YM 336D RPMS go up and down at higher speed

[R Barger]

When the rpms are above 2000 the engine speed goes up and down. Any Idea's?

 

[winston1]

Any slack in throttle linkage? Make sure outer throttle lever is not moving.

Weak governor spring?

 

[Soundguy]

it's either a bad governor.. or linkage with slack or preload.. or there is a fuel obstruction.

does it do the 'hunting' under load, or unloaded.. or both?

 

[R Barger]

I have the front axle tore down replacing bearings and seals so unable to check in under a load. with no load it's not real bad just not steady. I just thought there might be an adjustment I could do. It's going to be down a while because I have to order more parts.[ Lesson learned never buy 4wd without checking front axle.]

 

[normde2001]

You can check governor adjustment. Gov. wide open, throttle wide open, nail it. Obviously, parts free and proper spring tension. Not, by chance, runnig without air filter? As said, either governor, or lean fuel/air mixture.

 

[R Barger]

Haven't replaced fuel filter yet. Yes it has a air filter and I will check throttle linkage when I get off work this afternoon. Thanks for the suggestons

 

[Pete Judd]

Sounds like a fuel or air filter issue to me as well.

 

[R Barger]

I changed the fuel filter and it didn't change anything. It's about a 100 rpm rise and drop when above 2000 rpm's. At 1500 rpm's it's fine. Still haven't got the front end back together to see if it does it under a load. Hopefully by the weekend. It seems more like a governor issue.