AJS & Matchless Owners Club

I have just finished building the gearbox on my model 20 but i have a problem , I can select first gear ok . neutral ok. 2nd ok 3rd ok and then i seam to have another neutral before getting 4th ?
Any ideas as to what i have done wrong ?

AJS model 20 burnam gearbox

If you're trying to spin it by hand on the bench, chances are there is nothing wrong with it at all. They can be fiddly to engage all gears on the bench if not spinning at a constant rate.

I have the grearbox fitted in the bike at the moment but i will leave it in and get the swing arm fitted first then fit the clutch plates then try ang get the primary chain case all put back together ( its been over eight years rebuilding it ) Every year i say its just about finished then along pops up another problem . i have rebuilt the engine and did just about everything to her !
Cheers !

I think when you get the rear wheel in and chain on to spin everything at once you'll find it should be ok. The B52 box is a very simple robust box but not quite as smooth as the AMC in it's gearchange action.

I will keep you posted as to how i get on !!!

Some Burman GB boxes seem to need shims between 4th gear and bearing to move the gear inwards on the shaft to ensure the dogs engage properly. If the shims are not there 4th gear disappears, as the teeth on the dogs are ground off (as mine did). There is probably information on the forum about this problem.

I seem to remember something about a batch of Burman boxes having a bearing housing in a casing machined too deep and needing a shim, but cannot remember when or where. Andy