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Old 04-14-2011, 04:58 PM
berndog berndog is offline
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Default keihin spit and sputter

I got an 82 fxwg with a Keihin butterfly carb,,and always spittin and crappin at low speeds pops on decel and runs great wide open,,anyone experienced this? any suggestions?
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Old 04-14-2011, 07:34 PM
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Make sure the float isn't set too high - that'll make it run rich, and at WOT it will often run OK. After that, when was the last time it was rebuilt? Pull it, strip it, clean it, put a good rebuild kit in, and make sure the float is set correctly.
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Old 04-14-2011, 08:31 PM
berndog berndog is offline
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thanks I pulled it apart cleaned it,,rest the float lower,,new rubbers in manifold ,now i think I need carb bracket as it flexes way too much and seems to be sucking air
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Old 04-15-2011, 09:14 AM
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yea sounds like a lean condition to me i had one of them keihin door stops on my bike years back i be riding all of a sudden bike start caughing like it had a two pack a day smoking habit,changed the bands did all the stuff to the carb no change changed it out no problem since
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Old 04-15-2011, 12:16 PM
Horsetrader Horsetrader is offline
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Mine is behaving pretty much the same, but sounds like yours is worse. If you have a bad intake manifold, gaskets, etc. and you are sucking air after the carb, then you will have a lean mix and it will pop on decel. If you are coughing through the carb, same issue, BUT it could be a jetting problem. If you want to keep the orignal Keihin, what you can do is rejet both the low speed and high speed jet and it will help. Use a .88 for the low speed and a .180 for the high speed jet. You can buy these at J&P Cycle Parts. VERY cheap. This will help, BUT it will never run great until you replace it with a better carb. You should also look at your pipes. Have they been replaced? If you are running drag pipes, that will change how your engine breathes and runs too and you will have to rejet accordingly. Valves OK? You should have at least 90PSI in each jug for compression. Less than that and you may have valve and/or ring problems.
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Old 04-15-2011, 06:36 PM
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Sounds like an air leak , could be manifold seals or just wore out shafts & butterfly shaft pivots carb has more than enough age for that . My old S&S B used to eat a butterfly shaft every couple years .
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Old 04-16-2011, 08:53 PM
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Quote:
Originally Posted by berndog View Post
thanks I pulled it apart cleaned it,,rest the float lower,,new rubbers in manifold ,now i think I need carb bracket as it flexes way too much and seems to be sucking air
Yep, no support bracket will cause leaks at the intake manifold.
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Old 04-19-2011, 04:04 PM
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I call that a Government cough! Seems like since they started choking our bikes this has been the result. The Keihin on my '78 FXE started doing that not very long after I got it. Nothing I did would stop it for very long. I finally put an S&S Super E on it and never looked back. Keihin is now a parts part.
I had a Bendex on my '52 Pan/Shov. and it was a good carb except for a hesitation burp at low speed when turning, like a u turn. May have been low float, but I never investigated.
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Old 04-19-2011, 05:30 PM
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Those old Keihins could be made to run very nicely with a little work and a few new parts . Harley started capping the mixture screw boss so you had to drill that and open her a couple turns . A new main jet tube or re do yours if you have the itty bitty jet drills that rare now , add the andrews bigger volume accel pump & re aim the jet so itshot about a 15 deg off center to the front and those behaved very well @ 45 to 50 mpg on stock motors . My S&S 's never got over 40 on a good day .
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Old 04-19-2011, 06:08 PM
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Quote:
Originally Posted by TwiZted Biker View Post
Those old Keihins could be made to run very nicely with a little work and a few new parts . Harley started capping the mixture screw boss so you had to drill that and open her a couple turns . A new main jet tube or re do yours if you have the itty bitty jet drills that rare now , add the andrews bigger volume accel pump & re aim the jet so itshot about a 15 deg off center to the front and those behaved very well @ 45 to 50 mpg on stock motors . My S&S 's never got over 40 on a good day .
Glad to hear you say that. I've worked my '86 evo Keihin butterfly with of all things "a dental tool" to ream the low jet. I had few extra jets on had (just in case), but I lucked out reaming it and for 2 1/2 years that "doorstop" has run great. Never could re-aim the accel tube & the force I was putting on it, let the rear cyl have a most.

Like TwiZted said, I'm proof. Very very few coughs. And starts fine. runs smooth, idles low when Cold. But on an FLHTC I get 40 mpg tops. Before I rebuilt this carb it ran like yours. We have E10 so a rebuild was needed for an aged ride. but always look for intake leaks.... I have compliance intakes so I would check there first.
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Old 04-19-2011, 06:08 PM
 
 
 
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