Mysterious bike problems (won't start, random misfire) - Suzuki GSX-R Motorcycle Forums Gixxer.com
 
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post #1 of 6 (permalink) Old 11-27-2012, 08:28 PM Thread Starter
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Mysterious bike problems (won't start, random misfire)

So here's alittle detail about the bike it's a 2007, bought it use to start right up and die right after. Adjusted the idle to 4000 and after awhile it will drop down and die. I'm not quite sure if I adjusted the cold idle right, but the bike stays on just fine if I keep giving it gas by throttle. But once I let go, it will shut off. Then some mysterious times, it will stay on and run just fine and ride fine until I shut it off and try to start it back up and it will get pissy and shut off.

Then another day comes, I try to start the bike and it will just keep cranking and won't start. So I'm pissed off and I step away for 30 minutes, try to start again and it will start but a loud bang from the exhaust from flooding I guess. And shuts right off after it starts. I watch and I can see the little oval moving where the throttle body cables are and they move just fine.

I tried switching out the tip over sensor, ecu, spark plugs, air box, gas tanks, fuel lines, rectifier. I tried fresh fuel, fuel cleaner, and etc.

I sprayed starter fluid directly into the throttle body and it won't start.

Also when it did finally hold a idle, a continuous extra "poof" will happen like a very mild backfire.

The bike is completely stock no modifications done to it. My friend just stopped riding it for 6 months and let it sit and came back one day and it won't start.

If anyone here can offer some kind of help please feel free to give me some input.
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post #2 of 6 (permalink) Old 11-27-2012, 08:42 PM
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Re: Mysterious bike problems (won't start, random misfire)

sounds like ignition to me. i doubt all 4 of your coils went bad. do you have an filight flash? i know that at one point, i had water in my ecu connector and it really messed up my bike. made i throw all kinds of codes. after i dried it out and sealed it up, no problems ever again.
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post #3 of 6 (permalink) Old 11-28-2012, 08:18 AM
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Re: Mysterious bike problems (won't start, random misfire)

Is it throwing any codes when it won't start? Put in dealer mode and try and start the bike. At least this will tell you if the ECU thinks everything is happy.

Low compression will cause hard starting also. You might want to do a compression check just to get that out of the way.

Another thing might be a big vacuum leak. It will cause hard starting and also will not idle.

Just some thoughts.
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post #4 of 6 (permalink) Old 01-28-2013, 12:21 AM Thread Starter
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Re: Mysterious bike problems (won't start, random misfire)

^ turns out it was a bent valve. how hard is it to repair one?
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post #5 of 6 (permalink) Old 01-28-2013, 07:16 AM
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Re: Mysterious bike problems (won't start, random misfire)

Quote:
Originally Posted by choleaoum View Post
^ turns out it was a bent valve. how hard is it to repair one?
You mean like intake or exhaust valve?
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post #6 of 6 (permalink) Old 01-28-2013, 08:09 AM
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Re: Mysterious bike problems (won't start, random misfire)

Quote:
Originally Posted by choleaoum View Post
^ turns out it was a bent valve. how hard is it to repair one?
It is in the very upper range for a DIY project. If you have good mechanical skills, the service manual and proper tools. Not to be snarky, but if you're asking the question the chances of you getting the engine out, open, repaired and reinstalled are not very good.

Are you sure it is a bent valve? They get bent if the cam timing is wrong or the valve sticks open for some reason. I have not heard of any bent valves on these engines unless someone assembled and timed it wrong and tried to start it. This does not sound like your situation. I'm guessing you have low compression in one cylinder. Was the condition confirmed with a scope?

If it is just sticking open, sometimes some PB Blaster or Marvel Mystery Oil sprayed on the valve stem through the port will get it moving again. If it is bent or burnt, you're done.

Last edited by rv6john; 01-28-2013 at 08:13 AM.
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