Gearbox Noise

[simon.holyfield]

If you talk to AOMCC gearbox spares I suspect you will find he can tell you what you need to know if you can't find it in Waller.

Thanks Paul. Turns out I must have trawled the gearbox section in Waller - I wrote down all the tolerances and end floats in a blog post when I built that gearbox 10 years ago...

I'm losing my marbles!

[JohnnyBeckett]

hi, just get on to Geoff Brown at the clubs gearbox spares if he does not know, no one will know

[simon.holyfield]

hi, just get on to Geoff Brown at the clubs gearbox spares if he does not know, no one will know

Thanks for the tip Johnny; co-incidentally I had half an hour on the phone with Geoff this morning.

The service we get from our club is simply astounding, and better than most modern bike dealers - not to mention spares prices!

[simon.holyfield]

Latest on the noisy BA in my Mk1. End float on the mainshaft, 40 thou; layshaft, 12 thou; selector shaft, 10 thou...

All way beyond spec, but I have a suspicion the gearbox sprocket is loose, so I will look at that (I have a new clutch centre to fit anyway), fix it if necessary and measure all the end floats again before I go any further.

[paul.jameson]

I wonder what you have as a gasket between the kickstart cover and the main gearbox shell. There were some pretty thick gaskets for that joint about a few years ago but it should be a thin paper one.

[JohnnyBeckett]

hi when i rebuilt my gearbox with all new parts from Geoff at the club spares , the clubs thin gasket made the kickstart and gear change stiff and i had to get a thicker one from Drags

[simon.holyfield]

The latest news is that the BA gearbox from my Square Four is now stripped and washed out. If you recall, some dogs were clattering at idle, in neutral.

For the record, there's 0.88 mm (35 thou or just over 1/32") end float on the main shaft and about 0.23 mm (9 thou) on the layshaft and selector. I've improved these numbers from my previous post by fixing the DTI more securely. There's no gasket fitted between the inner cover and the shell.

The worst damage I have seen is on the layshaft clutch first gear dogs and the layshaft first gear. This is always noisy going in; my clutch basket isn't brilliant and I have a new one to go in. The clutch drags when hot and I think that's what causes this damage.

The selector forks are straight and have a nice sliding fit, minimal play, in the mainshaft sliding gear and the layshaft clutch:

Here's a video looking at all the gears:

VID_20240123_174017.mp4

(263.61 MiB) Downloaded 29 times

As to the rattling/clattering at idle, I'm not sure. There's a lot of end float in the layshaft and selector shaft (Waller says 1-2 thou minimum but doesn't define a maximum) which could give rise to this clattering -particularly if one shaft goes one way and one the other, but although the mainshaft float is at the end of it's limit I can't see how that would cause the noise.

Grateful as always for your advice!

[nevhunter]

That noise could be coming from the clutch plates.
Assemble everything in the intermediate cover and move the selectors to go through all the gears and see IF anything gets close to tipping some other Part it shouldn't . Nev

[Mick D]

Hi Simon

Did you check out the condition of the selector mechanism as suggested?

How worn is the main shaft small, (kick start end), bearing? I don't think that's the cause of the noise but could be contributing to the end float.

Regards Mick

[simon.holyfield]

Not yet Mick - basically I only had time to pull it out and get it clean. The forks look good and they are a good fit in their grooves; they move easily on the drum but I haven't had the pins out yet.