Oil Burning on Startup

[Guggenheim24]

I have a Briggs 9L902 0284-E1 3.5 that smokes on startup. This past winter I replaced the intake valve seal with an OE one since usually smoking on startup only is caused by that. Valve does not have play in guide either. Still smokes on startup. When I initially pulled off the head, there was a little oil collected between the piston and head. Sitting on the cylinder wall closest to the deck obviously. Not alot. I just find it odd if it was a cylinder wear/out-of-round or ring issue, it would smoke constantly and have low compression. Engine has good compression from the feel of it, and will start first pull; which makes me kind of doubt I have a compression issue. And it doesn't smoke alot and not for long. 2 seconds tops. After that it does not smoke anymore and if I restart hot will not smoke. Only when it sits for a week. We've had the mower since new and the engine has been meticulously maintained with oil changes every fall and clean air filters its whole life. Any ideas? Thanks

 

[Richard Milhous]

Are you sure the smoke is oil, not gas?

 

[Scrubcadet10]

Yep, what color smoke we talking about, Blueish/whiteish or black?

 

[StarTech]

Could simply be over filled with oil and it seeping pass the rings when sitting long periods. Or the cylinder being lower the normal oil level when stored.

 

[olgeezershonda]

Your symptoms sound exactly like a valve stem seal leak to me too. I had a 1980 Pontiac with a 305 that did the same thing - replaced all the valve stem seals and the bit of blue smoke at start up went away. Odd that it would happen so soon after a replacement last winter but worth looking into

 

[VRR.DYNDNS>BIZ]

Could simply be over filled with oil and it seeping pass the rings when sitting long periods. Or the cylinder being lower the normal oil level when stored.

The above is most likely the cause. If oil at the level of the piston because plug is doen hill or slightly over full, oil will weep past rings when stored before next use. If overhead valve engine could be he3ad gasket. All this is assuming the smoke is blue. One last possibility is float failure leaking gas into crankcase and over filling which then causes issues. Also a dirty airfilter or wet will draw hard on the breather and suck oil.

 

[bertsmobile1]

As others have said, smoke on start up only is oil seeping into the combustion space that gets burned off just after it starts.
The problem no one has mentioned is oil that is too thin will also cause this to happen'
Thin oil happens because the engine is overheating or fuel has leaked down into the sump & diluted it.
So check your oil and remove the blower housing & clean the fins .

 

[slomo]

SAE 30 oil is supposed to be at the TOP of the threads at the yellow oil cap. As in nearly over flowing. Make sure the block is level like the pic below when checking.

 

[slomo]

Take a white paper towel. Hold it near the muffler. You are looking for oil or black soot.

Normally smoking on start up only is intake valve seals. Does your engine have one?

Might do a valve adjustment while you are at it.

Also remove the head. Decarbon the cylinder, head and valves. This is in your engine manual.

Clean those filthy engine block cooling fins while you are there too. Again in your engine manual as a yearly to-do.

 

[StarTech]

SAE 30 oil is supposed to be at the TOP of the threads at the yellow oil cap. As in nearly over flowing. Make sure the block is level like the pic below when checking.

View attachment 58801

Please check your post information vs the engine in this post. I think you are advising the OP to hydro-lock his engine but it may just be my brain being flooded with all the rain here this morning.