I have a old but in really nice shape 1980 Yamaha MX175. It's the white off road only version of the Yamaha DT line. I have a problem with it, that's driving me crazy. It quit running and I couldn't get it restarted. I was getting eradic spark so I changed the coil and spark plugs wire, still eradic, changed the CDI and I looked into the flywheel which I found out was the wrong flywheel, but this bike was running good on it, it was not tight and slipped off, no puller needed. I replaced it with the correct flywheel. Good blue spark, still won't start. Tore the top end off. Had compression but the rings were definitely worn, the Piston had a small chunk out on the exhaust side so I chucked it. But a Wiseco kit and rebuilt the top end. Honed the cylinder, like new. No grooves, no gouges. Nice, standard bore. All new gaskets, put it together. Still won't start, nice blue spark. Lots of compression. Tore the carb apart, nice and clean, the pilot jet was dirty but not that crazy. It's getting fuel. Only thing left is it's out of time. Guess I ll pull the flywheel and check the stator plate to see if it came loose and turned but I am about out of things to look at. Driving me crazy now. Anything else to look at. I am a two stroke guy but this bike has be ready to part it out. I have a Old 1980 DT175 that I still have plates on. I bought this bike for parts but it actually ran better than the DT so I just rode it off road as a fun bike then it just stopped and wouldn't start. These are pretty simple durable machines. Truly the Apocalypse bikes or so I thought.