[wessex_man]

I've pulled up Heathcote. The BMS sunbeam publication also copies much of this work.

" Gear-box (cam operated type). adjustment of control. A mark is cut in the sliding rack which operates the gears. This mark must be visible outside the gear-box when the change-speed lever is in neutral (free engine position). There are two nuts on the operating rod, one each side of the the eye-piece on the rack. By setting these nuts higher or lower on the rod, the rack can be drawn into the correct position. Leave these nuts quite tight after adjusting. Always check this setting any time that the gear-box has been moved."

In setting everything to the mid point neutral position rather than top or bottom helps averaging gear meshing errors,

The 4 speed box is more complicated than the 3 but it is better in use.

I hope this helps Kind regards WM.

[singleminded]

I checked on the gear detent positions last night. If I get 1st and neutral line up with the gate then 3rd and 4th are way out and the reverse is true if I line up 3rd and 4th.
I had assumed that the 4 speed gate that came with the bike was correct,maybe not.
The other thought is the position of the gearbox lever on its spline, it may be that if the lever is lowered on the spline then the travel of the rod to the hand lever may change..All to with arcs..John

[singleminded]

The hand change adjustment is possibly out .I have found that the adjustment changes depending on how tight the tank holding down bolts are,and also if the front or rear bolts are varied.My thought was if the adjustment of the lever is wrong it should be out more at either 1st or 4th rather than the intermediate gears because of the detented cam.
Of course I may be completely wrong,I often am these days..John

[wessex_man]

Considering the four speed box was used for a short period of time it's surprising just how many variations on a theme Sunbeam managed. With slightly differing internals due in part to different end plates. Of the five or so I've had there were at least three different types. So Id suggest you try and source a complete box if you can. Having said that are you sure that the problem is with the box and not the hand change adjustment?

[singleminded]

I may be on the lookout for some good internals for my 4 speed box or a complete box.
Going uphill recently the bike jumped out of 3rd gear a few times.I havn't had a chance yet to open the box for a good look.In theory the lever adjustment shouldn't be a problem as the '32 4 speed box has a cam and detent system inside.
If anyone has had this problem and cured it please reply..John