Backfire

My 2003 Kawi ZX7R with 4500K miles has got a nasty backfire. It doesn't seem to be gear or RPM related. Every once in a while cruising or accelerating a blue orange flame exits the exhaust and the tach drops to zero for that split second and then it resume to normal until it does it again. (All lights stay on while this happens so I do not think it is electrical)
I am unsure where to start? I checked the air filter and plugs and they seemed ok.
My only other guess is ignition timing.
Any advice would be greatly appreciated.

maybe compression?
or carbs needing a sync and/or cleanup?
the 03 is still carby isn't it?
dunno - ignore me, MadKaw or Smitty or someone is likely to provide a more useful response
ty

my guess...is the kill switch.....
sounds dicky and is cutting off the ignition ...for a moment....

mate ...
you're not riding along with ya thumb resting against the switch are you?????
easy to do....

btw
its an ol' trick....to get a bike to backfire....
flick the kill switch.......

now...who of you have ever dun that..???

Last edited by Smitty on Thu Aug 12, 2004 3:29 pm, edited 1 time in total.

blue orange flame exits the exhaust and the tach drops to zero for that split second

Damn gotta fix that tacho... Can't see anything else being wrong *grins*



In all seriousness, it sounds like an electrical problem.. possibly earth..
Engine stops running, most likely are a point where the Tacho is connected, fuel is still running through the carbs, as it's runing and in gear.
then it's is jump started back up again, and the unburnt fuel moves through the exhaust and is ignited..

Sounds like you need to check a few bolts and stuff.. Sorry I'm not familiar with bike electric so i'm not much use.. Dave??? I'm sure one of the ZX7 guys would have abit of an idea as to where to start..


Good luck.

Welcome mate, I like your choice of bike. But tell me it's a green one, coz we seem to have way too many poofy Black and few too manyRed ones on here. If evrybody only sore green we'd all be happy.
Back fire. My 7 backfires if I close the throttle at 11,000rpm+ and then crack it open again. Thats due to over lap in the valves and stuff. It doesn't loose power at all though. So it sounds like you've got a problem.
If all you lights stay on, your not loosing ignition as such.
but could be;
- A loose earth wire on the coils that will interrupt the circuit from vibration at high revs.
- If there is a dodgey contact in the ignition some where, these simptons can pressent themselves. As the revs build, or the engine is under a haeavy load, any loose connection can cause a break down in the power to the plugs.

A simple problem with air or fuel will USUALLY express it self accros the rev range and consistanly.

Strange question but, does the bike back fire before the tacho drops, or does it back fire and then the needle goes back up. ie, do you actually see the needle drop?
If you loose power to the ignition curcuit the engine will stop firing, and the tacho will die. If you have momentarily opened/moved the throttle while the ignition a was dead, you will/can get a massive backfire once the curcuit is resumed.
When done intentionally, this a great trick for school girls at the nearest bus stop
Have you had any of the electrics out of the bike, or have could you have pinched the wiring loom while putting the fuel tank back on? This is very easily done on the 7.

Don't know if I've understood your question exactly, or if I've just confused you. But stay in touch, it's lots of fun around here.

My bike backfires... When I roll off the throttle and it's a crisp night. A nice blue flame about a foot or two.

Scares the bejeezers out of pedestrians.

Sounds electrical, or some crap in your carbs.
Add to the list of things to check, the sidestand cut off switch..

Good luck..

Thanks for the reply everyone. I am going to look around to see if there is a loose ground somewhere first. Hopefully I get lucky and find the cure tonight. I appreciate everyone with there concerns about my topic. I will fill you guys in when I know more. In the meantime, any other suggestions would be greatly appreciated. Thanks again everyone!

To answer mattyv74 question. Unfortunely the bike is neither black green or red. I say unfortunately because I personally am not a fan of aftermarket paint. The bike is two toned blue and white. Doesn't look bad but not my favorite. Got a great deal on it though so I couldn't pass it up.
Thank again everyone

Welcome aboard.

whatever it is it doesnt sound too good.

As Dave said check the stand switch


mario

yup, turn it off, turn it on then clutch it (at say 80kph) and she blows
flames..looks cool, but not gr8 for ur bike (EFI bikes WONT do it)....
> its an ol' trick....to get a bike to backfire....
> flick the kill switch.......
i was gunna say possibly a carb sync thing, or maybe its running too
lean/too rich?? unburnt fuel igniting in the can..but that doesnt explain
the tacho/ etc....hm
neka



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As others have said I'd probably first check out the side stand switch and go from there, chacing an electrical gremlin is a real pain in the arse!

As others have said I'd probably first check out the side stand switch and go from there, chacing an electrical gremlin is a real pain in the arse!

uummmmm I'd hope he'd have sorted this by now....

I didn't even look at how old this was until I saw posts from Neka!

Timely though... my 7 did something similar recently, except then the ignition fuse blew and blew again and blew some more times until the tank came off and some wires got wiggled and has been fine since. So possibly could have pinched the wiring loom?????????