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Lawn tractor help! (B&S)... Fouled plugs causing foul mouth! by blakeinspace
Started on: 06-14-2011 11:06 AM
Replies: 3
Last post by: James Bond 007 on 06-14-2011 01:04 PM
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Report this Post06-14-2011 11:06 AM Click Here to See the Profile for blakeinspaceClick Here to Email blakeinspaceSend a Private Message to blakeinspaceDirect Link to This Post
The Victim:
a 2005 Craftsman 4500YS
20hp B&S Intek Gold, model 31p977, code 0670e1

The Trouble:
started a Saturday morning mow, and within 10-15 minutes... my mower was WAY down on power. By the time I creeped back to the shed... it seemed like it was barely going to make it. No surging like on and off fuel delivery though...

I pulled the spark plug... and it was fouled. oil fouled, not gas fouled. Very carbonized... I like carbon on fajita meat... not Champion plugs. I had not changed the oil this season, so I put in a fresh load of 30w and a filter, had a spare new plug on hand... slapped it in and am good to go... for... you guessed it... 10-15 minutes. WAY down on power... notice smoking this time in the exhaust.

Creep back to the shed. Pull the plug. Cuss then newly fouled new plug. Hoping for something fuel related... and knowing that I used the local quickie mart running whatever gas is cheapest last time (couple months earlier)... I drained all the fuel... head to a Shell for a few fresh gallons, hit the parts store for a couple more plugs (one to install and one to backup).

New gas in. New plug in. Power is back. For... can you guess? 10-15 minutes. It is a mild smoky return to the shed.

So gents... I can spin a wrench... just not really messed around in the small engine world. If I was to hazard a guess... I would say that I am down on compression due to a blown head gasket which is letting oil into the combustion chamber and fouling the plugs. The restored power comes from a fresh plug and allowing the engine to cool down and regain some of it's 'tightness' then as it gets hot, everything expands and starts the cycle to failure?... just guessing there.... and not sure if that is a hard job to repair. In the auto world, blown head gaskets usually mean lots of parts, lots of time, lots of cussing, lots of money, a couple of trips to the machine shop...

Is there something more obvious that I should check first? Are these symptoms caused by other things? (valves out of adjustment? stuck parts in the carb?)

thanks for the read and I appreciate the help.

<---- did you buy Cliff a beer?

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Report this Post06-14-2011 11:11 AM Click Here to See the Profile for 84fiero123Click Here to Email 84fiero123Send a Private Message to 84fiero123Direct Link to This Post
Auto parts stores sell a plug antifouling tip for your plug. You simply remove the plug, screw it into the antifouling thing. And then screw the whole thing back into the plug hole.

It will save you doing more work but doesn’t solve the problem. The problem sounds like your oil ring is gone. Now that requires getting into the engine. You up to that?
B&S has online manuals that may be of some help as far as working on the engine. Just go to their site and look up your model.


Technology is great when it works,
and one big pain in the ass when it doesn't.

Detroit iron rules all the rest are just toys.

[This message has been edited by 84fiero123 (edited 06-14-2011).]

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Report this Post06-14-2011 11:19 AM Click Here to See the Profile for nmw75Send a Private Message to nmw75Direct Link to This Post
A guy at work was telling me about his B&S powered tractor of the same age. He said that he found out that it is relatively common for those Briggs to dislodge the valve seals.
He said the fix was simple but then again he is extremely mechanically inclined.
Do a Google search for 'Briggs valve seals'. see if what you find matches your symptoms...

86 GT
87 coupe restoration project.

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James Bond 007
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Report this Post06-14-2011 01:04 PM Click Here to See the Profile for James Bond 007Send a Private Message to James Bond 007Direct Link to This Post
A basic guide to engine disassembley.
Your probubley going to need a Briggs & Stratton Overhaul Kit
from what Ive been reading "nmw75" is correct.The valve seals cost about $3.80
Some info here,be sure to check out the posted links.
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