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Buell Forum » Old School Buell » Archive through August 27, 2011 » Carb farts and backfires « Previous Next »

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Sgtshap
Posted on Sunday, August 07, 2011 - 02:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

What could be causing this?

Ill warm the bike up, it'll idle fine. Ill start riding and itll "POP" with a complete lack of power during that POP and then continue. Its like the cylinder doesnt fire, or backfires.

Itll happen in lower rpms, under 2,500, like when im just cruising or maintaining speed. When I get on it its VERY strong, but in the lower ranges it does this. And not just once. Itll do it randomly once every few seconds until I open the throttle and go for it.
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S1owner
Posted on Sunday, August 07, 2011 - 03:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Welcome to buell
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01x1buell
Posted on Sunday, August 07, 2011 - 03:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

i am sure that twoseasons will have something to tell you about this.
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Midnight_rider
Posted on Sunday, August 07, 2011 - 07:27 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

sounds like you need to raise
the slide needle ( more fuel)
which means lower clip
i'm guessing lean condition
about 1/4 throttle

maybe?
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Buell_bert
Posted on Monday, August 08, 2011 - 12:54 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

A couple questions should preclude a diagnosis. Did it just start doing it? Did it always do it? Did you do something and it started doing it? Did someone else do something and it started doing it?
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Hellraged
Posted on Monday, August 08, 2011 - 04:29 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

i know this is simple and stuff but have you tried no ethanol gas? when i put some bad gas in my bike it farts and back fires.. but when i put some good quality gas in there runs good.
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Guell
Posted on Monday, August 08, 2011 - 10:00 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

10% ethanol wont affect the way your bike runs unless its way way out of tune.
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Natexlh1000
Posted on Monday, August 08, 2011 - 10:07 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ethanol will make it run a little more lean.
If it was on the edge of being lean already, the addition of %10 ethanol could be all it needs to make it run crappy.

Just fatten up the mix a little bit.
Did you already remove the metal plug from the carb and adjust the pilot screw?
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Sgtshap
Posted on Monday, August 08, 2011 - 12:17 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

havent done any carb adjustin yet. Is there a sure proof way of seeing if I am rich or lean?

If I can figure out its one of those, then I can get the step by step from mikunis website.
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Velocity
Posted on Monday, August 08, 2011 - 02:32 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Usually a backfire in the air cleaner means lean, a backfire in the pipe is rich. Sometimes the idle mixture screw vibrates out. Plus if it still has the lead plug, then you know its lean,

Scott
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Sgtshap
Posted on Monday, August 08, 2011 - 02:56 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

ill check the idle mix screw. I played with it last week and i thought i had it right. Whats the lead plug you are referring to?
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Guell
Posted on Monday, August 08, 2011 - 02:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

just a note, he is running a hsr42, not a cv 40.
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Jumbo_petite
Posted on Monday, August 08, 2011 - 03:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

have you checked the intake boots for vacuum leaks?
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Hellraged
Posted on Monday, August 08, 2011 - 05:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

well ethanol gas doesnt make my bike run like crap , but its the quality of gas i was talkin about, i try to go no ethanol because the gas is better quality, but say you go to a "indian" gas station my bike will run like crap or a noname place or w/e but when i get good quality gas it purrs like a kitten :P is all
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Guell
Posted on Monday, August 08, 2011 - 06:33 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

what about an bp store owned by indians? I dont think race has an issue with it, maybe a no name gas station but not race...
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Jim2
Posted on Monday, August 08, 2011 - 07:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Check your header for cracks/holes. Esp in the back where you can't see the hair line cracks.
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Hellraged
Posted on Monday, August 08, 2011 - 07:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

lol a bp is good, im talkin about a no name gas station..has nothing to do with race just a fact. well around where i live anyways..
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Sgtshap
Posted on Monday, August 08, 2011 - 09:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

ok so we have a few things here,

Bad gas
Cracks in header
Vacuum boots (???)
lean condition...


Its been doing this ever since i got it, and the previous owener said that its been doing it for him too. he thought it was running rich because the previous before him put the hsr42 on it and didnt properly jet it for the vance and hines exhaust and s&s intake...

Should I just take it to a shop and let them have at it? That way they can have it on a dyno and tune it in for me.
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Hellraged
Posted on Monday, August 08, 2011 - 09:55 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

dyno tuning wouldnt hurt :P i havent done it on mine but i really want too, .. i read somewhere on the net you can look at your spark plugs to see if its running lean or rich, google it and see its the old school way i heard lol just what i heard on the net not my experiance btw . oh i just remembered. on my bike when it was running bad like farts and what not out the carb, i realized my S&S airbox was too tight on the carb basically wasnt getting enough air in there because of how tight i had it and stuff, i backed off the screws a bit and it works better than ever, maybe try something like that? dunno what kind of air breather you got =/
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Sgtshap
Posted on Monday, August 08, 2011 - 10:36 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

ive taken the s&S off and went with a small cone style filter, K&N.

But the pops were and are still the same.

I changes the plugs, and the look good (used the oldschool chart)

I think Im just going to take it to moto mechanica or mamoth motorsports to have it looked at and dyno'd
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Sgtshap
Posted on Monday, August 08, 2011 - 10:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

this way instead of doing a never ending guess an check, I can get it tuned in and go from there.
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Cyclonecharlie
Posted on Monday, August 08, 2011 - 10:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Make sure the vaccum line from the VOES is connected(if it's still using one) But most likly it's just too lean in the mid-range(raise the needle a notch)
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Firemanjim
Posted on Tuesday, August 09, 2011 - 01:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

SGT, What plugs--seen 2 tubers with the old 6R plugs,all Buells supposed to get the 10R's now.And Most Mikunis will come jetted lean as alot are aimed at Sportsters. Had one today,160 main,way too lean.
Our shop is just down from you at Infineon,bring it on down and I can see how it is running.
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Sgtshap
Posted on Tuesday, August 09, 2011 - 11:16 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

whats your shop name, adress?
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Firemanjim
Posted on Tuesday, August 09, 2011 - 01:38 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

JT&S Performance,29731 Arnold Dr.Infineon Raceway, 707 996-6103.Working on an S-1 right now.
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M2marc
Posted on Tuesday, August 09, 2011 - 08:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

air leaks will casse a backfire through the carb. check to make sure the air filter is secured and that there isnt a crushed area. exhast pipe bolts.... if they are loose air can get sucked up into the carb.
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Mmesa005
Posted on Friday, August 19, 2011 - 05:05 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Sorry for the late response - I just went through this with my 04 Sportster XL1200R with Screaming Eagle II mufflers and air cleaner assembly.

In short the mixture was set too rich due to leaking intake manifold gaskets, the seal between the carburetor and the intake manifold and the seal between the air cleaner backplate and the carburetor was torn as well.

I think due to the vibration of the sportster engine these seals wear out every few years.

I had just purchased the bike and went through troubleshooting to find the causes of the back firing and poor acceleration.

I also checked the float level (which was fine) and while I was in there checked the jet sizes (45, 175), the needle jet, and vacuum piston and boot and cleaned the carb inside and out.

I also ran SeaFoam through the fuel system.

I also replaced the enrichener while I had the carb off as it was not operating smoothly.

@ $40.00 in parts from the Harley dealer.

Last, I pulled and cleaned the plugs, checked that the terminals where screwed on tight and that the gaps were .040. Also made certain the wires had not cuts and the boots were seated tightly at both ends.

The bike is day and night better now!

(Message edited by mmesa005 on August 19, 2011)
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