Hi,

I have a YS 63 (not 63 S) that always runs great in first flight (cold). But from the 2nd flight on, it likes to lean out during the flight, normally after about 1 minute after taking off (power drop to 70-80%). Making it rich does not help. The exhause trace is relatively heavy (either in the 1st or subsequent flight). The engine has been "ported" by YS performance, and the fuel is 20/20.

Question: is the rear bearing going bad? What else can cause this?

Thanks in advance

--nsrc

What do you mean "ported by YS Performance"?

Try checking the valve settings to .003"

Whose YS 20/20 fuel?

What prop? What plug?

By "porting" I mean the drilling of several tiny holes on the cylinder. Valve gap is periodically adjusted (to manual's suggestion). Powermaster 20/20 fuel. OS F plug. 13X6 prop. Thanks

You mean gas ported. It's in the piston, not the cylinder.. All engines now produced by YS have the feature, which I introduced them to several years ago. Not my idea, but the first time it was applied to a production model engine.


I have no idea what the problem is with your engine, why not call Richard at service and discuss it with him since they are last to work on it?

My guess is too lean with too much prop, but what do I know?

It was a while back when the porting was done.

This RPM drop problem has been with the engine for a while. Could it be due to the design? I heard 63S is better than 63 in dealing with hot-run situation.

Thanks

None run well when overloaded and under nitro'ed. Try a little less pitch, or 30% heli fuel.

I am thinking of getting this motor for my OMP fusion. will this work on this model? What prop for aerobat use? Also what fuel mix should be used?
Thanks
MIKE

I had a similar problem, found the cause to be over heating during flight.
I just increased the size of the air intake on the cowl.
Engine was sweet after this.

John

Caution on opening up only the air inlet to your engine.
The air OUTLET from from your cowl should be roughly twice the inlet area.
This should have the effect of creating a negative pressure at your cowl outlet.

Otherwise you stand a chance of damming up the hot air inside your cowl.