R Verbael

I have a used YS F-120 installed on a 4 Star 120 and cannot figure out how to set the high and low mixtures. It now runs very rich at the idle end and appears to be lean at the high end of the RPM range. How do I go about setting this engine up. There does not appear to be any low needle valve to set the low end. I did not get any paperwork or instructions with the engine.

Thanks for any advice.

Russ Verbael

krayzc-RCU

My Feedback: (31)

the older ys 120 does not have a low end only a high needle........

w8ye

My Feedback: (16)

There may be something wrong with your regulator


The fine idle adjustment was made by adjusting the regulator (big brass screw on bottom of engine. The factory setting for this screw is flush with the crankcase surface.

JeffH

My Feedback: (43)

Some YS 120's will not idle no matter what you do. To fix it, you will have to take the throttle butterfly out and drill the airbleed hole that is in it out incrementally until you get a decent idle. Do some searching in the YS support forum, it should be explained there in good detail. I have been down this road plenty of times with YS's. You can also swap a 120FZ carb on there and that will give you an idle adjustment.