flyintexan

My Feedback: (1)

My dad has been flying a H9 cap with a YS120nc for some time (he lives in NY, I'm in TX). Recently though, he says the transition from idle to top end is very slow. It does not quit in flight, but just takes a while to come up after being at idle for any length of time (stall turn). He has changed plugs, adjusted valves, adjusted the needle a bit, but no luck. I'm thinking there are several things to check, but if anyone has a list that can be put in order of easiest first, it would be greatly appreciated.


TIA,
mark

jayjayneri

Close the regulator screw by 1/8 turn at a time until the idle improves. Should need no more than half a turn total. Let me know how it turns out.

iflyrctoo

Hey Mark,
It sounds like an air leak to me. It may be something in the regulator but usually when a YS is running good and something suddenly changes, It's usually an air leak. Check the valve cover gasket, the carburator gasket, The O-rings on the pushrod covers or the O-rings on the intake pipe from the carb to the head.

Joe

flyintexan

My Feedback: (1)

Thanks for the prompt replies. Adjustments were tried on the regulator and needle to no avail. This engine has the original gasket set (old engine but not taken out of the box until a year ago...), so I suspect a leak as well. He is going to look over the engine for possible leaks and replace the valve cover gasket immediately since he has been recently checking the valve clearances....


thanks again,
mark

apereira

I had the same problem, the engine had good power but after two minutes the same thing you are describing happened to my engine, I solved the problem by replacing the piston and ring only, and it is running like a new engine now, I just forgot how much power my engine could deliver, this was after talking to the guys at Central Hobbies.

Good luck.

toddblose

My Feedback: (10)

Mark,
Have your Dad look at the check valve. if it goes bad than you will lose the pressure
in the tank.

Jimbo952

Check valve is likely Leaking and overfueling the midrange and causing your poor accell. Blow through the check valve backwards, If it does not check instantly then it is bad.

flyintexan

My Feedback: (1)

Two things seem to have solved the problem....valve cover gasket did not look good ...AND.... 15% nitro fuel.......yuk (had been running 20/20 and I was not initially informed that he changed fuel). Replaced valve cover gasket and inserted some 30% fuel and all is well again.

Many thanks for all the help and suggestions.