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Discussion Starter · #1 ·
I have been searching alot and can't find my answer. I have a 05' standard (carb) and a stage 1 kit. I just put on a set of pipes that go 1.5 to 2 to 2.5 out. Dual pipes. The bike on deceleration at high rpms backfires like a mother f'er. I rejetted with a 195 main and checked exhaust and still backfires. I rode it last night and when it would backfire flames would only come out of the rear pipe. I will try a 200 main and check the exhaust on the rear pipe again. Any other suggestions?
 

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You're an evildoer.
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HAHA Man that sounds like fun to drive down town.

Is your idle adjusted right? I've had the idle set too low cause this.

Air Leaks (Exhaust Gasket, Exhaust header to muffler area, Carb to Manifold area?

If you are having that much backfiring, unburned fuel is getting in the exhaust and then when the engine does fire - BOOM.

Your main jet has nothing at all to do with your bike when you are off throttle. The Pilot and Mixture are the only two things feeding the mixture to the engine if adjusted right. Too much fuel, or too little can cause that.
 

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Playing with the main to reduce popping in the exhaust on decel will not do a thing.
Check for leaks at clamps or head gasket.
Check idle speed (too high can create popping)
Play with the slow jet (one size up or down)

What pipe do you have? The indy shop that does some work had a softail with long shot style pipe with incurable popping due to the design of the pipes. SE II Pro slip ons did away with the problems
 

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Discussion Starter · #5 ·
Only time I changed the needle was when I did the stage 1. A guy at the shop said to leave the stck 46. No nead to go to a 48.

I do think the idle is a little low. Will try that. I have no mufflers, just straight pipes, and the carb to manifold is sealed good. Will replace the exhaust seals again and see if that helps.
 

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roloplex said:
Only time I changed the needle was when I did the stage 1. A guy at the shop said to leave the stck 46. No nead to go to a 48.

I do think the idle is a little low. Will try that. I have no mufflers, just straight pipes, and the carb to manifold is sealed good. Will replace the exhaust seals again and see if that helps.
What type of exhaust did you run before? 46 slow jet is already one size up over stock 45. Could be that the straight pipes are the problem
 

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Try richening the fuel air mixture screw 1/4 - 1/2 a turn more out from your original setting and see if that doesn't help. If you have to turn the screw out anymore than 3/4 -1 more turn than it already is, you might want to consider moving up to a 48 jet and setting the mixture screw 1 1/2 to 1 3/4 turns out. Worked for me. Stopped coughing and backfiring.

Just my -2$en#e-
Good luck...

DLR
 

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I am running a 195 main and a 48 slow on a 2006 FXST the Bike runs Perfect!!

Also check your idle mixture screw....Direct Parts sells a adjustable one for 20 bucks...its Great! the part # is 5c00 something sorry! but that will get you there.

Cobra Exhaust 3 1/2 " deluxe baloney

Let us know how it works for you!


Ride Safe!
 

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ViennaHog is right. My '02 had a stock 45 slow, originally. Since my 95" install, I've installed the Big City Thunder exhaust wave modifier/baffle in my collecter per Jim's instructions at BCT.

:yikes: Wow, what a difference.:yikes: It came highly recommended from you guys, both in past posts and in my recent inquiry about my exhaust, and improvement suggestions in its application.

Motor has only 40 miles on it so I haven't really rapped it yet, but the power in the low and midrange feels exceptional, (compared to what was an unbaffled Pro Pipe.) I want to get some more miles on it and another oil change and then have it Dyno tuned and see what I learn from that.

I love the looks of the Python 2 into 1 pipe they offer but figure it affords little less than more desirable looks than additional performance over the SE Pro Pipe that I have.

I'm running a "blueprinted" CV 40 that was worked by Kerry Kerstetter, blended and flowed, Dynojet kit, including slide, along with the larger SE 44mm intake, 48 slow and 200 high. It works. Bike runs great, plugs are buring fine.

DLR
 

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My 2006 FLST had a #48 slow jet and a #190 main stock. I put new pipes and intake and bumped up to #50 slow and # 195 main,bike runs perfect.
 

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Wow! the '06s have a 48 slow as stock? I thought with the EPA stuff if anything it would be smaller than 45. Is it still the same CV40? As far as decell poping, not backfiring or reverse firing as in back thru the carb I read a great article by Joe Minton, I believe, last year. As he explains, it is caused by an overly lean condition when the throttle is closed and decellerating. The fuel/air mix is not potent enough to fire on every cycle so these fumes exit into the exhaust and accumulate somewhat. When it does fire it can ignite those fumes in the exhaust. I guess this happens with most internal combustion engines, we just don't hear it until we change to a more open exhaust or the idle circuit becomes too leal.

I tried this lst year. I changed the idle screw setting from 2 1/2 or 3 out to maybe 1 or so out. The bike sounded like a machine gun at 1 or so and disappears at 2 1/2 or so.

If you are decellerating from high rpm with the throttle closed I believe only the idle circuit is involved. The slow or main jet don't come into play until the throttle is opened to some degree, so don't touch em.

If I am wrong with any of this, please correct me. Just like Mulder, I search for the truth.


SOAB Tried to post this and got logged out for the 5th time today. Hope I haven't repeated an answer.
 

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roloplex said:
I have been searching alot and can't find my answer. I have a 05' standard (carb) and a stage 1 kit. I just put on a set of pipes that go 1.5 to 2 to 2.5 out. Dual pipes. The bike on deceleration at high rpms backfires like a mother f'er. I rejetted with a 195 main and checked exhaust and still backfires. I rode it last night and when it would backfire flames would only come out of the rear pipe. I will try a 200 main and check the exhaust on the rear pipe again. Any other suggestions?

Iam having the exact same problem with my 03 fxdwg. Iam running V&H Big Shots pipes. Let me know what you find out. Thanks.
 

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Leak

Of course you may have a jetting problem but if you are back firing and flames are shooting out it is most likely an exhaust leak. It is probably where the muffler slips onto the pipes. You may feel it if you hold your hand near there. Get some high temp silicon exhaust sealer (orange in color) butter the inside of the muffler before you slip it on to the pipe, wipe off the excess that oozes out and tighten the clamp. It will take 24hrs to cure the sealent. Make sure that the clamp is on straight when you tighten it. Due to manafacturing, etc. the fit of the muffler to the pipe isn't exact sometimes requiring the silicone to be used. Oh yeah....try to clean the inside of the muffler as best you can at the joint so that the silicone will adhere to it.
Hope it works!
 

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02Blue said:
Of course you may have a jetting problem but if you are back firing and flames are shooting out it is most likely an exhaust leak. It is probably where the muffler slips onto the pipes. You may feel it if you hold your hand near there. Get some high temp silicon exhaust sealer (orange in color) butter the inside of the muffler before you slip it on to the pipe, wipe off the excess that oozes out and tighten the clamp. It will take 24hrs to cure the sealent. Make sure that the clamp is on straight when you tighten it. Due to manafacturing, etc. the fit of the muffler to the pipe isn't exact sometimes requiring the silicone to be used. Oh yeah....try to clean the inside of the muffler as best you can at the joint so that the silicone will adhere to it.
Hope it works!
i hate to be the next guy that takes it off
 

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This is not a problem guys. So much air gets sucked in through the pipes on high RPM decel that it causes a temporary lean condition which goes bang. Enjoy it. It's great under overpasses.
 

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roloplex said:
Only time I changed the needle was when I did the stage 1. A guy at the shop said to leave the stck 46. No nead to go to a 48.

I do think the idle is a little low. Will try that. I have no mufflers, just straight pipes, and the carb to manifold is sealed good. Will replace the exhaust seals again and see if that helps.
No mufflers, as in unbaffled? Sounds like a candidate for at least a 48 slow jet. And the carb to manifold might be sealed good, but what about the manifold to the heads? That's where I've seen most of the problems with spitting and backfiring. But if it's just popping on decel, I'd put in a 48 slow and set the idle to about 1000 with pipes that open. :xhere:
 

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chnpostal said:
No mufflers, as in unbaffled? Sounds like a candidate for at least a 48 slow jet. And the carb to manifold might be sealed good, but what about the manifold to the heads? That's where I've seen most of the problems with spitting and backfiring. But if it's just popping on decel, I'd put in a 48 slow and set the idle to about 1000 with pipes that open. :xhere:


Update on my backfiring, took it in to dealer and had them tune it. They put in a #48 slow jet got me 5 more horsepower and 3 ft lbs of torque. No more backfire and the bike is quite a bit smoother. Thanks for the advise on the jet change :thanks:
 
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