My 02 Yz 250 two stroke wont rev up past half throttle, it bangs out. The CDI box is new and the TPS sensor checks good, carb is clean and everything is working properly what else should i try please help
Check the compression. It should have at least 100 psi,..if not,then its time to rebuild the top end..IE piston,rings,bore cylinder. If compression checks out,i would start with the power valve. Two stroke dirtbikes power valves are notorius for gumming up and sticking,causing them to not rev correctly.
SOURCE: MY YZ250 WONT REV PAST 3/8 THROTTLE. I NEED HELP!!
It does sound like an ignition timing problem, but could also be a breathing issue, air flow in or exhaust flow out could be restricted i.e.:dirty air filter, excessive carbon build up in exhaust pipe from burning too much oil or rich fuel mixture.
possibly and more likely some junk got into your fuel system and partially plugged up the main jet in the carb, -or has the needle on the slide been moved? The little circlip at the top of the needle, if it has one.
1.Replace the spark plug, check gap, check spark, it should be bright blue and fat.
2. check the fuel filter, if no filter check the carb for dirt.
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