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Join Date: Nov 2007
Location: Chandler, Arizona
MOST of the time spark plugs that spark outside the engine will spark inside the engine under compression, there are rare exceptions, and I don't know what causes it. New plugs usually solve the problem.
I am confused about the pilot screws. The pilot screws and idle air/fuel mixture screws are one and the same. They are on the side of the carbs, under a pressed in plug. I removed my plugs, and turned them out somewhere between 2-1/2-3 turns. I found I have to turn them back to 1 1/2 turns to pass emissions. Hope that goes away soon. Law was passed doing away with it for motorcycles over a year ago. The only other adjustment on the outside of the carbs is the idle speed, which is a large black plastic knob on the left side of the bike.
It is possible that soaking the carbs in Seafoam did not get them clean enough, Seafoam is great stuff, but can only do so much. You may still have to remove them and clean them, though if it is better you can try Seafoam again. It will never get the carbs completely clean, but it may get the jets open, so it will run right.
Hopefully the enricheners on the carbs are ok, not something to mess with until you have tried everything else. You can check where the enrichener cables connect to the carbs, and make sure nothing is loose or broken, and you might try lubricating the cable, and checking it for damage. Also make sure the throttle cables are ok and properly adjusted.
One of the modifications I made to my bike that I do not recommend (though I don't see how it could possibly be any worse than K&N air filters) was to remove the "push" throttle cable. By having only one cable, there is a lot less drag on the throttle, it is easier to open and close, and I noticed it "snaps" closed much faster when fully opened (with the engine off) and released. While it definitely works much better, the reason I don't recommend it is because there is supposedly some safety issue with doing it. I don't see one, if the cable breaks, the spring will close the throttle, and as a last resort the kill switch is right under your right thumb. Many Japanese bikes came with only one throttle cable, I own 3 of them. But as long as someone says '" safety issue" I cannot recommend it due to liability issues.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike