YM2000 revs uncontrollably

[yanmardoug]

New to me YM2000. Was running ok, but some white smoke. Pulled the head. No observable problems. No gouging, scratches, or lands in the cylinders. Poured deisel in the cylinders. One held overnight, the other drained into the pan within 20 minutes or so. Reinstalled the head and changed the oil.. Got it started by pulling it and it ran fine for a minute or two before revving to high rpm. Took several seconds after closing the throttle before it finally idled back and died. Haven't been brave enough to try it again. Any ideas as to what is going on here?

 

[winston1]

Injector rack sticking?

 

[California]

Could it be self-fueling from oil or diesel spilled in the manifold, or oil getting past the rings?

 

[Pete Judd]

I have seen the old 2 stroke Detroit diesels, do that when one jug losses compression and the crank case oil gets sucked in. That's why they have a flap under the blower that you can flop down to shut down the air.

 

[California]

I was thinking of approximately the same thing. Somebody posted that working construction, he had seen old worn out diesels in forklifts etc self destruct if the unit got flopped on its side. Oil coming up past the rings fueled the engine same as full throttle and there was no way to shut it off as it over-revved.

 

[yanmardoug]

Thanks all for your thoughts. I was afraid that it was burning engine oil coming up past the rings in the cylinder which drained fuel quickly. Guess I'll have to pull the pistons out and check the rings though I can't really figure out how the engine could be getting lubricating oil into the combustion chamber in sufficient quantity to run the engine at full throttle and still have enough compression to ignite the oil.

 

[Domush]

Have you checked for the more basic issues, like throttle sticking? You be kind of red faced if it was just the foot throttle getting jammed a bit.

 

[yanmardoug]

Domush,
Being more familiar with the YM1500, which has no foot throttle; the possibility that the foot throttle might be overiding the throttle lever did not occur to me. Thanks for the suggestion; I'll check that out. Though I never used the foot throttle, I do now recall that there was some kind of issue with the foot/lever throttle operation. Therefore, an idea well worth considering.

 

[Neat 1500]

Injector rack sticking?

i would look at this properly as this is what it sounds like. the spring may have broken.

 

[clemsonfor]

Im thinking injector pump as well. The Hand throttle and foot throttle are connected. If the foot petal is depressed i think the lever is weded open as well, may be wrong on this as mine functions correctly, but when i pull the hand throttle open the foot depresses and then the reverse to slow it.