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Discussion Starter #1
My 06 backfires badly when upshifting ( almost without fail from 1 to 2 and a lot less from 3 up)
I have a power commander on the bike-could it be that it needs to be re mapped ? The charge to put the bike on the
dyno is $350-a tad bit expensive. Is there anything else I can look at that may be causing this problem ?
I have no idea as to when plugs etc were last changed on the bike.
 

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Does it also backfire if you rev it up in one gear, and then throttle off to compression brake?

If it backfires when you compression brake, does it stop if you crack the throttle open just a bit?

If the bike is only backfiring when you upshift, it might be your timing between the throttle and clutch, if you are shutting the throttle off just before you clutch in, or just after

another possibility: maybe you are reving up almost to the point of hitting the rev limiter, then when you pull the clutch in the engine jumps higher, and the limiter kills the spark, flooding the exhaust with gas.
 

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Discussion Starter #3
Thanks for those points KCW-the answer is "no" to both your first and second questions. I'll try shifting from 1 to 2 quicker and see
what happens.
 

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another question for clarification: is the bike sounding off one loud BANG! like a gunshot or is it sputtering and popping

backfiring is a very generic term

on my V4 royal star when I accelerate hard and shift fast the bike makes a noticeable BROWGH sound everytime I upshift. If I intentionally throttle off and then shift it doesnt make that sound

The RS and my VS650 both pop and crackle when I compression brake unless I crack the throttle a bit.

I have seen a harley with loud exhaust go by and do the shotgun blast with a bright flash out the muffler everytime he shifted. (it was nighttime). I dont know if he had set up the bike to do that intentionally? If it was my ride it would drive me nuts.

When I had air cooled VWs I discovered if I took my foot off the gas at 40mph in 3rd gear, turned the ignition (key) off, pumped the gas quick, then turn the key back on it would backfire like a shotgun.

I thought it was great... until I blew a $100 aftermarket muffler in half, split it right open.
 

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Discussion Starter #5
Took the bike for a ride yesterday-tried shifting shorter ( shifted up to 2 very shortly after take off) and bike didnt backfire. To answer
your question the bike was sounding like a gunshot when shifting longer. Seems like the shorter shifting sorts the problem. I drove around for ages to to try and get the bike to make a BROWGH sound but no luck lol !! anyway KCW thanks for the input-much appreciated.
 

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I did experience some back firing before the stator in my 2014 Vstar 650 failed. Not being a mechanic I can't really provide further details. Not sure if this is appropriate to your issue or not.
-PH
 

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Maybe check your gas as well. When I first got my 2010 Strat, I was using premium like the dealer said, but I would sometimes get it at grocery store gas stations or anywhere else I could find it cheap. I used to get a single, loud gunshot blast backfire when I'd upshift. Having not put 2+2 together I stopped in and asked the mechanic at the dealership about it and he asked where I was getting it. When I told him he told me to stick with stations that only sell top tier gas like Shell & BP. I did and haven't had an issue since.

Good Luck ... Ride On!
 

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I had the same problem and overcome it by fitting a Memjet remapping device. It cost me a couple of hundred but totally solved the problem plus gave me more power and better fuel consumption. It simply plugs into your Air flow sensor and has a dial from 0 to 9. Mine runs best set on 8 when its cold weather and 5 in summer. I bought it in eBay last year.
 

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Another cause of some backfiring/popping noise when downshifting etc...is valve clearance. Have you ever had them checked?
 

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I have a power power commander on the bike-could it be that it needs to be re mapped ?
Have you tried going to the power commander site and getting the recommended map? You can download the software and the map. Using USB and a laptop you can re-map yourself.

Popping and backfire is a lean condition. I pulled the power commander off mine to get better MPG but now have the popping factory lean condition when off the throttle and slowing down.
 

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I had a very similar problem with my Roadliner. Could not figure it out. Stock bike. Started to miss a bit and backfire. By the way the Dealer was NO help at all. Tried everything that is typical, gas, air restriction, vacuum line leak etc. I was almost ready to give up. Then decided to change plugs as last resort as they are not easy to get to, especially the rear ones. Upon taking out one of the rear plugs I found that it was not in very tight at all, just a bit more than hand tight. All the other plugs took significant force to break them loose. This one did not, easy to get loose. Anyway put in all 4 new plugs and snugged them all up real good.
Started the bike up and it ran ‘PERFECT’ no misfire, no backfire or anything. I believe the loose plug was letting in extra ‘air’ during the ignition stroke thereby causing partial misfire and backfiring on occasion. That is the only thing that makes logical sense. Anyway that is what solved my problem. If I were you I would change all 4 plugs, paying close attention as to how tight they are currently in place in the bike. If you have one or more not that tight, that could be your problem, same as mine. Good Luck.
 

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^ that was a good catch - the cause of a backfire is almost always a dirty carb or injector that is running lean, or a vacuum leak.

No one ever thinks "hey maybe my sparkplugs are loose, or the head bolts are not torqued, or any other the other 100 things an engine needs to be correct to run like its suppose to.

When I got my Royal Star it ran terribly, and I thought it was because the previous owner only rode it once a year for the last 2 years (to get it inspected) I was chasing old gas problems, running seafoam thru the tank, changed the air filter... and then decided to pull the plugs, look at them, and replace them.

all four were only finger tight.

Ursa runs like a dream now.

Have to add: get a torque wrench - there are two threads that frequently get stripped out on motorcycles: the spark plugs, and the oil drain plug. Even a $10 on-sale chinese torque wrench from Harbor Freight is better than tightening steel bolts and plugs into aluminum by feel.
 
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