Oh...Excuse Me!  No that was a backfire!


So... lately the ride has been doing a backfire thing...I'll come off the gas in almost any gear and I get a backfire. I understand what's happening but I'm alittle concerend that it's just starting to do this...@9k.

Could this just be spark plugs?
No engine mods at all..Stock pipes, and gearing.

Elevation? I dunno a hundred over sea level I guess. But doesn't the Fi compensate for altitude changes?
i get tons of backfire when off the gas real quick and a few thousand rpms high
i think my valves need shimming tho
I have been having a "sputtering" sound when a low speeds
(keeping a steady speed? )
so far the only preformance mod I have done is a yoshi slip-on...
do I need to do any thing else to correct?
I just had my Busa supertuned by a performance shop here in the DC Metro. The bike backfires like a howitzer off idle as a result of the lean jetting. I've been told that the detonation is common on highly tuned rides with lean jetting/carburation the hardened pistons and cylinder heads typical of Suzuki motorcycles should be able to take it, check out the spitting backfire of a formula 1 car for a comparison.

If you are getting good gas mileage and performance don't worry about it. If questionable examine the spark plugs for excessive damage and if that is evident consider a leakdown/compression test for other vacuum trouble.

Even my old GS 1100G started doing it after I had it re-jetted and it wasn't fuel injected.
I'm surprized this is happening with a stock bike, You should check with your dealer or a very knowedgable mech. Mine didnt start doin it til I installed my full exhaust system. It got much better (allmost gone) when I installed my home made TRE and a fuel inj box from techlusion $140 cheaper than the yosh or the PC3 but not as good I think. But sometimes still pops above 4K ft elevation.

- Next thought, for the techies, enginers, trained mech's ...

I have had some mech tell me its running too lean - others its too rich. It has been my opinion that back fire occurs when too rich because :
1 - I can smell it.
2 - My theory is unburned gas seeps into the header and exhaust then exploads from hot pipe.
I have experienced this with vehicles other than my Busa and these are some of the conclusions I have ... can anyone confirm or correct me??? Thanx - Kent
3 - Plus when timing is off spark and gas mixed when valves are open and should be closed...
I changed out the spark plugs this weekend thinkng i was gettig the pops due to unburned fuel. I thought it had made some difference Until this morning on the the way to work. A huge backfire (scared the lady int he minivan next to me).

So it's still happening, just a littel bit less. I'm not sure how to check the timing, I'll have to look into that.

The plugs looked fine when I pulled them out, not the 'gray/white' of lean and not covered in carbon like rich. Could be I'm not consistently getting enough air into the mix, maybe a new filter?
You are probably right Darkeyce, Is that the original air filter? A clogged filter will richen up the fuel mix. Some of that will collect in the headers and cans until - Boom! Try the BMC race or K&N filter. That will lean you out a lot.

Oh yeah, Are you running a Power Commander or did you remap the ECU? That will richen up the mix too. If not you might want to check your timing (cam position sensor, Crank position sensor, etc.) If those sensors are good and adjusted then it might be the timing chain tensioner is slack causing the timing to change and backfire on deceleration. Check the fuel/air mix side of it first though.
This is a VERY serious problem that should not be taken lightly!! I know first hand! I'm going to give you alittle history on my busa. I bought the bike in New Mexico elevation eh...about 5k feet. No problems with back fire whatsoever at this time, back in 2000. Once I moved to Okinawa Japan where I was about 10 feet above sea level I've gotten massive backfires!! The mechanic told me to becareful and not to ride it too hard cuz it going to mess your engine up...this was in Feb of 2002 or so. I was like yeah whatever that blue flame is lovely. Kept riding it...about November time frame he said he knows what the problem is...get the Block off Plates that cost about $40 bucks to solve your backfire problems. I ordered them...but didn't install them. In January of 2003...two up racing through the streets of Okinawa...one hell of a back fire happened. And I heard the strangest sound afterwards...like a nasty grinding sound. Needless to say my engine was toast! Crank, bearings, pistons, head gasket, and hell of alot of other things. I'd say around $4k of damage if I was putting all stock parts back in...but I figured might as well do it right. Everything pretty much after market being replaced. And I'm still working on this damn bike now. We about $6.2k in repairs and replacements.

So I'm going to tell you like this...get the Block Off Plates to end your backfiring! And do it quickly! Only $40 dollars can save you thousands!
my gut feeling from the start of this thread is the pair valve.
i have full titanium exhaust and was warned to do the pair valve mod right away to prevent backfiring. Mine did not backfire so I didn't do the mod... yet (even tho the parts are sitting on my microwave just waiting).

The Pair valve introduces fresh air into the exhaust system for a 'cleaner' emission. Hmm.... extra OXYGEN mixes with any unburned fuel.... Hmmmm..... what do you expect to happen?!! BOOM!

what happens during a huge backfire is a large explosion in the header pipes. if this happens at the wrong time - during exhaust stroke when a piston is going up with the exhaust valve open, the explosion from the header creates so much pressure on top of the piston, you may as well shove a rock in there. Therefore, breaking rods, bearings, crank, etc.

If your bike backfires alot or even just once in a while, fix it before it fixes your bank account!

thanx big FatSac for being the first to mention the pair valve!