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Backfiring after carb rebuild

3432 Views 3 Replies 3 Participants Last post by  900SS-SP
Hello all,
I am the owner of a 95 900SS-SP. I hope all you Monster owners will accept me and can help me out.
My bike sat idle for a couple of years due to an arm injury. Along the way the battery died, so the bike was not started and the carbs clogged up with residual gas :-[. Anyway, to make things right I replace the battery and pulled the carbs for cleaning. The electric fuel pump was replaced as well. At first I cleaned the carbs with spray cleaner and blew them out with compressed air. The bike started up ok, but ran rough above 3k rpm and backfired lightly when rev'ed. I pulled the carbs again and soaked them in liquid carb cleaner. The bike now seems to run fine on a brief ride, but still backfires lightly above 3k rpm. I have done all the checks in my manual for the ignition. replaced the plugs and wires. I have adjusted the float height. I have adjusted the fuel mixture screws from one end to the other. The bike has a stage 2 jet kit with K+N filter and D+D exhaust. I have adjusted the needle position both directions. The bike seems to run ritcher or leaner as I do so. I'm starting to think the Ignition is not advancing. how do I tell, or do any of you have any other suggestions. I'm sure I left something else out that I've tried, but that about covers it. Sorry for the long post, and Thanks in advance!

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You haven't clearly stated under what conditions it backfires. When I had the louder, straight through slipons on my bike, it would pop a bit at about 4500 rpms when decelerating if I cracked the throttle just slightly. I almost had to go out of my way to make it happen (okay, I often went out of my way to make it happen ;) ). I've never been able to get any other sorts of backfires from it. My bike has an open airbox and the largest of the three FactoryPro jets with the needles one position leaner than the middle position. It's a bit rich on hot days and at high altitudes, but otherwise it runs just great.

Now that I have lightly modified stock cans on the bike, with a little more back pressure than the slipons, but less than stock cans, the bike no longer pops at all.

So please give us more details about the conditions under which your bike backfires.

If it were me, I would tune the main jets so that it runs right at full throttle, then adjust the needles for part throttle operation and set the idle mixture screws for the best behavior when going from throttle closed to a cracked throttle. Then I would stop worrying about the backfires.

If it really bugs you, you could try to get a little back pressure from the pipes.
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