Shimming of loop frame 4 speed gearboxes. Advice needed.

[Rolf Halvorsen]

Hi all

I know about shimming of the 5 speed gearboxes selector drum, and the required lenghts of the main shaft with shims, and the lay shaft shims.

After working with more than 100 ea. 5-speed boxes, I now have started on my first 4-speed. Also done some 6-speeds (first and second version).

The drawing sheet of the 4-speeds states 1ea. shim in front of the selector drum. (0,6mm/0,8mm/1,0mm/1,2mm). On the opposite side it has no shim. I have tried with 2ea. shims of 1,0mm = total 2,0mm to be perfect. Should I put one on each side?

What about shimming of the main shaft? I cannot find any recommandation?

So advice is wanted.

Rolf

[bigbikerrick]

Rolf, you may want to post your question, over on the "Loop List", or loopframe forum.  Charlie Mullendore, and some of the  other fine fellows  over there may have more knowledge of the old 4 speeds.
Rick.

[John Ulrich]

I shimmed both ends......  even with new shift pawls, it would not engage 2 gears unless I centered the drum.

[John A]

I shimmed both ends......  even with new shift pawls, it would not engage 2 gears unless I centered the drum.

Was that the one we did here? did you have to go back in or did we get it right?

[John Ulrich]

Was that the one we did here? did you have to go back in or did we get it right?

Of course we got it right!   

[John A]

I thought maybe we did but it was so long ago 

[Rod]

I'm in the middle of shimming my 4 speed now.
If possible, check your forks for wear and see which way the drum needs to move. But that means keep track of where they were and which way they were facing. (I didn't! But fortunately I took a picture and was able to figure it out.)
Once you've established your total shim width (no play but drum easily rotates), you have to make sure it lines up on the forks.
There's a couple threads about how to do this on Greg Bender's site. But 4 speed info is limited.