YS 63 S
 

I bought a YS 63 S used. When I got it the valve cover gasket was damaged and leaked like a sieve so I replaced it.
The problem I'm having is that when pressure has built in the tank, the engine transitions snail like from idle to WOT. The longer its at idle the worse the problem is. I got it to run for several flights by backing out the airbleed screw to lean the low end. Of course eventually the low end needle was backed out so far it's in the soybeans somewhere and I ordered a new one. I also ordered the parts to rebuild the carb and I'll probably replace the carb gaskets while I'm at it. Oh by the way, I rebuilt the regulator and the behavior was exactly the same.
My questions are: what if the behavior continues and why did I have to unscrew the low end needle so far out?

Thanks in advance,
Phil

RE: YS 63 S
 

The regulator is too rich,

turn it in (CW) about 1/4 turn and try it again.

The low speed air bleed screw is only effective till about 2.5 -3 turns open past that the air blled hole is full open and can't open any further.

The mid range adjustment is the regulator screw. Once you reset it you may need to adjust the other settings. There are really no parts to rebuild a carb. There is only the throttle barrel seal and rarely does this ever need replacing. If it leaks then the engine will run Lean and your engine is running rich in the middle.


Troy Newman
Team YS Performance

RE: YS 63 S
 

That all makes perfect sense. I hadn't heard the midrange/regulator metaphor. Hopefully just replacing the low end needle and adjusting the regulator will work.
Thanks again,
Phil

RE: YS 63 S
 

Screwing in the regulator helped the transition immensely. But I had to screw it in all the way ( a quarter turn at a time) to achieve this and I still had to turn out the low end needle to 1 3/4 turns. Is it possible the regulator spring has fatigued? I know the regulator is clean and correctly assembled.
Phil

RE: YS 63 S
 

Perhaps check it and see if it is OK and also perhaps that O-ring is leaking a bit. this would cause the pressure on the back side of the plunger to leak away and not close...maybe just a thought.


Troy Newman
Team YS