B&S Intek 20hp runs rough

cgrab

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I have a Snapper LT200 that my neighbor gave me when the clutch was worn out. I have since fixed that and used it for two seasons. The following is a short saga you can skip to get to my problem.

The battery had been dying and I had been charging it every so often. I replace the alternator. When I started it, it ran rough with little power. I drove around the yard and then parked it and put out the fire-the paint on the muffler guard caught fire. I then tried to start it again and it backfired. I pulled the flywheel and replaced the key. I checked the mag spacing and I replaced the spark plugs. One was so fouled it wouldn't fire-which led to the actual fire. I then removed and thoroughly cleaned the carb and replaced the gasket. The compressions are about 160 in each cylinder. I get a spark on both sides. The fuel pump works but I don't know what it's output should be.

My problem is that when I start the mower, it runs at high speed for about 5 seconds and then it slows. I can throttle it down but then only throttle it back up about half way before it runs rough and smokes. After about 30 seconds I shut it down and the plugs are fouled again. Usually on one side but not the same side each time. A flaky black foul that is easily brushed away. I get the same results when I try it with the air filter removed.

What should I try next.

Other info: Engine Model 406577 and Nikki carb 796110 with the throttle and choke inline.
 

Scrubcadet10

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Is it black smoke its blowing or blue oil smoke?
 

cgrab

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I think it is a blue smoke.
 

7394

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I think it is a blue smoke.

If Blue smoke I don't see it having "A flaky black foul that is easily brushed away".

Blue oil smoke would get the plug oil fouled & not black flaky..
 

cgrab

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OK but why is it fouling at all and running so rough
 

7394

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If you can do a leak down test, that will tell you..
 

cgrab

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I'll have to get a tester from the parts store but will try to get it done.
 
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