I have a YS 91 AC has about 3 gallons ran through it. the problem i'm having is the motor will run with the high speed needle valve closed tight. it runs perfect at this setting if I open it up an 1/8 turn it runs rich and if I leave the regulator flush it still runs rich with the high speed needle valve closed I have to tighten up the regulator turn the regulator to about 1/2 to 1/3 way in before it will run well even with the needle valve closed I have checked the valves the intake valve was way out of whack and when we set it I notest that now that I am at the end of the threads on the intake side we took out both rods and they are the same length also replaced the diapfram and plunger and every thing else in there

any one know what is causing this problem

There could be a couple of things going on here.

On the valves: If you are running out of adjustment, the pushrods are likely worn and need to be replaced.

Does the needle valve bottom out on the needle socket? If it does, the needle assembly is worn out and needs replacement. This is a problem we usually only see in engines with a lot of running time.

Both of these problems sound like the engine has a lot more than three gallons of fuel through it. 91 AC's haven't been made in about 3 years. Did you buy this engine new? When?

Dave Shadel

I was running out of adjustment but only on the intake we took both rods out they looked the same in lenght the needle valve dose not bottom out on the socket I bought this motor new a while back but never ran it I still have one more new in box that I have not ran what would it cost to send it in and have it fixed

Thanks Tim

It's almost impossible to say what it will cost to do these engines, but since they are nearly new it shouldn't be too bad. An estimate is free if you just send them in and request it. You can then decide what you want to do.

The service dept. address is:

YS Service
1295 Industrial Court
Gardnerville, NV 89410

Phone 775-782-4562

Good Flying,

Dave Shadel