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Old 06-11-2009, 09:44 PM   #1
JG06
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Backfire at Idle, Running very rough

So here is my problem. I was riding home today and could tell the bike wasn't running quite right. Got home, about 10 miles later, and pulled into the drive to hear the bike backfiring. Got off and listened closer, bike was running really rough, idle was down to about 1100 and it was still backfiring.

I pulled the spark plugs and they looked fine, went into town and picked up some new plugs anyways and replaced them, still running like crap and backfiring.

Weird b/c the bike went from running fine to running like crap in about a mile. Wasn't riding through the rain or anything like that.

Mods, Slip-on and K/N filter. Bike has ~22,000 miles on it. Regular oil changes with Amsoil and I know it doesn't need the oil changed. Bike has been ridden hard on the track and street.

To the best of my engine knowledge it has to be something with timing, fuel, or spark. I'm good friends with the mechanic at the local shop and asked if I should have the valves adjusted at 20000 like the manual says but he took the bike for a ride and said it was fine. That's my best guess at this point though, valve adjustment.

If anyone else has had this problem or has any ideas what the problem could be let me know.
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Old 06-12-2009, 01:01 AM   #2
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Re: Backfire at Idle, Running very rough

I would start with electrical connections first and a visual that all the butterflies are working right (SET SDTV)
Does it feel like it is running on 3 cylinders? you were not very specific about why you felt it was not running OK before you got home. Anything more specific will be helpful, like did you get gas right before...etc.
I assume you checked that all sparks are firing.
I know you mentioned a hole bunch of stuff that could be wrong, but it sounds like an A/F ratio in the end. ....unless of course you filled up with diesel
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Old 06-12-2009, 01:09 AM   #3
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Re: Backfire at Idle, Running very rough

+1 to the gas and +1 to the a/f

you didn't put NOS in it did you

Your thoughts sound about right on ZaXos about the A/F. Did you have the bike tuned after the exhaust? Is the exhaust a full or slip?
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Old 06-12-2009, 07:02 AM   #4
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Re: Backfire at Idle, Running very rough

Bad fuel?
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Old 06-12-2009, 11:02 AM   #5
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Re: Backfire at Idle, Running very rough

Exhaust is a slip-on, and it's been on there for about two years. No recent changes have been made to the bike.

It did kind of feel like it was running on three, it's like the fourth one is trying to fire but misses out every time which is what led me to think timing.

It definitely has 91 in it, I filled it up about a week ago and rode it right after I filled it with no problems, so I don't think it's bad gas.

Since it wasn't the plugs I guess it could be one of the coil packs, the bike was my daily ride for the last two years so it got ridden in the rain numerous times, maybe some water is in there causing havoc. I'll go through and check the electrical connections.

Thanks for the tips
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Old 06-12-2009, 11:25 AM   #6
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Re: Backfire at Idle, Running very rough

Coil is a possibility, check the resistance on them and more importantly the connections. I have read of people here discovering a lose connection on plugs, coils and injectors.

Also why 91? the bike is set to run on 87.
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Old 06-12-2009, 12:43 PM   #7
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Re: Backfire at Idle, Running very rough

I'll check the coils, unfortunately I'm in between moving right now so my manual is packed in a box about 2 hours away from here. Could someone post up what the resistance should be?

And I've always run 91 in it, I know they can run fine on 87 but I guess it's just a mental thing for me, it's only about 20 cents more a gallon each time so under a dollar to put in 91 and me not worry about it.
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Old 06-12-2009, 01:02 PM   #8
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Re: Backfire at Idle, Running very rough

Tested the coil packs and they all gave a reading of 1.7ohms. Even without the manual to tell me if this is in range I'm going to assume the coil packs are fine since they all gave the same number.

My best guess now is that it is some sensor that either went bad or is getting a bad connection.
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Old 06-12-2009, 01:36 PM   #9
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Re: Backfire at Idle, Running very rough

if it was a sensor I would expect an FI light. Can you tell from inspecting the plugs which cylinder may not be firing right?

As far as your octane statement, it is more like they are tuned for 87 and yes they can run on 91 but you will lose about 2-3HP. 91 is not cleaner or better gas, it just means that the detonation can happen later in the engine's timing. 91 runs cooler and produces less HP unless you motor is tuned for that with higher compression and different timing.
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Old 06-12-2009, 02:03 PM   #10
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Re: Backfire at Idle, Running very rough

All the spark plugs looked fine and none stood out from the rest. I replaced them about 2000 miles before this with NGK's, stock temp.

I'm going to take it into a shop this afternoon and see if they have any ideas or have any additional diagnostics they can run on it.

Keep the ideas coming though, I'd rather fix it myself then pay someone to.
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Old 06-12-2009, 03:24 PM   #11
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Re: Backfire at Idle, Running very rough

Have you cleaned the air filter? I would check the throttle bodies and make sure they are synced and just look things over in the engine maybe something will stand out
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Old 06-12-2009, 05:23 PM   #12
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Re: Backfire at Idle, Running very rough

Air filter is clean, only a couple thousand miles on it and I looked at it just to make sure. I'm taking it in tomorrow and me and the mechanic will look at it. I'll be sure to let you know what I find out.
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Old 04-20-2013, 04:19 PM   #13
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Re: Backfire at Idle, Running very rough

Quote:
Originally Posted by JG06 View Post
Air filter is clean, only a couple thousand miles on it and I looked at it just to make sure. I'm taking it in tomorrow and me and the mechanic will look at it. I'll be sure to let you know what I find out.
Looking forward to hearing what went bad. I have the same thing going on with my track bike. Ran great all day at the track, last session I hit the rev limited on the back straight and it all went to hell. Same three cylinder style performance. I checked all the coils, I checked each injector, I removed the PCIII and connected everything up factory. I am waiting for new plugs to come in, but these plugs I have in only had one track day on them. Filter is new as well, bike runs equally bad without a filter on the bike. If the plugs don't fix the problem, I guess I'm off to the dealer as well
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Old 04-20-2013, 05:10 PM   #14
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Re: Backfire at Idle, Running very rough

Quote:
Originally Posted by phueter View Post
Looking forward to hearing what went bad. I have the same thing going on with my track bike. Ran great all day at the track, last session I hit the rev limited on the back straight and it all went to hell. Same three cylinder style performance. I checked all the coils, I checked each injector, I removed the PCIII and connected everything up factory. I am waiting for new plugs to come in, but these plugs I have in only had one track day on them. Filter is new as well, bike runs equally bad without a filter on the bike. If the plugs don't fix the problem, I guess I'm off to the dealer as well
I don't think you wait for the answer from OP. It was almost four years ago that he posted.

You should start a new thread with your problem. Just a idea, but have you done a compression test yet? Possible bent valve?
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