YS 140L backfire problem
 

Gentlemen

I have been using the YS 140L for a few flights. In the last couple of flights about 1/3 of the time when I climb straight up the engine backfires, kicks and stops. I'm running the engine rich with a nice smoke trail.
Fuel is Powermaster 20/20
plug is the new YS 4 stroke
props are 15 x 12 and 16 x 10 no difference
There seems to be good pressure left in the tank
Any ideas?


Thanks

Backfire
 

I would lean the motor out a little. Depending on how much time is on it, it should get better with time. I had this problem with my latest 120 and after a few tanks it stopped. Also make sure the prop is plenty tight. By leaning it out a little it should not have the problem.


Chris Puckett

YS 140L backfire problem
 

HI RC_MAN,

The YS may still put out smoke if it is a little lean. Backfiring usually means that the YS is a tad lean. Use a tach and make sure it is at least 300 rpm shy of peak until the engine has broken in.


Azhar

YS 140L backfire problem
 

Yep, sounds like a lean condition causing the engine to heat up in the climb and go bang :) The L will not tolerate being run lean for very long so be careful.

Leak free?
 

I had trouble the same as you described when I intalled leak free gaskets. It seemed they were to soft and the little slit in the carb gasket was being squished. reinstalled original plastic gasket and problem dissappeared.

YS 140L backfire problem
 

Thanks for the help