Twin gearbox

[roy the mechanic]

Hi, the other day the gearbox in my trusty vin went "bosky", accelerating past a line of stationery cars, a nasty noise was noticed. I cannot select neutral, and there is an expesnive clankety-clank coming when pushing with the clutch disengaged. Any ideas what broke before I contact the bank manager for financial assistance? The "recovery service" from bikesure took four and a half hours to get there. By which time I had arranged my own recovery, and was five hundred yards from my house when the recovery guy phoned to say "I'll be about twenty minutes till I get there!"

 

[timetraveller]

Hi, the other day the gearbox in my trusty vin went "bosky", accelerating past a line of stationery cars, a nasty noise was noticed. I cannot select neutral, and there is an expesnive clankety-clank coming when pushing with the clutch disengaged. Any ideas what broke before I contact the bank manager for financial assistance? The "recovery service" from bikesure took four and a half hours to get there. By which time I had arranged my own recovery, and was five hundred yards from my house when the recovery guy phoned to say "I'll be about twenty minutes till I get there!"

 

[timetraveller]

My first guess would be one or more missing teeth on one of the gears but you will have to look inside to check it. When it happened to a racing bike I was working on there were several teeth missing off two meshing gears. Good luck with it. It might not be as bad as that.

 

[roy the mechanic]

Thanks T T, on the positive side, the cases are o-k, and it still has oil in there. Something has broken, luckily it did not lock-up! I seem to remember reading that there is a bushing that seizes somewhere due to a sharp edge? I'll get in there next week and, as they say , report according.

 

[stumpy lord]

Thanks T T, on the positive side, the cases are o-k, and it still has oil in there. Something has broken, luckily it did not lock-up! I seem to remember reading that there is a bushing that seizes somewhere due to a sharp edge? I'll get in there next week and, as they say , report according.

Roy, one of the weaknesses of the Vincent Gear box is that the selector pins in the selector forks (G29as) and (G2as) are not un known to fall out and drop into the gears with horrible results. I believe this happened to a member many years ago whilst crossing the Nebular plain in Australia with disastrous results.
As Norman said, you will have to go into the box to find out just what damage has been done. If you are lucky it may only be down to a pin being loose and dropping clear into the bottom of the box. If that's the case the pins can be replaced with pins that have a shoulder machined on them.
all the best ,
the other Norman

 

[Howard]

Fingers crossed it could "just" be a collapsed bearing.

H

 

[roy the mechanic]

The fallen out pin could explain the loss of neutral. The rhytmic clankety-clank whilst pushing sounds like broken-up gears. Panic not, after the trials with the "new" one , I am confident of a positive, if expensive, outcome. Thanks for the input, Roy.

 

[roy the mechanic]

Update time, Stumpy gets the cigar! Pin fallen out- broken g 11 + g8/1. All suppliers waiting for g11 to be made. So, if any-one has a spare I have cash to buy one. Roy.

 

[highbury731]

... one of the weaknesses of the Vincent Gear box is that the selector pins in the selector forks (G29as) and (G2as) are not un known to fall out and drop into the gears with horrible results.
... the pins can be replaced with pins that have a shoulder machined on them.

Is this a recommended preventative measure?

 

[roy the mechanic]

The spares co has them in stock. £ 3.97 each. So if you have nothing to do this winter, they may save a bill of the thick end of£350.00 for the parts to mend it.