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Jumping out of 2nd gear? Pull that engine......

This is a discussion on Jumping out of 2nd gear? Pull that engine...... within the ZX-12R forums, part of the Kawasaki Motorcycles category; My 2000 ZX-12R with 13,000 miles started jumping out of 2nd gear a few weeks ago and got worse and worse until 2nd was basically ...

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Old 07-14-2003, 05:18 AM   #1
Junior Member
Joined: Jul 2003

Posts: 5
Jumping out of 2nd gear? Pull that engine......

My 2000 ZX-12R with 13,000 miles started jumping out of 2nd gear a few weeks ago and got worse and worse until 2nd was basically useless. I rode it too long like that.....At first I thought it was ignition. Cutting out or missing, but it was only in 2nd gear. Took me a while to figure that the problem was with the transmission. Anyway, I tore into it this weekend and wanted to share pictures and what I've learned.

First, I dug into the oil pan from underneath. You must remove the radiator, exhaust, blah blah and then the oil pan. The Kawasaki manual is actually really good about giving step by step intructions. Buying one is a must if you plan to do this. You can change the shift forks and shift drum from underneath pretty easily by going through the oil pan. I was hoping that would be the only problem and I'd be done with it. Not the case.

I got the oil pan off and saw lots of debris. Turns out most of it was gasket type material, but there was also lots of pieces of steel too. Not good. Shift forks and gears are made of steel, by the way. Here's a link to some big digital pictures. They're all about 1 Mb, so I didn't post them here.


I pulled out the shift drum and shift forks. There's one shift fork on the input shaft and 2 on the output shaft. I was skeptical of the fork that engages 2nd gear, and when I took a look at it, sure enough, one side was badly worn. It was ground down and blued from heat. The way this works is that this shift fork actually moves 5th gear side to side. When you want second gear, this shift fork moves 5th gear towards second gear. Each gear has dogs on the side and they lock together. Since this fork was worn down, it didn't push the gears together all the way, and they'd move apart and jump out of gear.

So, now that I knew this fork was in terrible shape, I knew at least 5th gear was in bad shape too. Both pieces had to be badly torn up since they rub on each other. So I knew I had to change at least one gear. To change transmission gears, you need to split the crank case, and to split the crankcase, you have to pull the engine.

So I pull the engine step by step like the manual say. Again the manual was great. It was a little tedious, but much easier than I imagined. I used my home rigged engine stand and flipped the engine upside down. I actually put an old pillow on my work bench, flipped the motor upside down by hand, and set the motor down very gently on the valve cover. Then I straped it in place so it wouldn't fall over and went to work.

I split the crankcase and finally could see all the damage. 2nd gear and 5th gear are toast. The dogs on each gear were rounded off and you could see where they slipped past each other when it jumped out of gear. See the photos in the link above. Also, as I guessed, 5th gear was badly worn where the shift fork rubbed against it. I feel lucky no dogs broke off and took out the rest of the engine.

So far, I have 1 bad shift fork and two bad gears. 2nd and 5th on the ouput shaft. That's where I'm at now. I'll probably replace all 3 shift forks just for fun. I'm also going in for closer inspection of all the gears and bearing and then ordering parts. It's actually not that bad of a job. Lots of little steps so it gets long though.

Question, do I also need to change the 2nd and 5th gears on the input shaft also? They look fine, but putting a new gear in that meshes with a used gear seems like a bad idea.

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Old 07-14-2003, 05:25 AM   #2
Senior Member
From: NC
Joined: May 2002

I Ride: No bike

Posts: 12,494
Welcome Mark....

Thats an impressive first post :D

I have to go back and read it again when I have a little more time ....
Old 07-14-2003, 05:39 AM   #3
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From: NY,NY So Nice They Named It Twice
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Posts: 4,208
Welcome aboard.....and an expensive post at that .......

Old 07-14-2003, 06:13 AM   #4
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Black Mandingo Warrior's Avatar
From: Dayton OH
Joined: Mar 2002

Posts: 142
Check The Shift Drum Too!!

If your forks are that badly worn, chances are the shift drum has unacceptable wear as well. Look at the shift fork buttons that slide through the shift fork veins and the veins as well carefully. If they are the least bit scarred, you'll have problems. I did the transmission work on my 95 9R and the drum was bad as well (similar symptoms). If the dogs or holes in the opposite gears look good they should be alright. I've heard where some folks have had the dogs backcut on an angle to help pull the gears together and making it less likely to jump out of gear. Also inspect the cases where the outer shaft bearings are seated. If the cases are like my 9's one side will have a dowel pin to position and secure the bearing, the other side will have a "C" type clip that rides in a groove in the gearing and case. On my 9 the clip somehow slid around to the side of the case without the groove and cause the bearing to move enough for the bike to jump out of gear. Best of success to you and your rebuild.

Old 07-14-2003, 08:43 AM   #5
Senior Member
From: Arlington, TX
Joined: Apr 2003

Posts: 170
i just went through the same situation about 3 weeks ago.

I had 2nd and 5th input, along with two bent shift forks, 3rd & 4th input, 1st input, 1st output, shiftdrum.

i think somebody on here was selling a complete tranny for fairly cheap. you may want to look in the for sale area. may come out ALOT cheaper for you.

Old 07-14-2003, 08:45 AM   #6
Junior Member
Joined: Jul 2003

Posts: 5
It's not actually my first post. I used to post under BIGCC. I mostly read and don't post. But I couldn't find much info on this topic and decided to contribute what I could.

I'm going to check out the shift drum for sure too. It seemed to be in spec., but I can't imagine it's not screwed up from my jumping out of gear action.

Also, what do you think about replacing my crank bearings while I'm there. Is that easy or even necessary?

I'll check out the bearing c-clips for sure. Thanks.
Old 07-14-2003, 08:54 AM   #7
Senior Member
From: Destin, Florida
Joined: Jun 2002

Posts: 1,336
I would strongly recommend having the dogs undercut while you have it out. Makes it a lot less likely you will ever have this problem again.
Old 07-14-2003, 09:00 AM   #8
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GO 200's Avatar
From: Cadiz, KY USA
Joined: Sep 2002

I Ride: 2000 ZX-12R

Posts: 25,285
Mark4 - Great post!! Keep up the input so this thread can be archived!! That way, there will be info there for the next guy!! Thanks for the info!!

:shock: :shock: There's nothing quite like opening up the cases & seeing GEARBURGER WITH METALFLAKE GRAVY!!!!!!!!! :shock: :shock:
Old 07-14-2003, 10:23 AM   #9
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From: bristol,,uk
Joined: Feb 2003

Posts: 126
keep up the good work and keep us posted plxs..
Old 07-14-2003, 10:35 AM   #10
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From: West Of The Mississippi
Joined: Nov 2001

Posts: 7,910
I'll have to join imagestation tonight so I can read, but this looks like an excellent thread. :D
Old 07-14-2003, 11:07 AM   #11
Junior Member
From: az, usa
Joined: Jul 2003

Posts: 3
iam thinking about getting a 03 zx12 are there problems like that with new ones. What about other things
Old 07-14-2003, 11:16 AM   #12
From: Stoke - UK
Joined: Oct 2002

Posts: 93
First of all sorry about people suffering from various gearbox/engine probs

Is this something alot 12 owners can look forward to? :cry: :cry:

Seems to be a few too many cases for my liking :(

Hope you manage to get them fixed soon

Old 07-14-2003, 11:26 AM   #13
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Avenger's Avatar
From: Elyria, Ohio
Joined: Feb 2002

I Ride: 2001 ZX12R

Posts: 3,409
Mark ...first off welcome to the POSTING part of the board...lol....Secondly, thats one hell of a post, THIS THREAD SHOULD BE ARCHIVED WITH THE PICS........Epstien this is your first major project as moderator man !!! Do us right, and make sure you get the pics !!

Thanks Mark
Old 07-14-2003, 12:14 PM   #14
Junior Member
Joined: Jul 2003

Posts: 5
In case anyone is wondering about what I have done to my bike and how I've abused it, I have full Akrapovic exhaust, PCIIIR and K&N's. Dyno'd at 178 rwhp. Not what I would call outrageous power. I've been to the drag strip 3-4 times, 2 track schools(days total), and lots of pud wheelies. I think it all started from missing 1-2 full throttle upshifts. I don't miss many, but I'm assuming that's what started it. There's people with lots more power and many more drag strip passes that still have an intact transmission. I'm not completely sure what caused this particular problem.

I'll put more pics in the imagestation photo album as I dig deeper. I'll be sure to put one up showing the worn shift fork next to a good one.

Old 07-14-2003, 01:06 PM   #15
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Black Mandingo Warrior's Avatar
From: Dayton OH
Joined: Mar 2002

Posts: 142
I'll post photos from my 9R tranny operation, they look about the same. I think I have some photos of the damaged parts.

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