Author Topic: Bsa b33 1946/48 gearbox  (Read 823 times)

0 Members and 1 Guest are viewing this topic.

Norton650

  • Star
  • *
  • Posts: 20
    • View Profile
Bsa b33 1946/48 gearbox
« on: 16 June, 2020, 10:19:45 »
Hi I have a b33 1947 with the 1946/48 gearbox I have rebuilt the box several times now but every time it seems to tight like it nearly impossible to turn by hand it came to me in bits so not sure if I'm missing some  shims or could it be something more serious if any one has got a diagram of the 1946/48 box would be great have looked on draganfly and searched the web but very little information on this gearbox  many thanks  clayton

JulianS

  • Empire Star
  • *****
  • Posts: 2417
  • A10
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #1 on: 16 June, 2020, 11:07:40 »
 BSA service sheet  302 may help.

Norton650

  • Star
  • *
  • Posts: 20
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #2 on: 16 June, 2020, 13:48:05 »
Thanks for the diagram seem like all is correct

morven21

  • Star
  • *
  • Posts: 36
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #3 on: 16 June, 2020, 17:26:26 »
Is it poss that one of the roller bearings is not quite seating  dead square, an right at end of it's recess? Just 1-1.5 mm out of square will load up the shaft, causing tightness. Bon chance.

GLENN

  • Royal Star
  • ***
  • Posts: 117
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #4 on: 16 June, 2020, 19:08:32 »
I've come across this probem previously and one of the fixed gears on the mainshaft wasn't pressed on far enough.  Could be that?  All the best, Glenn

Jim S

  • Blue Star
  • **
  • Posts: 68
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #5 on: 17 June, 2020, 02:38:52 »
Could be the shifter forks are not sliding freely in the dogged wheel slots. Caused by:
-bent forks
-incorrect shimming of the shifter shaft

Dennis49

  • Star
  • *
  • Posts: 31
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #6 on: 17 June, 2020, 18:08:52 »
I have just rebuilt one of these! Mine would not change into 2nd. I took it out of the frame and stripped it completly.Took out the shafts and found some damage to the selector fork.This was in stock at Dragonfly. There was a slight burr on one shaft,which I dressed with a diamond file. The 2nd gear selector dog was not really free to glide up and down the shaft. However turning it round by 180 degrees freed it. Its called selective assembly. I then fitted each shaft into the box individually and checked the end float. I adjusted them all to .005 .I found the spacer on the selector fork shaft had been missed out by the previous owner. It works fine now. Good luck,you need to strip and rebuild the box numerous times to get it right. Happy to help if any of this seems a little vague.

Dennis49

  • Star
  • *
  • Posts: 31
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #7 on: 17 June, 2020, 21:15:39 »
Hi, if you check my post regarding zb32 gearbox on here there is a very detailed guide to stripping this gearbox. I found it very useful.Dennis.

cdsdorset

  • Royal Star
  • ***
  • Posts: 185
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #8 on: 19 June, 2020, 19:29:29 »
Have you tried rebuilding it with 2 gaskets between the main casing and the intermediate one.

Norton650

  • Star
  • *
  • Posts: 20
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #9 on: 22 June, 2020, 05:11:26 »
After another day playing with the gearbox still not right as soon as I put any torque on the casing bolts the box starts to get tight again just thinking would the 2 gaskets trick work unless I  have a bent shaft maybe if I rotate the box backwards I have
 noticed that the gears move across towards the casing cover

Norton650

  • Star
  • *
  • Posts: 20
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #10 on: 23 June, 2020, 09:12:42 »
Does anyone know the thickness of the shims that go on the end of the 3 shaft before the end cover goes on as I was wondering if these could be to thick /thin maybe they were the only ones in the box with the gearbox bit on so may not be the right ones

Jim S

  • Blue Star
  • **
  • Posts: 68
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #11 on: 24 June, 2020, 02:27:29 »
Try building the gearbox without the shims.

Also, try building with just the main shaft the the main shaft plus selector shaft.

Pete C

  • Royal Star
  • ***
  • Posts: 236
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #12 on: 24 June, 2020, 05:35:13 »
As mentioned avove, you need to shim each shaft seperately, one at a time, in the cases to get the end play for each shaft before you assemble them all together. If you don't use a gasket while you do this, aim for zero end float, which will then give you around 10 thou when the gasket is installed.
I did one of these boxes a year or so ago and they are pretty much the same as the later gearbox...except for a few details and that bloody awkward kickstarter spring!!!

Norton650

  • Star
  • *
  • Posts: 20
    • View Profile
Re: Bsa b33 1946/48 gearbox
« Reply #13 on: 09 July, 2020, 15:02:18 »
Hi all finally got that 1946/48 gearbox sorted what a job but got there in the end working perfectly on the bench so can now get on with the rebuild thanks very much for all of your information and yes that bloody kickstart spring what a pain