T'other day I was out with the West Kent VMCC lads, and me mighty WDM20 let me down, it was like the back brake was on..? It wasn't, so we ALL decided that the gearbox had seized, so into the breakdown truck it went...

Today I got out into the fettling shed, to have me a look see, the ONLY thing I found was the drive chain, it was Bow string tight..! Took the gearbox out and inspected it, all was well, so has anyone else had a drive chain go so tight, that it locked the back wheel up..?

What's the cure..? I've adjusted the chain properly, and the big nuts are Godziller tight, but is it tight enough, cos I THOUGHT it was that tight last time. Got to get it right, going to Belgium twice, and Holland once this year on it, not to mention riding it all over the place here...

Shaun, do you have these washers on the gearbox mounting bolts?
http://www.wdbsa.nl/download/65-4189%20Serrated%20gear%20washer.pdf

email (option): spacemonkeym@gmail.com

Matty, can't say I've seen them..? SO I guess NO..! So where does one get them..?

Although, thinking about it, I guess you're suggesting that the gearbox MOVED due to not having these..? Well, it didn't..! The Primary chain was as it should be, neither tight, nor slack, just perfect in fact...

Shaun, The rear wheel has moved I think, are the adjusters in place, and correctly tightened and wheel alignment correct ? Just my Two P worth, Andrew.h.

email (option): warbikes@gmail.com

Andrew, well I THOUGHT the adjusting nuts were tight and everything was in place, seems I was wrong, otherwise it wouldn't have happened. Must be that massive power the engine gives out, blimey..! Best I take a bit more care next time..

Hi Shaun

If the gearbox is secure then the probable cause is that the rear wheel is not adequately fixed in the frame and, while the driving force of the chain above the wheel axle would pull the wheel forwards and so slacken the drive chain, conversely, the effect of friction on the tyre contacting the ground would tend to move the wheel backwards in relation to the frame and so tighten the drive chain.
As the amount of friction is dependent upon the weight bearing down on the wheel you would appear to have 3 options. Tighten the spindle nuts, supercharge the engine or shed a few stone yourself.

Cheers
Pete

email (option): petercomley@web.de

Pete lad, shed a few stone..? BLIMEY..! I'm wasting away as it is, think it'll be a better bet to simply tighten up the spindle nuts. Everything is now working as it should, so that's OK then..

For once, a breakdown that cost me NOTHING, don't ya just LOVE the BSA 'M' series, course I'll be keeping me eye on things now, strange thing, that's NEVER happened to me before. Had the drive chain jump ship, on me 56 M20 once, but that was years ago, when I couldn't be arsed..