BA gearbox sprocket removal mod?

[stu.sharratt]

Evening all ( for those of us in the correct hemisphere )

I've got my BA 'box apart at the moment & was looking at the shoulder on the mainshaft that prevents removal of the sprocket whilst the box is assembled.
It seems that the only purpose it serves is to prevent the clutch bearing riding along the shaft.
If I turn approx 2mm off the diameter,this would allow the nut & sprocket to be removed from the clutch end while still retaining the bearing.
Any thoughts on this mod ?...has it already been done ?...Is it a common mod I should know about anyway ?

cheers

Stu

[nevhunter]

It also limits the entire clutch rotating assembly from going where it shouldn't (as well as the cage for the small rollers I think) Can't the mainshaft be with drawn after the outer cover is removed and the nut on the end of shaft also. You might be unlucky there and have to fiddle the gears to reinsert the shaft, but I think it can be done. Nev

[ian.scott]

Yes, thats the way to do , Doesnt take long especially if you thread a piece of tube/rod through as you withdraw the mainshaft to keep the gears in place and you dont lose all the oil/grease

Ian

[graham.wade]

Interesting. I am going to have to replace the gearbox sprocket soon on my NH with a CP box, I assume the same trick will work?

Graham

[simon.holyfield]

I remove the mainshaft - obviously you have to disturb the seal on the end cover, but it's not too painful a job.

[stu.sharratt]

The fixed shoulder on the mainshaft doesn't itself act as thrust face against the clutch as its o/d is too small ( the clutch can pass freely over it ). There is a seperate loose thrust washer with a larger o/d that butts against it. (3394-36).
Having looked at it again, I'm sure its feasible to reduce the shoulder enough to let the sprocket pass over it, thats why I wondered if anyone had done it before.
Once the loose thrust washer is in place the clutch & brg sleeve are retained.
Guess I won't be changing the sprocket often though!

[nevhunter]

You are most likely right about the washer It's not very thick from memory. It's a wonder Burman didn't do it that way in the first place. To hold the new sprocket when tightening the nut I use a piece of old chain and a file. The file tang goes into a link and the other end of the file sits on a tooth of the sprocket and the chain wraps around the sprocket. Nev

[john.whiting]

The standard Burman BA mainshaft will pass the drive sprocket over the clutch spline.Out of only four postwar bike makers to use this box, one wont allow easy sprocket replacement,Ariel.So you could swap your bike for a Panther or a Vincent.And live happily everafter.Regards John.

[Eero.Korhonen]

Hello,
One trick I've heard:
1. Open the gearbox casing.
2. Open the main shaft nut.
3. The primary drive is open, you can pull the main shaft out with the clutch packet and
at the same time pushing the 1/2 " shaft in from one end.
4. Now you can change the sprocket without tear down clutch.
In fact, I have not tried this, and I do not know which model it is.
Br, Eero

[stu.sharratt]

Bugger, double checked & to reduce the mainshaft shoulder enough for the sprocket to pass over would leave barely anything for the thrust washer to seat against, its just too marginal.
You could safely take enough off to allow the nut to clear, but obviously the sprocket spline minor diameter is smaller again, so its a no go, bloody Ariels !
John, I was actually looking for a nice Panther last year, but I've had the VH lying around in boxes for so long I went this route instead.

cheers
Stu