Two Gas Engine Running Questions/problems
 

1. What are the possible causes of excessive vibration at idle other than loose engine mount, out of balance prop & bent crank shaft?

2. Can someone give me some causes for engine pulsing/surging(?) during flight at mid to medium high throttle settings in steady state flight.

This is in a 30cc engine with a 2-blade 18x6 prop.

thanks.

RE: Two Gas Engine Running Questions/problems
 

Tuning, either carb or ignition or both.

Sincerely, Richard

RE: Two Gas Engine Running Questions/problems
 

Add air leak to the mix, plus diaphragm pressure issues. If you have a leak in the fuel system you can be developing large voids in the fuel delivery,

RE: Two Gas Engine Running Questions/problems
 

I agree with T.O.M. 100%....he is right on the ball ....giving good data. http://www.rcuniverse.com/forum/js/f.../thumbs_up.gif Capt,n

RE: Two Gas Engine Running Questions/problems
 

ok, thanks, I don't think it's a fuel line issue. probably going to send the engine in for maintenance.

RE: Two Gas Engine Running Questions/problems
 

The first thing I would check is the filter screen in the carb. If it is surging in flight at half throttle sounds like it's starving for fuel. If the screen is OK it could just be rich on the botton end. I usually like to lean the low needle until I notice a bog in transition then richen just enough for the bog to dissapear. This should be done at operating temp wich means when cold it may bog or hesitate until the temp comes up to normal

RE: Two Gas Engine Running Questions/problems
 

I think I'll take the carb apart and check. Is there anything to check on the diaphram other than just seeing if it has a hole in it.

RE: Two Gas Engine Running Questions/problems
 

If the diaphragms are stretched or billowed out, they should be suspect.