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Sup e'rbody. New to this forum, and I also just bought my first bike. Just brought it home tonight, and its an '03 800 Boulevard Volusia. Its used of course, and trouble is, upon driving it home, it backfires like a SOB when decelerating. Dude I bought it from said its tuned rich, and carbs have been jetted for aftermarket Cobra pipes, but it backfires really bad. He said it should clear up when it warms up, but it didn't, and I've already bought the damn thing now. Its a great looking bike and sound great too, except for the backfiring problem. Any ideas on what to do to keep from happening, as I'm really new to all this. Thanks
 

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First post needs a hearty welcome....Hearty welcome from the Burg'
Congrats on the older Vol, any pixs?
Does these said Cobras have original Baffles still in???
 

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had a similar problem on my 06 c90 when I bought it back in 2014...difference between yours and mine aside from it being a 800 vs a 1500 is that your 03 is carbed vs mine which is fuel injection...fellow rider suggested to cure my problem I look into the GMan Bully...so I did and also replaced the stock air filter...which the previous owner should have done when he changed the pipes... with a K&N...problem gone. Good company to deal with...good customer service. Good luck.

 

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Thanks for the replies, and also for the hearty welcome @duglaura. Far as I know, it has stock intake @scorpion46. As far as your reply @DCatCt, I may have to try that. New rider here, and plan on upgrading when time permits, but gonna keep it small for now. All in all tho, I must say I went a little beast mode when I brought it home last night. Went to pick it up with my nephew about 15 miles from home, and it snowed like a b#$!* here in Louisville on the way. Snow stopped after we got there, and was cold as hell, but I saddled up with some winter gear and drove her home anyway. Was nervous as hell at first, but drove her home anyway, slow and low, but opened her up a few times close to home. I grew up on dirt bikes, but its my first street bike at 45 yo. Anyway, I'm dedicated to making it right. Have also seen some posts, and talked to Suzuki service provider here in Louisville today, who suggested blocking the secondary. After researching a little, I'm guessing he was referring to the pair valve. Any ideas on that? And thanks again for ya'll's replies.
 

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I have an 04 Volusia that was doing this shortly after I had bought it, put about 6k miles on it running perfect then developed a hugh back fire. I de-paired it, gone, been 2yrs never came back. It may work for you it may not, but it did for me. Should be able to find the procedure on this forum or on youtube, easy to do Just a suggestion if all else fails.
 

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This comes up all the time. Can we have a sticky about it so people can find the info readily?

The PAIR valve injects air into the exhaust to make sure any unburnt fuel gets burnt there. It’s not harmful and the popping sound is common on all kinds of bikes. If you remove the PAIR valve you will likely have less of an issue but it might not go away entirely. If the popping bothers you, rejet or if you really must remove the PAIR valve or disable it. If you are like me and like the popping, it’s fine and does no harm. In fact it does good things for the planet so just think that every pop is you saving a polar bear’s dick from breaking off (look it up, this is a real problem stemming from global warming).

If your noise is not popping, it could be a backfire. The way you tell the difference is that a backfire sounds like a gunshot and is just as loud. That happens when you suddenly have way too much fuel and it ignites in the exhaust. You can do all manner of things to cause it like “key banging” but I don’t believe backfires are a common problem on these bikes. You could also experience a backfire that goes the other way, through the carb. I have caused this when manually choking the bike (literally putting my hand over the carb intake with the air box and plumbing completely removed. This is normally super uncommon.

So question one: was it a true backfire? If so, diagnose it like one. Check that you get consistent strong spark as that would be the most obvious cause. If that’s not it, keep researching.

If it is a deceleration pop, either don’t worry or rejet. Rejetting fixes it because paradoxically when a bike runs lean it runs hotter, so the exhaust is hotter and despite running lean you won’t ever burn all the fuel in the combustion chamber (six stroke engines can do that I believe but as far as I know nobody has ever put one on a motorcycle). So you get very hot unburnt fuel in the exhaust and the PAIR valve injects oxygen rich air to help it self ignite. By going one size up on your idle jet you can stop this from happening or at least mute it because richer mixture means lower temp means less self ignition in the exhaust. I did this on my otherwise stock bike and while the popping didn’t go away, it is at least 10dB quieter (twice as quiet) and requires a lot harder deceleration to start.

You said your bike has Cobra pipes. This might make the popping louder, I don’t know. You said the previous owner said it was jetted rich. That’s not really what you want. I wouldn’t trust them. Is the bike stock otherwise? As in, any modifications to the air intake, filter, etc? If it is stock or uses just a K&N filter, go to the Rejet Matrix thread and get the correct sized jets and needle for your setup. Clean the carbs while you are at it, and it’ll work just right. If it’s a really custom setup, bring it as close to stock as you can, then start jetting from there. Get it to run well, then make changes one step at a time. Worst case, go get it on a dyno and have them figure out what jets you need.
 

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This comes up all the time. Can we have a sticky about it so people can find the info readily?

The PAIR valve injects air into the exhaust to make sure any unburnt fuel gets burnt there. It’s not harmful and the popping sound is common on all kinds of bikes. If you remove the PAIR valve you will likely have less of an issue but it might not go away entirely. If the popping bothers you, rejet or if you really must remove the PAIR valve or disable it. If you are like me and like the popping, it’s fine and does no harm. In fact it does good things for the planet so just think that every pop is you saving a polar bear’s dick from breaking off (look it up, this is a real problem stemming from global warming).

If your noise is not popping, it could be a backfire. The way you tell the difference is that a backfire sounds like a gunshot and is just as loud. That happens when you suddenly have way too much fuel and it ignites in the exhaust. You can do all manner of things to cause it like “key banging” but I don’t believe backfires are a common problem on these bikes. You could also experience a backfire that goes the other way, through the carb. I have caused this when manually choking the bike (literally putting my hand over the carb intake with the air box and plumbing completely removed. This is normally super uncommon.

So question one: was it a true backfire? If so, diagnose it like one. Check that you get consistent strong spark as that would be the most obvious cause. If that’s not it, keep researching.

If it is a deceleration pop, either don’t worry or rejet. Rejetting fixes it because paradoxically when a bike runs lean it runs hotter, so the exhaust is hotter and despite running lean you won’t ever burn all the fuel in the combustion chamber (six stroke engines can do that I believe but as far as I know nobody has ever put one on a motorcycle). So you get very hot unburnt fuel in the exhaust and the PAIR valve injects oxygen rich air to help it self ignite. By going one size up on your idle jet you can stop this from happening or at least mute it because richer mixture means lower temp means less self ignition in the exhaust. I did this on my otherwise stock bike and while the popping didn’t go away, it is at least 10dB quieter (twice as quiet) and requires a lot harder deceleration to start.

You said your bike has Cobra pipes. This might make the popping louder, I don’t know. You said the previous owner said it was jetted rich. That’s not really what you want. I wouldn’t trust them. Is the bike stock otherwise? As in, any modifications to the air intake, filter, etc? If it is stock or uses just a K&N filter, go to the Rejet Matrix thread and get the correct sized jets and needle for your setup. Clean the carbs while you are at it, and it’ll work just right. If it’s a really custom setup, bring it as close to stock as you can, then start jetting from there. Get it to run well, then make changes one step at a time. Worst case, go get it on a dyno and have them figure out what jets you need.
I agree with this. Every bike I ever had- I removed the pair valve or air induction into the exhaust. This will eliminate or almost eliminate popping on decel. It sounds like your problem. (Correction- I never removed it from my c-50. Maybe next winter it could be a fun project!).
 
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