Tweet
Engine idles fine but missfires and stumbles when attempting high speed.
-
-
rac,
Sounds like high speed jets of carbs are plugged up. If it has been at least three years since last carb overhaul or if the motor was allowed to set up for at least two months w/o being run, you might consider a teardown, cleaning, and carb kit install.
Or you might try just removing the high speed jets and squirting some Berryman's Chemtool into the orifices - any distorted or cracked o-rings on the ends of the jets need to be replaced.
Or you could have fuel pump problem. When you attempt high speed, have someone pump the fuel primer bulb fast and hard - if the motor runs at high speed, albeit for a short period, then I would suspect a bad fuel pump.
Also, make sure all fuel filters are clean and have no restriction.
Get yourself a Yamaha shop manual to guide you along.
Good luck [img]smile.gif[/img] ,
Ken K
Comment