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You are right on with your air leak assumption. Get yourself a pressure testing kit (aka leak tester) for a two cycle motor and put it to use. If it gets substantially worse when warm, that makes me think it might be in the sealing surface between the engine cases that could be expanding to leak more when heated. If the leak is in the crank seals, be sure to inspect the main bearings too. Too much slop in the bearings can cause the seals to leak, and is the only drive line connection I could see being related to your clutch actuation symptom.

Good luck,
Jon

Author:	STRAT21 [ Wed Jul 28, 2010 8:09 pm ]
Post subject:	Yamaha MX 100 Problem
Hi, I am having problems with my 1981 mx 100, I have done everything tweeked the carb/ cleaned the carb, new gaskets, made sure that everything close to the engine is air tight as possible. Whenever I start the bike it idles fine but if I go down the road or ride on one of my trails i can pull in the clutch because if I do the engine revs ungodly high and when it does I have to put it in gear and then hit the killswitch to kill it because it will not kill even when I hit the killswitch. I dont know if I have a air leak or what but I need somebodys help with this cause id like to use my clutch. Thanks, Clay

Author:	mrmikkelsen [ Mon Aug 02, 2010 9:08 am ]
Post subject:	Re: Yamaha MX 100 Problem
You are right on with your air leak assumption. Get yourself a pressure testing kit (aka leak tester) for a two cycle motor and put it to use. If it gets substantially worse when warm, that makes me think it might be in the sealing surface between the engine cases that could be expanding to leak more when heated. If the leak is in the crank seals, be sure to inspect the main bearings too. Too much slop in the bearings can cause the seals to leak, and is the only drive line connection I could see being related to your clutch actuation symptom. Good luck, Jon

Author:	STRAT21 [ Mon Aug 16, 2010 9:15 pm ]
Post subject:	Re: Yamaha MX 100 Problem
I finally figured it out, it was the spring inside the carb which was getting stuck which caused it to rev to high whenever you pull in the clutch. Thanks for the advice I really appreciated it! Clay mrmikkelsen wrote: You are right on with your air leak assumption. Get yourself a pressure testing kit (aka leak tester) for a two cycle motor and put it to use. If it gets substantially worse when warm, that makes me think it might be in the sealing surface between the engine cases that could be expanding to leak more when heated. If the leak is in the crank seals, be sure to inspect the main bearings too. Too much slop in the bearings can cause the seals to leak, and is the only drive line connection I could see being related to your clutch actuation symptom. Good luck, Jon

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