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Hi all,

I have a 1978 Yamaha DT175 and I can't seem to get rid of a misfire at approximately 3500 to 5000 RPM. The engine idles fine and when opening the throttle, it accelerates without a problem to redline. It's when crusing at the above RPM that the engine misfires.

Could be a spark plug problem.
Check its condition or probably use a new one and see what happens first.

Not much to the electrical system on those stator with excitor coil and lighting coil. CDI and regulartor, rectifier. Coil and spark plug. If not check your reed valves. Then check the carb and clean it GOOD.