I have a mower that blows blue smoke and has 120 Psi of compression what gives?

[IsaacTran]

I have a J609 Troy Built riding lawn mower from 2003, it has the Briggs and Stratton 31p999-0293-e2 / intek 18.5 HP OHV engine.


When I start it up I there is usually a small puff of white smoke out the exhaust nothing special and you can ride it and mow just fine. Within maybe 2 minutes it starts puffing out clouds of blue / white smoke that small pretty bad. I best guess what oil was getting into the combustion chamber. I opened up the oil cap and found white smoke coming out of the oil and maybe a bit of pressure released but I’m not sure. Also if I wait a few minutes and start it up again I can again ride it around for a minute before It starts smoking.


I tested the compression to confirm that there was a leak somewhere but I got 120 Psi of pressure when I cracked it over. Now I am stumped. Thing is sealed up tight, but oil is getting in.


Please let me know if you think you know what is going on or if you have any trouble shooting tips I really need this mower.
Thank you

 

[bertsmobile1]

The head gasket is blown
Most likely because the valve lash has not been adjusted for so long that the Automatic decompression is not working & blown the head gasket .
Smoke from the dip stick tube confirms this diagnosis.

 

[IsaacTran]

The head gasket is blown
Most likely because the valve lash has not been adjusted for so long that the Automatic decompression is not working & blown the head gasket .
Smoke from the dip stick tube confirms this diagnosis.

Gatcha makes sense it could make compression becuse the head gasket just blew between the oil and cylinder yeah? I ajusted vales on my dirt bike once before but im a bit fuzzy on this stuff. that means I need to shim the valves to tolerance and then replace the head gasket and I'm all good? Having trouble finding a service manual for my engine or mower...

 

[bertsmobile1]

No where near as difficult.
They have adjusters .
Thousands of videos showing how to do B & S OHV valve lash .
Buy a rocker cover gasket if yours is glued on with silicone.
Pop your favourite gasket goo on the cover side & axel grease on the engine side so it strips off clean in the future.
Check the oil for fuel contamination signifing a leaking carburettor .

 

[IsaacTran]

Thank you!
Ah yes I am looking into it looks like the ajustment is super easy though my feeler gauge doesn't go below .01 inches and I need to go get one that will test under .003 inches tomorrow. I have some high temp RTV gasket for the rocker cover if needed though the gasket looks pretty good I'll order up the head gasket tonight do you by chance recomend a website to get the head gasket from?

 

[Scrubcadet10]

Shop.briggsandstratton.com
Parts Tree.com---- Austin, Texas
Jacks Small Engines ----Maryland
pro parts direct ----- New Hampshire

 

[bertsmobile1]

Thank you!
Ah yes I am looking into it looks like the ajustment is super easy though my feeler gauge doesn't go below .01 inches and I need to go get one that will test under .003 inches tomorrow. I have some high temp RTV gasket for the rocker cover if needed though the gasket looks pretty good I'll order up the head gasket tonight do you by chance recomend a website to get the head gasket from?

Don't put silicone there.
You will spend more time removing it than you do adjusting the valve lash.
Late model engines have silicone & no gasket
Next to impossible to remove the rocker cover then another 20 minutes to clean the cover & the head.
Only good thing is it tells me if the retail dealer actually did check the rocker before delivery as they are supposed to