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07 GSXR 750 Missing at 10500 rpm


donkason

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Her is the rundown. Got my track bike with 3300 miles and bone stock but it had a slip on. It had a flat spot about 7500-8500 rpm range. It wasn't a miss, but more of a bog. I bought a PCIII and had it dyno tuned at Pegrams. The guy said the III only works the lower injectors and doesn't help with the top end rpm range. He tunes it the best he could and it has done okay so far.

The last few track days a miss, not a bog, has been developing at 10,500 rpm. It was getting bad Monday. It was fine up to that range and then after maybe 11500 it took off like a scalded dog to the redline. I run pump fuel 93 octane and I haven't changed the plugs. It has around 6000 miles on it now. I threw a gallon of 100 octane in there to see what it did just for the hell of it and it got horrible. I was launching out of corners past people and losing the pass because it was spitting so bad.

I'm going to clean the fuel filter in the pump and I was thinking about other things that may cause this. My first idea was to get a new fuel management system that auto tunes all 8 injectors but that's gonna be 5 bills and I want to troubleshoot before I drop the coin.

Any suggestions on what to do or where to start?

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You can try running 87 but I wouldn't, it calls for 93 octane completely stock.  I'd remove the PCIII and see if it still happens, seen them go bad from time to time.  I'd do the cursory check on the connections for the injectors, as well as the TPS and anything else touched by the PCIII.  I'd also check the coils to make sure they're seated and connected securely.  And it'd be a long shot but check your battery and stator.  I had a bad battery cause me problems before where the bike would feel like it was cutting out.

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Her is the rundown. Got my track bike with 3300 miles and bone stock but it had a slip on. It had a flat spot about 7500-8500 rpm range. It wasn't a miss, but more of a bog. I bought a PCIII and had it dyno tuned at Pegrams. The guy said the III only works the lower injectors and doesn't help with the top end rpm range. He tunes it the best he could and it has done okay so far.

The last few track days a miss, not a bog, has been developing at 10,500 rpm. It was getting bad Monday. It was fine up to that range and then after maybe 11500 it took off like a scalded dog to the redline. I run pump fuel 93 octane and I haven't changed the plugs. It has around 6000 miles on it now. I threw a gallon of 100 octane in there to see what it did just for the hell of it and it got horrible. I was launching out of corners past people and losing the pass because it was spitting so bad.

I'm going to clean the fuel filter in the pump and I was thinking about other things that may cause this. My first idea was to get a new fuel management system that auto tunes all 8 injectors but that's gonna be 5 bills and I want to troubleshoot before I drop the coin.

Any suggestions on what to do or where to start?

i had an 07 gsxr 750 - like they said unhook the PCIII, also check your fuel filter - that might be the cause, i cleaned mine last year it was dirty as fuck, also check your battery if voltage is low when your high up in the RPM's it demands more power, if the battery is falling on its ass that could also be the issue, what plugs ru running? Have u ever checked them?

Edited by silentcropduster
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Great info! I don't think I got a bad tune because the bike ran well after and now a problem pops up in a different spot.

I just replaced the battery last track day so it should be good to go.

I'll clean the filter and I'm going to swap the plugs for starters. Then try it out. If it's still there I'll disconnect the PCIII and see how it goes.

You guys are the cars meow!

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1) Battery will cause the issue you speak of, it is somewhat common

2) Dyno Brian will tune your bike better than any other in the area, yes he knows more about tuning bikes than Pegram

3) Yes it only controls 4 of the 8 injectors, the primary injectors. It does not control the secondary injectors and does not need to unless you have a highly modded motor requiring more fuel than the primaries can provide. Him telling you its the best he can do with only 4 means he is not on top of his game in engine tuning, you dont need to control them.

 

Replace battery and have Brian retune it, thank me after.

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If my plugs and filter don't fix it I'll head to this DTM gentleman. Where is this mystical dyno man that everybody speaks about. I've never heard a bad thing about him so might as well try it.

I ran a 1:45.94 with the bike falling on its nose out of every turn. It'll be worth the dough to see what I can do when it's on point!

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Cleaned fuel filter. It wasn't really dirty at all. Then I went to change the plugs and have a dumb question. The old ones that came out had a threaded top and the new ones have a fitting on the top. I pulled two old plugs and both had threaded tops only. Are they supposed to be threaded or did something come loose and get stuck in the plug boot?

I took the threaded old plugs and tried to screw them back into the boot to see if there was something in there I could snag and drag out to no avail. I just want to check before I slap it all back together. Thanks!

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