Evenin' all. The poorly operating gearbox saga continues apace. Seems like the inability to engage first gear (nothing but the sound of drive dogs graunching) actually had nothing to do with out-of-adjustment linkages at all.
The box is now out of the bike and has been stripped and cleaned but the basic problem remains, namely neutral, 2nd 3rd and 4th can be selected OK, but 1st remains elusive.
I'm guessing there should be more/less endfloat in one of the shafts,so is there a "real world" guide to setting up one of these boxes anywhere on the Net? I have access to the BSA Service Sheets, but they were written when spares were available and simple replacement was the norm. I'm sure they didn't really anticipate someone in 2012 would still be messing around with these old bikes, or even anticipate the wear, abuse and general bodgery that would be inflicted on them.
Any hints, tips or links? Thanks in advance.
email (option): kevin.sandford@ntlworld.com
Hi Kev..Use the 'search' facility on the website to try and find previous postings on the subject..I have made a number of fairly detailed ones at different times.
Unfortunately, unlike the later swinging arm BSA gearboxes, the earlier BSA boxes have numerous features which can affect if, or how well, they function.
Later versions had the tooth form of the selector dogs and gear faces modified to aid engagement and these later parts can be retro fitted..like wise with the selector fork assembly. This was modified to improve the cam action and again this later part can be used to improve the operation of the box.
With the 'standard' WD parts or the later parts gear selection problems are often caused by 'lost movement', frequently caused by excessive end float of the mainshaft, layshaft and/or selector fork shaft which combine to compromise engagement of the selector dogs and gears.
Wear in the selector fork cam track and/or pins resulting from incorrect operation/asssembly and wear of the selector fork ends and selector dog grooves can also be a factor in affecting the degree of movement of the selector forks and dogs....
The bushes in 1st. and 2nd. gears on the layshaft and 3rd. gear on the mainshaft which are nearly always worn beyond the specified limits can also affect engagement.
The gearbox also has to be set up correctly on assembly as shown in the worksheets.
Regarding shimming of the shafts for correct end float it is easier to shim each shaft seperately in the gearbox case before building up the complete assembly...Ian
email (option): ian@wright52.plus.com
Hi Robb..I wouldn't claim to be the 'expert' who knows everything on these matters...and video presentations really aren't my style.
However, I shortly have to do a gearbox overhaul on my own M20 so I will do some photos and a full write up for inclusion on the 'technical section'.
I've been meaning to do this for some time as gearbox queries are a regular theme on the forum and though not complicated in principle there are lots of point to watch out for when assessing and rebuilding them....Ian
email (option): ian@wright52.plus.com