orion1210

HI

my engine, which has just been succesfully ran in, has just suddenly started running way to lean. I've rotated the needle valve anti-clockwise as far as it will go, without removing it, and the engine won't richen at all. I couldn't see any bubbles in the fuel lines but i've checked the tank and fittings and they're fine.

The engine was running fine up untill i made a small 1/8 richening turn on the idle screw to improve the 'throttleability'. The above problem immediately showed itself.

I ran it in using the stock silencer but have now swithed to a bcm pitts muffler, which didn't seem to affect anything to my knowledge during the past week of flying.

HELP!!

Any suggestions greatfully recieved,

Ben

Bax

My Feedback: (11)

You'll need to check the carburetor carefully to see if there's a blockage. Also, it may seem obvious, but when you "richened" the engine, did you turn the idle mixture adjustment the correct way.

Finally, double, and even triple-check the fuel system. Something's made the engine go lean. When it picked up RPM, did you get vibration-induced fuel foaming? That will produce micro-bubbles, which are not usually seen in the fuel lines.

If the needle is as far out as possible without falling out, and you're still too lean, you're getting air somewhere.

If all else fails, remove the engine from the model, put it on a test fixture with all-new tank and fuel lines, and see how it runs there. Usually, if there's a problem in the model, the engine will run nicely on the stand.

Remember, if an engine will run "all day" on the test stand, but not in the model, the problem is external to the engine, or is mixed in the entire system of engine/model/mount/fuel system.

Sporty

Ben, Not having enough backpressure from the muffler can also cause your problem. Make sure the tubing is connected to muffler. Sporty