Gearbox Trials & Tribulations

Photo's are here

I have been having problems with Sanji's gearbox for quite some time now.

In 1996 it started making strange noises in 4th & 6th, like an occasional rattle or scraping sound. A few months later it starts dropping out of 4th occasionally while under power, and eventually I started riding around it as it got worse. The GTR1000 is so torquey that shifting from 3rd to 5th is easy.

I put off doing something about it for a little too long, and on my way back from the 1997 Bol D'Or race in the south of France, the gearbox first refused to select 6th on the freeway @ 80Mph, and after a 30 minute 40Mph limp into Lyon, France it selected 3rd & 4th simultaneously and locked the rear wheel solid, luckily at only 5Mph.

I called for a tow, somehow realising that this wasn't a "fix it at the side of the road" job. The bike was trailered to the local recovery depot, where I left her to be shipped home, picked up a rental car, and drove home.

At this point I feel I have to mention how hard it is to move a GTR1000 with the rear wheel locked solid. At the recovery depot we lifted her back end off of the ground with a forklift. It was much easier than getting it onto the trailer!

She arrived back in the UK 3 weeks after I did and after a couple more weeks I finally got down to the business of the rebuild.

Gearbox Rebuild #1

It took myself & Phil almost 3 days to get the motor out of the frame.

The initial stripdown took 3 hours, and the rest of the time was spent trying to remove the lower rear engine bolt. This was THE most stubborn bolt I have ever had the misfortune to have to remove. It was fitted by Kawasaki in early 1986 and had stayed put until October 1997.

We tried everything. We sprayed it with penetrating oil and left it overnight. Wouldn't budge! We hit it with big hammers, we drilled into the back of the mounts, and sprayed more penetrating oil into the hole. Wouldn't budge! We heated the crankcase and hammered the living crap out of the bolt. Wouldn't budge!

We went to the Pub in utter frustration and drowned our sorrows.

The following day (mildly hungover) we got some freeze spray, put a gas fire under the crankcase for 30 minutes, sprayed the bolt with the freeze spray, and hammered the almighty living daylights out of it,............. and it MOVED!

Only a ½" or so,..... but it MOVED.

3 hours later we finally had it out (the bolt that is!).

The aluminium of the crankcase had corroded so badly that it was all but welded to the bolt. The bolt went straight (ok, it was a bit bent) into the trash.

Finally the motor was out, and 2 hours later the horrors of the gearbox were revealed. 3rd, 4th, & 6th gears were missing several teeth on both input & output, and there was shrapnel everywhere. After more careful disassembly & inspection we found the reason for the damage. The circlip that holds 4th output in place is in 2 pieces in the sump, and the shrapnel resulting from selecting gears simultaneously destroyed everything else.

Miracle of miracles, the damage was contained to the gears, so after placing an order for 5 new cogs (3rd & 4th are one piece on the input shaft), sundry circlips, spacers, and 3 new shift forks, I proceeded to painstakingly clean all of the bits out of the motor.

3 weeks later the parts arrive and it's reassembly time. This goes pretty smoothly except that one of the spacers was too thick and had to have ½mm ground away courtesy of Phil's place of work. We spend a weekend getting everything right, replacing 2 stretched 6mm crankcase bolts, and one snapped one (luckily the stub came out reasonably easily). Another day saw the motor back in the bike, all the other stuff (cooling system, swingarm, carbs, etc) re-attached, and coolant & oil added. The motor started, and we had 6 functional gears, so we finished re-assembly (plastic, etc) and off I went for a test run.

Despite checking everything carefully she was still dropping out of 4th, and still making those noises in 6th. We'd had enough and I decided to carry on riding her as she was until I had raised enough enthousiasm for another go at it.

Gearbox Rebuild #2

September 1998 came around (as it does) and I had finally raised enough gumption for a retry, besides which I was heartily sick and tired of worrying about it detonating again.

This time the motor came out relatively easily, and by the end of the first day I had the gearbox in pieces. A minute inspection revealed that the shift drum was worn where it selected 4th , and it had some other damage (chipping) elsewhere, so I ordered a new shift drum, and waited the obligatory 3 weeks.

Fortunately, after 1 week, a fellow GTR owner (a shiny 1998 model) approached me to see if myself & another GTR owner (a well abused 1987) would be interested in buying a 1988 GTR that was in bits,.... for £300 ($500). We leapt at the chance, and once it arrived we stripped the gearbox down, and used the shiftdrum out of it to rebuild mine.

After re-assembly the bloody thing was better (no more noises in 6th) but was STILL dropping out in 4th. This is the point at which I came close to finding a rag and a match and burning the bloody bike, but common sense prevailed, and I started saving enthousiasm once more.

Gearbox Rebuild #3

May 1999, and after a trouble free trip to the GTR Day in Holland, I was ready for Round 3. Out with the motor (we're getting good at this now), split the crankcase, and lift the entire gearbox out; clutch basket, shift forks, the whole kit & kaboodle (what is a kaboodle??).

Replaced it with the entire gearbox from the donor '88 bike.

At this point we noticed that one of the set rings that hold the shafts in place is badly worn, so we replace that too, and I fit the brand new shift drum that I'd bought for rebuild #2.

Re-assemble the motor (haven't we been here before?), refit the motor, re-attach the other essentials, coolant, oil, and start her up.

BLOODY thing won't even select 1st. Only neutral and 2nd. Nothing else! I give up in disgust and go home, muttering about loans and new bikes.

During the following week I get a phone call from Phil. Seems he had a brainstorm, and went out and removed the output bevel box, and found that I had badly assembled one of the sprung arms on the external shift mechanism, trapping the arm in place.

The following saturday, we re-assembled what Phil had taken off, and tested the gearbox. 6 gears & neutral, all there, all functioning, so with the minimal amount of bodywork, I take her for a quick run up the hill.

1st - 2nd - 3rd - 4th,................... still in 4th,..... hasn't dropped out yet,....... YIPPEEEEEE!

I leisurely re-assemble the rest of the bike, and after some careful checking take her out for a true test ride. This ride was one of the finest I have taken in a long time (the best part of 3 years) and even though it lasted only 30 minutes it was NIRVANA! The whole bike felt complete again. I could thrash it mercilessly without wondering if it would drop out of 4th, or worrying about sundry noises (there were none!).

The following day I replaced my fork seals, put 380cc of 20W fork oil in each leg, and took her out for a longer run.


This is as sweet as she's been since I first bought her in March 1994.

I am a happy fellow!


Phil 'The Hippy' Chapman who apart from expert help, the use of his garden, garage, and tools, calm advice and provision of cooked meals, is an expert "Kibbitzer" and a very good friend. Thanks Phil. Next up is rebuilding your Z900 and getting the 400-4 on the road.

Terry 'OldFart' Lee, Gary 'Shortarse' Rees, Phils friend Ian, and Big Lee for the muscle, tools, advice, and humour.

The people on the COG listserver, who provided much needed advice, and an audience for my confused meanderings.

'Sanji', for putting up with my botched repairs, violent mistreatment, threats, and outright abuse. I swear I'll be good from now on,........ well,..... better than I have been anyway.

What I learned;

Put copper grease on every bolt when you put it back in.

Replace all the 6mm crankcase bolts with new ones. Standard ones are made from low grade chocolate.

Take your time, check your work at every stage.

Botched repairs WILL come back to haunt you. Do it right the first time.

If you start getting frustrated, walk away and don't come back until you've calmed down.

My advice to you;

Remove, copper grease, and replace your rear lower engine bolt now, before it's too late. It takes 5 minutes, and could save you days of hassle in the future.


When commenting on my gearbox problems on the COG listserver a month or so after the 3rd rebuild, I got an email from Bob Ray COG#95 who had had exactly the same problems as me with his old '86. He has had the problem on 2 different motors in the same bike.

It seems that the outer casing of the bearing on the output shaft of the gearbox is rotating, and wearing away the crankcase and the set ring.

This is what was causing the original problems. My gearbox(es) were fine, it was just this worn set ring.

This seems to be a problem with occasional Kawasaki gearboxes (I now know of a GPZ1100 and a GPZ600 that have also had it) where the crankcase is not clamping the bearing enough to stop its outer casing rotating.

If you have these kinds of problems (an occasional "graunch" while in 6th gear at around 70-80Mph, and/or it's dropping out of 4th) then you will need to strip out your gearbox, and replace this set ring. On re-assembly Loctite the bearing outer case to the crankcase. This should prevent a repeat of the problem.

If you have had these problems, I would love to hear from you, so please Email Me