kennethcolesiny

I need help to correct a problem with this engine. I'm using 15/20 fuel, after 2 gal of use and running a little on the rich side, after 5 minutes into the flight, engine seams to lean out and overheat. I bring it in right away. This is new to the engine. I'm getting plenty of smoke with a full tank of fuel, so I know I'm starting out on the rich side, what can I look for? A club member said I might need a valve adjustment. What say you? Thanks for any help. Ken

w8ye

My Feedback: (16)

The engine prefers a 13-6 or equivalent prop. Could be overheating?

You could be getting bubbles in your fuel tank and leaning the mixture?

Could be carburetor ice? This will drive you nuts and disappear as suddenly as it came.

Enjoy,

Jim

Rv7garage

My Feedback: (10)

Funny, but I was just wondering the other day if our small carbs would ice up just like our full-scale brethren. Same physics, I guess

It definitely sounds like you're overheating, otherwise you would have a problem right at startup, and not after flying for 5 minutes. Is your engine cowled, and if so are you sure that your inlet/outlet cutouts are correct in size and placement for good cooling?

I'm Running a 14x6 prop on my O.S. 70 Ultimate, and while that may be pushing it a little bit, she still tachs out at 7800 and runs very consistantly-all day long in a fully cowled setup- so I would not think that the prop was the first culprit (*unless you're running bigger than that??!!)

What plane is the motor in?

Also, you cannot tell how rich your four-stroker is by the quantity of smoke- you must use a tach. It is quite possible that you are running lean and overheating- maybe the needle got bumped?

rctrax

I would deffinatly check the valve lash, espiaslly the exaust valve as when it heats up after a few minites the valves might be getting tight and starting to hold open and lose power. I have had this same thing happen to me and went the longest time tearing my hair out before someone suggested to open up the valve lash a bit.I have found that the exhaust needs to be a little looser than the intake, still within the tolerance window.

w8ye

My Feedback: (16)

Does this plane have a cowl on it? If so, try the engine without the cowl?

Enjoy,

Jim

kennethcolesiny

Thanks for the tip. Several people asked about the cowl. And a few asked about the prop size. I did not change anything.

Another club member said what you said, but I did not want to suggest that. Thanks again. Ken