51' Cub, smokes a little

[Straylight]

Any diagnostics that I can do to isolate the problem? White/Grey smoke at startup and when running. Not a smoke screen but definately smoking, smells like some oil but afraid it may be coolant. Nothing in the oil, coolant level seems to remain steady.

What to look at first?

Straylight.

[Bigdog]

White smoke is usually indicative of water vapor in combustion. Black is running rich and blue indicates oil. You may just be running a little rich in the fuel mixture.

[Donny M]

If the coolant level is good then I would do a compression check.

[mike mix]

One thing to try make sure the crankcase vent tube is clear. This tube runs from the right front of the engine to the air cleaner air inlet tube just above the air cleaner. If you remove the crankcase vent tube from the engine to clean it also remove the fittings from the engine and air cleaner and clean the fittings too. Because of blow by in the engine all engines must properly vent the crankcase pressure. Little or no venting will lead to smoking and oil consumption. If the engine is burning coolant the exhaust will smell sweet if you have antifreeze in the engine..

Mike

[modave]

Hello

My cub smokes really , REALLY bad.

I went out and looked for the vent, i see it come out of the front of the engine, and run straight up then it ends under the hood, and looks to be
crimped off. I am pretty sure the air cleaner is not original , and dont know even if it is where this pipe is supposed to hook up, or where i should 'improvise' hooking it into the cleaner ? any suggestions welcome.

[Bigdog]

It needs to go into the air intake path.

[modave]

before or after the oilbath ?

[Bigdog]

ahead of the oil bath. Here is a picture of a cub air cleaner. You can see the fitting on the air intake tube above the body.