Crazy spark plug fouling
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Crazy spark plug fouling
The rear spark plug keeps fouling on my 05 sportster. Its a 1200 custom with pipes and HD heavy breather. the spark plug fouls after 20-30 miles. Half of the porcelain is black and the other half is white, like its still brand new. The dealer has done a compression check, that was ok. Changed the jets in four different configurations, that didn't help it. Its been through about 10 sets of spark plugs already and been to the shop 4 times for this problem. they can't figure it out and i don't have alot of money for them to dig for a fix. i'm thinkin valve problem or somewhere in that area. Any one got any ideas? Thanks in advance, Shaun.
the left plug is the rear cylinder and the right plug is the front cylinder.
the left plug is the rear cylinder and the right plug is the front cylinder.
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While the plug in the pics appears to be carbon fouled, your bike is an 05 which has a known issue involving defective valve seals. I don't have the specifics on the Service Bulletin, but there is one out there that calls for the MoCo to replace the valve seals in 05 models.
How much if any oil are you burning over 1,000 miles?
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kirby
vee twin racing
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I didn't think the 05 valve guide seal issue crossed down to the 1200 evolution engine, thought it was limited to the TC88 engine. I would check the carb and float in particular for too much fuel in the float bowl and its being drawn into the engine unmetered. That's where I would be checking. Also do you turn off the fuel petcock everytime you shutdown the bike?