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I saw similar problems with some of the Honda dirt bikes in the 80s and from what we could gather the parts manufacturing was getting out of spec and wasn't picked up till some had been assembled and they would not pull them all apart but let it get fixed under warranty and it would appear that your fault has gone a long way past warranty. In the case of Honda it was the drum that was faulty.

Either the Shift drum bearing boss was not machined deep enough or the bearing was not fully seated at the factory. (Just a guess) Because the case is molded, I wonder if they left a piece of casting flash under the bearing, or the bearing just wasn't driven enough.

My theory could be wrong in that your issue seemed to be confined to 1st only.

I commend you for going to the lengths you did to find a repair for this problem, many people would have given up, or split the cases. Great fix.

Todd.

Thanks Todd,

It would appear that the bearing boss was not machined deep enough or the shift drum selector groove is misaligned. We did check that the bearing was seating firmly etc. and all looked good. It was only confined to first gear and it's relative selector fork, all the other up-shift gears, moving in the opposite direction to first, were meshing very well, hence my question, would anyone have an idea of a suitable/correct meshing depth of the dogs. If I had an idea of that, I think we would then be able to easily identify where the actual problem originated - Shift drum bearing boss depth or shift drum selector groove misalignment. This answer would now become a curiosity killer as thankfully my bike is running well and all gears are engaging satisfactorily.

Regards

Craig

Did you check if the gears that move in the opposite direction were over engaging.
At an educated guess I would expect to see 2/3 of the available movement used. i.e. how far the dogs engage without the restriction of the selector fork and how far with the fork working them.

Hi Rick,

It appeared that all the up-shift dogs, 2 - 5 were engaging fully, in other words right up to the face of where the dogs protrude from the relative gears - if that makes sense. So I would say that they were engaging 100% and not 2/3.

2/3 is what I would expect as a minimum. When I was drag racing many years ago in another life we always made sure of absolutely maximum engagement and sometimes found there were gears that would engage deeper than others but not to the extent you have described. It's a long time since I have worked on any of the Kawasaki gearboxes and not at all on a Z1300. Does the 1st gear on them work alone or does it back onto 2nd gear as a very out of spec gear could well do what you describe.