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Until we meet again
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Discussion Starter #1
Honestly, it's a lot louder than many gunshots I've heard, so I'm pretty sure it's a backfire.

Bike has recently learned a new trick. Start it up and run for hours, bike runs flawlessly. Stop for a long gas station break (10 - 15 minutes) at the top of a hill. Restart, go down the hill and use some engine braking in the first 2 minutes, listen for a .45 caliber handgun to go off. If the hill is long enough you may hear several shots. It has become pretty predictable and only happens after a warm bike has been cooled and restarted. After the first few shots it never does it again.

After the fist few I rechecked all the boots and everything was seated properly. Not really sure what else to check. I've just hit the mileage where I could do another valve check, but considering how little they moved between the last two checks I'd be surprised if they are out of spec.
 

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"Ride for hours. Stop for gas at the top of a long hill. Take a 10-15 minute break. Restart and go down a long hill, engine braking for two minutes. Listen for a few shots, then they never happen again."

Seems like a lot of work to replicate the noise.

Sort of like when you say to the doctor "It only hurts when I do this!":mrgreen:
 

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FORUM GODFATHER.....R.I.P. PAT
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Check the TPS adjustment. It should look like -C00 at idle and the dash should go to the top of the C above idle. John Weldon likes the dash to move at about 1800RPM but that's a TL1000 spec. A bit higher may be okay. It could also be a variant on the bad TPS syndrome where the bike won't idle right after it is warmed up since engine braking is essentially holding the engine at an idle throttle setting though in motion.
 

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My G/F's 97 HD Springer does it a lot and her 06 1700cc Warrior does it once in a while, when they're hot and engine braking. A M/C techy friend said they're loading up with some fuel and the hot exhaust is lighting off the extra fuel. So the TPS makes sense.
She got a new TPS on the Warrior, it helped a lot. The HD, well it's a HD, ride it 2 hours work on it 6 hours.
 

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Until we meet again
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Discussion Starter #5
Check the TPS adjustment.
I'll give that a shot. I put a new TPS unit in about 6 months ago when I was trying to track down something else. It's possible it has moved since then. I'll take a look.
 

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a leaky exaust will pop & backfire, however seems like it would do it more often unless the exaust doesn't start leaking till its heated up enuf

I just had to replace all the exaust clamps on my Vee, you have to buy aftermarket clamps, oem clamps are tackwelded to the muffler and are not available as a separate item



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That was what mine did before Yosh box remap to cure the lean condition. Long decel engine braking situations, I'd get a really loud backfire. Along with some stumbling and surging under 3000rpm. Almost every ride I could expect to get a good backfire at least once, and it would usually catch me off guard and scare the :yikes: out of me. lol
 

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Until we meet again
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Discussion Starter #9
That was what mine did before Yosh box remap to cure the lean condition. Long decel engine breaking situations, I'd get a really loud backfire. Along with some stumbling and surging under 3000rpm. Almost every ride I could expect to get a good backfire at least once, and it would usually catch me off guard and scare the :yikes: out of me. lol
Yep, always on long decel. But only after the bike had cooled some.

They more annoy me than scare me. But MZBuckeye has been following me for the last 4 days around West Virginia and I think a few gave him a pretty good jump. Especially the one that happened under a highway overpass. Really reverberates down there. :green_lol:
 

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?..Bike has recently learned a new trick. Start it up and run for hours, bike runs flawlessly. Stop for a long gas station break (10 - 15 minutes) at the top of a hill. Restart, go down the hill and use some engine braking in the first 2 minutes, listen for a .45 caliber handgun to go off. If the hill is long enough you may hear several shots. It has become pretty predictable and only happens after a warm bike has been cooled and restarted. After the first few shots it never does it again.
...
Are you remembering to pay for the gas.
 

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Until we meet again
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Discussion Starter #12
Check the TPS adjustment. It should look like -C00 at idle and the dash should go to the top of the C above idle. John Weldon likes the dash to move at about 1800RPM but that's a TL1000 spec. A bit higher may be okay. It could also be a variant on the bad TPS syndrome where the bike won't idle right after it is warmed up since engine braking is essentially holding the engine at an idle throttle setting though in motion.
Bike was centered at idle and the bar moved up at about 1350. I've adjusted it so it moves up around 2000 now. Rechecked the TBS and was still good. May take a while before I have the right conditions again, but will report back if this fixed it.
 

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Until we meet again
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Discussion Starter #13
It's definitely a little different. I had temp up to two bars before leaving for my ride today. It gave me two little pops by the time I made my first stop 1/4 mile down the road. Never did that before, not on the initial heat up portion of the ride. That was always smooth. After those it ran incident free for about 75 miles when I stopped for 5-10 minutes.

Back on the bike I tried to reproduce the big bang and couldn't get one. Instead I would occasionally get real little pops. I'm sure more noticeable to me than anyone listening.

Overall I don't feel the bike is running as smoothly now. Almost feels like an out of sync throttle body, not completely like a bad TBS...just not as smooth as it should be. Strange because I looked at the TBS the other day and it was pretty good.

I'm going to go back under the tank to see if some of the big bangs possibly blew off one of my boots. Haven't checked since that happened. If that doesn't work I'm thinking about zeroing out my PCIII just to see what happens.
 

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Until we meet again
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Discussion Starter #14
Alright, I went back through it again. The TPS was still good, but I did find that I could make an adjustment to the TBS. It's now gone from a .45 caliber to a .22 short, so it's better. I have not zeroed out the PCIII yet.

I was wondering, how do you check to see if you have an exhaust leak? And how do you fix it? Since this is new behavior I'm inclined to think something changed rather than a map all of a sudden becoming a problem.
 

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My V started doing that when it had about 60k miles on it. I couldn't find any problem. It now has 120k and still does it. I gave up on trying to fix it a long time ago.
 

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I was wondering, how do you check to see if you have an exhaust leak?
One way is to plug the pipes while the bikes running, if it stalls, you don't have a significant leak.
 

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Until we meet again
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Discussion Starter #17
One way is to plug the pipes while the bikes running, if it stalls, you don't have a significant leak.
Thanks buddy. I know I can always count on you for technical advice. :green_lol:
 

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I'm a little late to this party

I'm trying to figure out what y'all are talking about here, and I'm real confused. Are you having a "backfiring" or "afterfiring" condition? The backfire happens in the intake tract, and the afterfire happens in the exhaust.
 

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Until we meet again
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Discussion Starter #19
I'm trying to figure out what y'all are talking about here, and I'm real confused. Are you having a "backfiring" or "afterfiring" condition? The backfire happens in the intake tract, and the afterfire happens in the exhaust.
The .45 caliber shot had to be an afterfire. Very loud and crisp. I haven't decided where the new lower volume pop is. originating
 

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My Vee has a intake pop / backfire every once in a while after a long decel under engine braking then slightly opening the throttle back up. It only happens after the engine is at full operating temp (this is when the stock mapping is the leanest). I have noticed this happening when I first bought the bike (Feb) and continuing on till present day. It has changed in nature as the fuel blend went from winter to summer blend.

I think a stock mapped Vee is very suseptible to fuel formulation change. Gas stations/companies blend their fuel differently from each other for whatever reason and this makes this issue hard to pinpoint.

Mine isn't anywhere near severe enough to make me want to re-map the bike over. I enjoy the great fuel mileage too much.

The afterfiring situation I have no idea about. It is easiest to check the exhaust for leaks when you first start it. They'll be the most audible then and you can get your hands close enough to feel the gases escaping. You can also use a little soapy water in a spray bottle to help you out. Start at the exhaust port and work your way back through every joint (it take the system longer to heat up as you go back).
 
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