Gearbox shaft wear - mainshaft and layshaft

Not open for further replies.
Feb 18, 2007
Evening all.
I'm creating a new post for this question.

I have a question about what the tolerances (and acceptable worn diameters) are on the mainshaft and layshaft where the various gears rotate.

For the layshaft I don't have a lot of concern but would like to know what the 'as new' diameter is for the area that the 1st gear rotates and where the layshaft rotates in the kickstart bush. What is the 'as new' diameter?

Gearbox shaft wear - mainshaft and layshaft

The mainshaft is a bit different. The area where the second gear rotates on the mainshaft looks fine (and is nearly new except for polishing by the rotating bushing).

Where the sleeve gear bushings rotate on the mainshaft is what I am wondering about.

Gearbox shaft wear - mainshaft and layshaft

You will notice that two areas that are free from wear (as no bushing/gear runs on these areas) are the original diameter at 0.8100".

Where the drive side sleeve gear bushing rides, the shaft has been worn to 0.8091" which is not bad - only about 0.001".

However, where the timing side sleeve gear bush rides, the bushing has worn the drive shaft down to 0.8072" or near 0.003" undersize.

Time to get a new drive shaft?
Has anyone tried hard chroming a gearbox shaft and then grinding to size?
What clearance between the shaft journals and bushings is acceptable?
:? ?
Gearbox mainshaft wear

Hi Teeb, unless more experienced forum members say otherwise, I would say that 0.003" is an unacceptable level of wear on your mainshaft. I would bet your sleeve gear bushes are worn as well. Unfortunately, I think it's time to replace shaft and bushes.
Not open for further replies.