ring grooves. That way the ring will float in the groove, according to the tension it has on th e sides of the cylinder, but won 't bind up and form a poor seal. With the grooves clean the rings form a much better seal because they are free to move. The best way to clean the ring grooves if you don't have a glass beader is to break an old ring in half and drag it through the groove. Using contact cleaner to soften the "arbon, scrape the carbon out of the slot, being ca reful not to gouge the piston. Be su re to keep the ring in line. If you start pulling towards the top or bottom of the piston you will start to remove metal. If this happens it will cause the ring to flutter and chatter on the bore, forming a poor seal. Do not use sa ndpaper. Using sandpaper will immediately start removing metal . causing the same bad results. For single ringed bikes we replace the ring every week, and double ringed motors every three weeks . for maximum performance. Check your m a nu fact ure's specifications for ring wear and end gap according to the make and model. 1 If your cylinder has a reed valve, inspect the reeds for breakage. Make sure the ends are not chipped or !=racked . If they are, replace them . Be sure to clean them thoroughly and use jl silicone sealant when reinstalling them in the cylinder so there will not be any air leaks. i The wrist pin and wrist pin bearing. along with the circlips, are an area that tends to get overlooked. To inspect the wrist p in run you r fingernail down the length of it checking for high or low spots. If there is evidence of either. replace it. Most all wrist pins that have been run will have heat marks on them . If the wrist pin is p urple and blue all the wa y to the edges, also replace it. We change wrist pins every eight races . When inspecting the wri st pin bearing for wear, what you want to check is the edges where it rubs th e piston. If they are moderately shiny replace it. If the bearing is excessively shiny replace it and check the rod for wear . With the circlips it's better to replace them rather than take a chance of having them break because 'they have worn out. Circlips are one of the least expensive items on you r 'motorcycle. Replace them rather than have them break and destroy your motor. . , If youhave copper head gasket and if it is still in good condition you can use it over again . Heat it up over the stove unt il it starts turning a blue co lor and drop it in cold water. Heating the co pper causes it to expand. returning it to its original shape. You can probably use it 10 times this way . Always replace the base gasket. Again the cost is minimal compared to the worth . Tearing the top -end of your motor down once a week takes effort. It takes someone with a real desire to win to do it. Paying $13-$15 on gate and entry fees on ly to be passed by another guy on a stock bike or even DNF can make you wish that you had put in that extra hour during the week . • a GLIE strength rx. A study in IfyOll ride mofoC/~ hare design make for a sfiffer and ~(jamh~ or endllrrx, we.'re not harder working abouffo fe/Iyou hoW ptJni~hing /fcan be. Bl/fwe wouldlike. fo fell you Ihis Goodyearha!" :... ~flldied mofocro.r~forsomelime ana; wiTh fhe help of nders like AMA /Q7S~Clpercr~ Champion Jimmy Weinert; we engineered anew MI Xlire. The Eagle M/XI!. YOll ~hotlldknow what we d/a; and why we dtd if. 1.. The Eagle.MlxII sfarfr wifh a rllgged nylon cord bod~' fhen a 17eJA.1 i exfremeJyfear-- l] fire. ~l7allow grool/~ in the top ofeach lug ptlfhundteds ofbiting edgesto work when yOUle. running on marbly hard osc« ~urfaces. I-< o Z or 3. The EagleMlxII ha~a neu/ high-sianding£idewalt de9gned To flex andeosoro fhe kind of wock a motocross can fhtOw afyo{/. 4:The. M/XIL.. .1ft a Goodyear Eagle. And every Eagle fire/!: pain~iaking/y enq/neeeafor a¥Jecihc fype ofddet: Thetek one forfhe uey YOt! ride, A~k n ~-~:..._ oercomooana yourfnend~ I rws-fanfrub- kkyour Gaxiyeardealer C1bouffhe Bigle ! i~added. 0<') C'I . M/XII... itk a ~fudy in ~ftel7gfh. 2.lf~wlde, flaffootprinfandfait fapered/tlg GOOD/yEAR II you must go laster, think lirst how you'll look in plaster. HUSQVARNA CLEARANCE SALE 75, '16, 77 models must go im m ediat ely to make room for '78 models. Prices reduced to sell fast while they last, Any reasonable offer accepted. T&OYamaha 24020 Narbonne Ave. Lomita, CA 90717 213-534-2311 (T o r ra n c e-Re d o n d o area) TERR l -C~4HL~' The Teflon Super Smooth Cable I would like to address this me.sage to the riders end d••Ie,. of the ' oRowing bnlnds. SUZUKI: The 2 new models of RM 250'1 8JtI the finest Suzuki$. ever made and are probabtv the bn1 2 stroke racers in the WOfkS today. HON DA: You Honda people have comp!a;ned for years about not having a racer • well. the CR 250', are great * Complete line for racing bikes *Requires no o iling *Smoothest pulling cable *Flexib le t hrottle w ire gives lo ng life *Heavy duty housing, resists stretch and abuse Write for F ree literature Terrycable PO Box 1321, Hesperia. CA 92345 (714) 247·2646 Out of state call toll free (80018544691 and they are din cheap - there are thousands of used ones around , if you cannot afford a new QI'le . CAN AM: This is the most powerful 250 engine going. They are the result of yean of power development and are ma de right next door. KAW ASAKI: The KX 250 Kawasak i has the large5t transfer port area of the new generation of bikes and has 8 tremendous potential as a win","" I d id not me nt ion Yamaha, Harley Dav idson , Buttaco or Ossa becau se we already know they Me pro ven winners. Any of these 8 engines ere ready and willi ng to w in 8 Nat ional Champ ionshi p, Wh at lam tryi ng to say is - let 's get to w ork , I for one am tired at seeing 1 Of 2 brands wi n every time . aren't vou? II I leh ou l your brand , don 't despai r, ther e are 4 more ju sl as good as thos e noted . • •It& • • • • 2415 Brown Rd., SI. Louis, Mo . 63114 Phone 314/426-6959 or call Charley Chapple 3131735-5453 13