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post #1 of 3 Old 08-26-2014, 10:58 AM Thread Starter
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somewhat off topic

Hi guys and happy summer!! Don't worry, snow season is coming soon enough!!!

OT engine question here on a craftsman mower that's run great for over 15 years. More recently, when I shut it down, as the engine is winding down it huffs some blue out the exhaust. It burns nothing while mowing and the oil is fresh. What do you think, valve guide or rings?

'77 Ariens 924032 "Brick House" Re-Powered with a TEC 10HP and oversize auger pulley
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post #2 of 3 Old 08-26-2014, 11:22 AM
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Quote:
Originally Posted by nt40lanman View Post
Hi guys and happy summer!! Don't worry, snow season is coming soon enough!!!

OT engine question here on a craftsman mower that's run great for over 15 years. More recently, when I shut it down, as the engine is winding down it huffs some blue out the exhaust. It burns nothing while mowing and the oil is fresh. What do you think, valve guide or rings?


if the engine has a little rubber or metal blowby tube connected to intake tract, check that. if the rings are shot, that little tube will be pushing oil blowby smoke. you may not be aware of it because it's being piped back into the intake tract and reburned. but maybe when you shut it down, blowby is pushed into the intake, then cylinder, and out exhaust, and is not burned because the spark is shut off.

bad intake guides would smoke generally all the time. it would draw oil into the intake tract, burn it with the gas, and smoke almost steadily, as it would be diluting the fuel. intake guides generally don't cause blowby because if the rings are in good condition, there's no way for the combustion gases to get into the crankcase via the valve guide. the intake valve is closed on the power stroke. but bad intake guide will cause smoke out the exhaust.

bad rings, will cause blowby into the crankcase, and you'll see that coming out the crankcase vent and the exhaust. I disconnected the blowby tube on the 16HP Gilson tractor Briggs engine, and have it pointing straight down, because I don't want oil dilution of the intake charge- and blocked the round hole in the intake manifold/carb pipe. but I also put rings in the engine for good measure, and honed the block.

do check the blowby tube, see if it's only coming from the crank vent, or the exhaust, or both. disconnect the crank vent and shut it down and see what comes out- also take it wide open running and see what comes out.

put a set of rings in, it will be good for another 15 years ++
you could also do a compression test, and a leakdown test.




just say NO to Chinese made ANYTHING !
1967 S-242 Snowbird 4/24
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Craftsman Drift Breaker 10/32 3-stage
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Yard-Man Snowbird 7040-0 5/22
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(2) AMF Polar Bear 7/26 3-stage project/parts machines

Last edited by greatwhitebuffalo; 08-26-2014 at 11:29 AM.
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post #3 of 3 Old 08-26-2014, 09:30 PM Thread Starter
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I believe it just has a breather that dumps to atmosphere. It doesn't recirculate back into the intake. The smoke definitely comes from the muffler. I'm guessing when the rings aren't under firing compression, oil seeps through.

I'd definitely re-ring it and keep some American... um... aluminum running another 15!!

'77 Ariens 924032 "Brick House" Re-Powered with a TEC 10HP and oversize auger pulley
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