90 hp 2 stroke idles fine but boggs down when throttled up

[mcclaine]

engine has been running fine until this past weekend. engine will run all day smoothly at 1200 rpms. when i attempt to accelerate it has no power. if i throttle down to 12-1500 rpms it runs fine no alarms. i am thinking it may be the fuel pump but wonder why it will run fine at low rpm. any ideas? fuel is fresh, new plugs, new fuel filter

[ausnoelm]

make sure the timing is advancing as the throttle is applied, easy to do and is fairly common, and causes the problem you describe. Just remove the engine cowling (with motor not running) and have someone move the throttle while you watch the motor end, ensure the carby part moves along with the timing assy that is under the flywheel, it is connected by a linkage and is easy to see. If all that is OK, then I would be suspecting a carb rebuild is in your near future.

[mcclaine]

Wanted to thank you for your response. had to go out of town and have not been able to try your advice. will let you know thanks.

[Randy Douglas]

I have a yamaha 60 2 stroke with CDI. When I move the throttle past idle the engine quits. If I move the throttle lever physically it works fine. What could be the problem. PS new CDI unit, cleaned carbs, new plugs.