SOHC.co.uk Forums > CB750
5th gear problem???
Johnny4428:
Thanks guys for diagrams and info, it’s unfortunate that I seem to know a lot more about it now than I did when it was in pieces. But the reality is I tried just to put back together as I found it to the best of my ability, albeit with some new bearings and bushes. Maybe have a go this weekend to take engine out and open up, at least I’m armed with a bit more knowledge goin in this time.
Johnny4428:
Just an update on findings. There seems to be excessive end float on 5th gear which must have added or even been the cause of this problem. (At least 2mm) This because of the low insertion from 2/3 plus a little wear was allowing the gear 2/3 to be thrown out of 5 and jamming between selector fork and gear 5 causing a bit of heat as can be seen from photos. So that has left me now probably having to replace gears 2/3 and 5. Also have to look for shims to pack out 5 from case.
McCabe-Thiele (Ted):
I know yours is a different model but on my 400 I had an issue with what felt like excessive end float on the gear shafts. I was worried about adding extra shims in case it led to a locked up gearbox when the engine was hot.
I ended up changing the outer half clip bearing retainers and fitting some new outer needle earrings plus the locating pins. When I bolted the Crank case halves together I made sure I put some Hondabond on the outer races to keep the keep the shaft float at a minimum. Remains to be seen if its worked long term.
Johnny4428:
I wouldn’t be frightened to take up most of the end float on this Ted, but I would need to find out how much end float is supposed to be there.
K2-K6:
At least you've got a diagnosis now and certainly worthwhile taking it apart again.
I can never resist changing gear on boxes after putting them together to see what they feel like before running them, just a fascination in how they work really. You can pick up reluctance at that stage so suppose it helps.
Went to look at a Kawasaki Z1000 (from memory) that a friend's friend had difficulty with as it would only select first gear. He'd had the motor out to paint the frame without working on the engine, put it back in and found this non selection, then pulled and stripped bottom end but found nothing. When we went through it and found a neutral finder device that was supposed to do this, three ball bearing in arrangement that flung out from centrifuge when the output sprocket shaft rotated. No road speed and only first or neutral available, nothing wrong at all. Hadn't seen one at that time as Honda didn't use them.
Hopefully you'll get this one back to scratch again without big costs.
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