1995 250 Yamaha lossing 300 RPM at high speed

[Chas1776]

I have twin 1995 250 Yamahas that use to run at 5200 RPM, now from idle to 4800 RPM they run in sync, as I advance the throttles the starboard engine RPM doesn't want to increase in RPM, If I trim up the motor it will increase as cavitation starts. I just had the carbs rebuilt hoping that would help, change the plugs, the motor was rebuilt 88 hrs ago and new fuel pumps were installed. What else should I look at? is it a fuel issue or a stator problem?<br />Thanks, Chas.

 

[rodbolt]

Re: 1995 250 Yamaha lossing 300 RPM at high speed

hello<br /> time to test everything. you can try running with the airbox off and spray a bit of premix in each carb throat. its time for a complete evaluation. also test the spark plug caps with an ohm meter<br /> a faulty T-stat can even cause power loss. as can a bad enrichment valve or a bad fuel pump. those 3.1 motors are hard on them.