Cleaned engine head, installed new plug, received black carbon, runs rough

I have a Bolens chipper/mulcher with a Briggs and Stratton 5 hp motor, given to me by my father-n-law. It had been setting awhile but not before he drained out the fuel before storage. It ran rough with new gas and pinged. I maintenanced it and it still runs rough and immediately carbons up the new spark plug. So I need to know what to try next. Here is what I have done so far:

Maintenance...

1) replaced the spark plug
2) replaced the air filter
3) Did not remove the carburetor but opened the side and top (choke area) and sprayed Gum-Out to and used air to blow out dry. cleaned the fuel/air mixture needle and the inside before re-inserting.Then closed everything up. Played with the needle between closed and 2 full turns.
4) Removed the head and as delicately as possible, cleaned all the carbon build up on the piston and valves.
5) Cleaned the flywheel magnet of rust and the end of the coil, re-gaping using a business card.

Remaining symptoms...

I suspect a fuel mixture issue but think it may be a combination and can't determine what to try next. Here are the current symptoms after some maintenance:

1) Runs rough as before, like it is missing, just no ping sound since cleaning out carbon build up at the head (i.e. piston, valves).
2) Choke closed - won't start but choke open in run position, it will.
3) Fuel/Air mixture needle seems to have no affect whether closed or opened.
4) Fuel smell - I think it is getting too much fuel as one cause but closing the needle doesn't seem to matter
5) Spark plug immediately turned black with carbon just running about a minute at rough idle -- not sure needle had an impact.
6) If I take the air filter off, and run some air over the carburetor with the air compress it seems to run smoother -- but that is with the fuel/air needle closed or sometimes slightly opened.

How about you start with giving us the model number of the engine so we can see which one of the 5000 varieties of briggs 5 hp engine you have.

ILENGINE said:

How about you start with giving us the model number of the engine so we can see which one of the 5000 varieties of briggs 5 hp engine you have.

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Unfortunately it's not available. The usual location marking / label with the Briggs and Stratton model information either was removed or weathered and came off. Any suggestions? The Bolens model is MC2500 but couldn't find anything stating the engine information.

Those old engines actual have the numbers stamped into the blower housing. Normally would be located next to the spark plug, but could also be down the side of the blower housing. I have seen engines that they ground the numbers off of when they were sold as second hand through rural king. There should be grind marks where the number were, or they could be rust covered and may take some scratching to find them You may also try posting a picture of the engine and we may be able to get the model number close enough to help you out.

Ok SV How about a couple pics or a video..... That would help a lot >>>>>>>>>>

Model: 1302232; Type: 3162 01; Code: 89[9]50601 (uncertain 3rd no.)

See attached pics. The forum attachment manager doesn't accept mp4 videos. Runs like it is missing and black soot type smoke out of muffler (see first post for details) Hope these help.

take the valves out see of they need a lap.

Remove the carburettor and clean it properly
You will find instructions here http://outdoorpowerinfo.com/repairs/briggs_pulsa-jet_horiz_fixed.asp
Buy a full rebuild kit for the carb and replace the needles. they will most likely have big groves in them.
Please read the instructions & try to use the names of the parts in the article as it makes it a lot easier to folow what is going on.
Remember you have the engine in front of you and all we have is a screen.

I hate videos & am glad the site does not allow them to be posted.

99% of them are shakey, at obscure angles, out of focus and have poor sound quality.
Stills are usually much better for us to work with.

EngineMan said:

take the valves out see of they need a lap.

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Lapping the valves worked! I didn't know what that was about, but researched, bought the lapper tool and valve compound, and it worked.

Thanks!

bertsmobile1 said:

Remove the carburettor and clean it properly
You will find instructions here http://outdoorpowerinfo.com/repairs/briggs_pulsa-jet_horiz_fixed.asp
Buy a full rebuild kit for the carb and replace the needles. they will most likely have big groves in them.
Please read the instructions & try to use the names of the parts in the article as it makes it a lot easier to folow what is going on.
Remember you have the engine in front of you and all we have is a screen.

I hate videos & am glad the site does not allow them to be posted.

99% of them are shakey, at obscure angles, out of focus and have poor sound quality.
Stills are usually much better for us to work with.

Click to expand...

Lapping worked for this post issue. However, this is good advice on another engine I'm working on. I found a power washer in the trash and the owner said it wouldn't run. When I go it home the gas was thinner.

Thanks!