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carbs backfiring up into airbox... what's the cause?

Old 08-10-2006, 08:26 AM
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carbs backfiring up into airbox... what's the cause?

I went for a ride yesterday and it was doing this a LOT. I've never had it do it so much. something wasn't right. I'm half thinking that it's just straight rich now and since I'm still running a stock filter that a k&N should lean it out, but I'm really wondering if this is also maybe a sync issue as well as maybe something entirely different like my carbs are having issues (I've cleaned them twice, 1st time I wasn't very thorough, did it again when I installed new jets). So either someone locally helps me figure this out or I might be stuck taking the bike to someone to smooth it all out once I throw in a filter and fill in the holes in the airbox as well as block offs... but that's gonna be $$$$$$$$
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Old 08-10-2006, 10:21 AM
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In my automotive experience a lean mixture causes backfires through the carb... Your spark plug color should tell you whether your running rich (black soot on them)
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Old 08-10-2006, 02:25 PM
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Mixture screws should be at about 2 turns out for best idling and just off idle response. Rick is right about being lean. A good carb sync will help as well. You still have the Erion cans? If so, then try 2.0 to 2.25 turns.
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Old 08-10-2006, 02:31 PM
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i went with the dynojet recommendations of I think 2.5 I believe (whatever it said I did)... still erion but no filter. i found it hard to believe that I'd be lean though... I put in BIGGER jets then I had before because it had some stumbling and it ran better afterwards and the needles have remained on 1 from the top notch as directed by dynojet. Bad gas maybe? I need to get someone here that knows more then me to help me out...
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Old 08-11-2006, 12:09 AM
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would adjusting the mixture as well as getting new pilot jets help? WOT is fine. it's partial throttle that's killing me
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Old 08-11-2006, 06:58 AM
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you could still have some gunk in the carbs thats restricting the fuel flow in the low speed circuit even though you put bigger jets in... It may be worthwhile to get some carb cleaner and soak the carbs overnight - some auo part stores sell a can of it for that purpose, kinda like a gallon paint can... I have seen it recently at Advance Auto Parts. Remove the rubber parts and anything else that may not like soaking in carb cleaner and let them sit. This method works well for gunked up automotive carbs.
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Old 08-11-2006, 07:23 AM
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WHOA!!! No filter???? I think that's your problem. Try with a filter and the problem will more than likely go away. This airbox is sensitive to any changes including filter type. Having no filter at all will play havoc with your carbs.
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Old 08-11-2006, 07:30 AM
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Factory settings are 2 3/4 turns out. Sounds like you need to install a filter.
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Old 08-11-2006, 07:48 AM
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Originally Posted by RickB
you could still have some gunk in the carbs thats restricting the fuel flow in the low speed circuit even though you put bigger jets in... It may be worthwhile to get some carb cleaner and soak the carbs overnight - some auo part stores sell a can of it for that purpose, kinda like a gallon paint can... I have seen it recently at Advance Auto Parts. Remove the rubber parts and anything else that may not like soaking in carb cleaner and let them sit. This method works well for gunked up automotive carbs.
Simple Green works well too and you can get it at the supermarket.
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Old 08-11-2006, 07:50 AM
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I think/hope he means no aftermarket filter?
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Old 08-11-2006, 08:48 AM
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Originally Posted by Hawkrider
WHOA!!! No filter???? I think that's your problem. Try with a filter and the problem will more than likely go away. This airbox is sensitive to any changes including filter type. Having no filter at all will play havoc with your carbs.
no filter aka no aftermarket. it's a stock filter. sry for my poor wording
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Old 08-11-2006, 09:44 AM
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Never thought of trying it inside a caburetor, didn't figure it would cut through gum/varnish found inside them - it does work well for external cleaning of them, degreasing engines, etc

Originally Posted by superhawk22
Simple Green works well too and you can get it at the supermarket.
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Old 08-11-2006, 10:33 AM
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Originally Posted by RickB
Never thought of trying it inside a caburetor, didn't figure it would cut through gum/varnish found inside them - it does work well for external cleaning of them, degreasing engines, etc
Yeah, it was a tip from my brother that he learned at AMI a few years back. Plus it's a lot easier on the skin, lungs, pets etc...
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Old 08-11-2006, 11:23 AM
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your lil brother wanna tell me how to get my bike running smoothly? lol
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Old 08-11-2006, 02:27 PM
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Sure drive it on down here but I'm the little brother.
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