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Discussion Starter #1
Ok. So I've had this issue since I bought the bike. Has a leo vince exhause, air filter and a PC3.

Problem is that when accelerating in first gear and ONLY first gear, she'll start to buck at different rpms. I've only heard of the 05 zx6r having problems with second gear jumping so to rule out any problem with the PC3 I zero'd it and she still bucks. I then disconnected the entire PC3 and ran it in stock form and she still bucks. I was thinking that it was a bad map and an ECU ignition/fuel problem but now I'm not so sure anymore. I ordered a set of new shift forks and a drum but wanted to get opinions on here before I start tearing into the bottom end next week.

I can't figure this out. PLEASE someone come up with a viable answer before I sink anymore money into this. Has anyone ever even heard of this happening?
 

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Discussion Starter #3
Think it's a fueling problem? I have access to a computer from an 03, maybe that'll work for testing.
 

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Discussion Starter #4
Reason I thought it was a gear issue was because it still happens with and without the PC3 and just the stock computer both running a stock map... How could they both be wrong?
 

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I don't think it's in your tranny either.

There are many inputs and outputs to you ecu. Removing the PC3 only eliminated it as the culprit. You need to get a proper diagnosis before throwing a bunch of parts at it.

I highly doubt putting shift forks and a drum in will do anything for this problem. If a shift fork is bent or worn down, it would not slide the gear far enough over causing the dogs not to engage in the holes. Or they would not engage far enough and would be spit out. A warn drum will cause the same. It will be in gear or not. The only way it would bounce in and out is if you kept putting it back in gear.

Are you holding your foot on the shifter when the bucking is occurring? If you take your foot off, does it pop out of gear? If not I doubt your problem is even tranny related. Maybe clutch related though.
 

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Discussion Starter #6
I tried holding my foot on the shifter and it still bucks. Nothing is in the way of it fully engaging either. I thought the PC3 bypassed the ECU? Do you think that maybe I should try swapping out for an ECU on ebay? I can't think of any reason why it would only be happening in first gear. I don't think it's the clutch because that really isn't gear specific or fuel/ignition related. I thought it could be the shift forks/shaft and drum because the guy I bought the bike from had a pretty hard fall on the left side.
 

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Discussion Starter #7
So you're saying that if it were the forks, that it would spit it out of gear? I've heard of bikes spitting out of second into neutral, but nothing is below first to spit it out to...
 

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It doesn't go to the next gear down, it goes into "false neutral" basically a position where no gear is engaged.
 

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Discussion Starter #9
It stays in gear, just jumps and bucks. Other than the ECU, what else should I check or just replace?
 

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It's hard to diagnose a vehicle over the Internet. It just doesn't sound like a tranny issue.

I'm sorry I don't have a good direction to point you in other than an experienced bike tech. There are many things it could be. But yes it could be an ecu problem. Could be any sensor deterimining load. Load will also change depending on what gear you are in. For instance you are at much higher load going up hill WOT in 4th than doing just about anything in first.

But not limited to sensors. I'd start with basics. Visual inspection of wiring and vacuum lines. Battery voltage and charging system. Spark plugs, air filter. It could be that because 1st has the hardest pull that something is shorting out from the movement or a vacuum line that is other wise sealed is splitting jus enough to let in metered air in.

Have you searched at all for others with this symptom? I'll keep an eye out and an ear open incase I run across something like what you have.
 

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Discussion Starter #11
I've tried searching a lot for anybody that has first gear issues like mine and the closest thing I came up with was the issues with the forks and second gear. Now that I'm getting more opinions on this, I'm starting to think myself that it's not a transmission issue. I know for a fact that some of my wiring is a little funky. I just changed the battery yesterday when I disconnected the PC3. I wouldn't really mind dropping the $100 for a used ECU. I'm going to have a look at the service manual and see if I can find where some of these sensors might be. I'll try to get a video of it tomorrow. hell, if I get the new ECU, I might as well buy a new wiring harness too and just re-do it all. This is the best 600 I've ever owned or ridden and I'd like to get it back to spec asap.
 

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Discussion Starter #13
The thing is that I don't even need to hammer it in first gear and she'll jump. I could just ease on the throttle and it'll still do it.
 

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Hhhmmm. I'm starting to wonder about the sensor for the counter shaft sprocket. The "speed sensor". I know that's how they calculate what gear your in vs rpm on the newer bikes. Does the speed-o glitch when it's happening?
 

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don't overthink this issue...your problem is most likely the rubber dampers in the rear hub. take it apart & have a quick look...
 

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Discussion Starter #18 (Edited)
don't overthink this issue...your problem is most likely the rubber dampers in the rear hub. take it apart & have a quick look...
Excuse me for asking, but how could anything in the rear hub be gear specific? :confused:

I had the rear wheel off a couple of weeks ago. my alignment is spot on and the chain slack is good. no play in the sprocket.
 

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How would an 05 ecu help you?
 

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Discussion Starter #20 (Edited)
How would an 05 ecu help you?
I figure it was that because a lot of 05 ZX6Rs have had the ECU go through too many heat cycles and their bikes buck and stall. My friend has that same issue. The ECU knows everything that's happening with the bike, speed/gear/rpm/temp ect. I figure that I have the bucking just not the stalling. Since my friend has that issue, I figure that we'll just swap ECUs. if mine bucks and stalls then he'll know that his ECU is fried. If his zx6r just bucks... then I'll know as well.

I just can't think of anything else. A speed sensor is cheap so I'll order one on friday and throw it in. Other than the speed sensor and the ecu... I'm at a loss. I did find ONE other thread about someone having the SAME issue I'm having, but it was from a couple years ago and the thread died with no answer. I did PM him. Hopefully he see's it and replies.

HELP!! My Bike Bucks in 1st. Gear!! : Kawasaki ZX Forums: Kawasaki Ninja Forum

(edit) The 05 ecu won't fix the problem, but it'll rule it out.
 
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