gear box issues ??

[triple]

Here,s something for you .
CB500 in racing kit. 3 rd gear occasionally seems to slip ( guaranteed its not the clutch as it would be more prevalent in other gears also )  ??
I have been told the gear itself is the issue and needs replacing but I need more convincing than that.

Only happens in 3rd. No issues with the balance of gears... quite odd , never experienced this type of thing before

very concerning when getting on the gas early in the corners. Feels like it jumps out then back in , sort off ....

any one have any ideas or experience with this issue ?

[SteveD CB500K0]

Mine did that.

It was a worn selector fork. Unfortunately they are almost unobtainium now...

Steve

[mickwinf]

the one that wears is the same as cb250/350k twins and can often be seen on ebay usa as thousands of them sold over there.

[SteveD CB500K0]

I only discovered that recently Mick (Ash's post?)

I bought a complete gearbox from a breaker just to get the required selector fork.

[matthewmosse]

On mine it was 1st and 2nd that developed that habbit.

[Bryanj]

When it starts its usually the selector(frequently the centre one) but once it has started the dogs on the gear get rounded along with the mating parts. When 500's were found racing commonly it was normal to "Undercut" the gear dogs to give a more positive location.

In your case i would think you need to replace a selector and at least two gears. The other known problem with 500's is primary chain wear which when excessive can eat into the main oil galleries, might well be worth changing at the same time

[AshimotoK0]

the one that wears is the same as cb250/350k twins and can often be seen on ebay usa as thousands of them sold over there.

Yes .. I got a pristine low mileage complete CB350K gearbox for £20 last year in the UK. The problem with the 250/350 is that the collar on the countershaft that carries the oil seal to the sprocket can corrode or pick up grit and wear. I got the £20 gearbox because of that. But I did consider maching down the collar and fitting a 1mm reduced ID oil seal, as I had that collar tested and it is not hardened but opted for the replacement gearbox.

Also the countershaft 500 bearing is part of the 400/4 gearbox complete bearing kit from Yamiya  I THINK... still need to check if they sell them individually, will do it today.

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