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Vintage Yamaha experts please - 1982 YZ100j piston question

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I have said bike and the 1976 piston looks almost identical short of the location of the side hole. Is there compatibility there or any other year pistons? I've been looking all over and there isn't a lot of info. I need rings and a piston for my bike. Many Thanks!!



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go to EBay and find rings for the same cylinder bore and ask the seller what the thickness of the rings are. Buy them if they match yours.

Important points for the used/abused piston is that the edge that the ring rests on is flat (so the seal is good) and that there isn't any piston slap. What is the clearance between piston skirt and cylinder?

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I bought the bike yesterday. It is missing the carb throat slider and I can't find one. It appears to be 33mm so I'm hoping for some crossover parts from something since its mikuni. Here are some pics of what i am working with. 










I paid $125 for the bike so I'm happy with the project. The tires were worth it alone. Amazingly the cylinder bore is smooth and good to go.  The rest of the bike is in pretty good shape for a 35 year old bike. I havent had a two stroke in a few years so adding to the pile will make for a fun addition. I'm very impressed with the big bore piggy back cantilevered rear mono shock and air valve front shocks on a 1982 model. It must have been a legend of a beast back then. Best i can tell a head swap would turn it into any size you wanted at the time.






I do actually have the rear side plastics for it as well. Look like new. Quite amazing considering I've bought 8 bikes last year and only one has plastics. Lol. 

Edited by One1

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