Plunger B31 Gearbox Fixings.

[yellow B31]

Attempted to adjust the primary chain on my 49 B31 with its two gearbox bolts assembles as per the parts list, i.e. bolts in from the off side nuts behind the primary chain cover. The rear nut is just accessible but the front one nigh on impossible unless there is a special spanner. My BSA instruction manual shows the front fixing opposite way round i.e. bolt in from near side nut on off side. Did BSA realise the error of there ways and correct it?
I plan to remove the clutch and rear cover, When a puller arrives, and swop it around. Was the parts list illustration an error or is there a special spanner?

[Greenfield]

Is the B31 the same as the B33 adjustment? I don't remember having a problem in accessing the three nuts apart from the fact that I had to lie on my side on the garage floor. I've taken photos of the three nuts on my 1950 B33 plunger to compare. They're not very sharp but hopefully you may be able to make things out.

[idie]

The bolts have a square on them to fit in slots in the mounting plates. You only need to undo the nuts and use the adjuster to move the gearbox.

[yellow B31]

Hi Greenfield. From what I can make from you photos it looks like you have a nut on the exhaust side. I don't have that. Mine are all on the clutch side.Will have a better look tomorrow. 

[idie]

It looks as if the the bolts are put in from the wrong side.Although not easy you can tighten the nuts when they are oñ the clutch side.

[martinh10]

From all the data I have seen I think BSA intended the nuts to be on the LH (clutch) side - don't know why but anyway that's where mine are. I have a thin (3/32" thick) 5/16w open-ended spanner and with the bike off the centre stand the nuts are quite accessible. The cheap spanners pressed out of sheet would probably do the job or you could grind one down on a bench grinder.

[yellow B31]

Thanks for reply's. BSA show both options in their documentation. My instruction manual shows the front fixing with its nut on the off side and far easier to ger at with a socket. When I remove the clutch and rear cover will swop it around.

My first experience with a B31 and a nice bike to work on.