A10 SR/RGS Jumps out of 3rd gear

[BSA_54A10]

So can you take your old gears with worn dogs out of the box and turn them down and bung them back in with some 'undercut'? As in obviously they will now be smaller, but presumably work OK? Could I do this on a lathe? (as in is it latheable, rather than do I have the skills required - ahem)

Firstly the gears & dogs are cased so it is not a job for the ametur.
next the undercut needs to be strait sided so you could only do it in a lathe with the tool mounted in the chuck and job fed in.
Relatively strait foreward on a mill with indexing table but a bit tricky with the dog mounted on the cross slide.
I have no idea how the undercut was done to the gear and Bob was not inclined to show me.
As he was a worls acknowledged Honda 4 expert ( Honda Japan sent their brightest mechanics to do 6 months under Bob ) and was doing this as a favour to me I was not about to push my luck as I have several other boxes I wanted done, but he got shafted intoretirement so they never happened.

[duTch]

 The longest detent spring I have is 2.605" (2.549" with light caliper friction preload), so I've used it, may or may not make a difference.
  That's only about .070" longer than the ~4.480"/2.525" spring I've been using. For the record, all springs are 0.038 wire by~0.315" dia. which appears to be metric specs. (1mm x 8mm)

  To determine how much engagement I have in third gear, I put the mainshaft with its two sliding gears and selector fork in place in the sleeve gear and in situ, and measured the sliding gear float best I could (between sel. fork cheeks) @ ~ 0.034".
 I also calculated that when the mainshaft is pulled snug to the bearing in inner case, is a difference of ~0.045" from being hard up against the sleeve gear. This added together gives 0.079" less possible engagement (~2mm).
 I forgot to measure how much the third sliding gear (E) engages with gear (G), will check in the morning if not working.

Question;- to reduce all this slop and reduced meshing, I wonder if adding a shim between the sliding gears, and between (G) and bearing would have any ill effect, other than moving the clutch out some...?

 Hope that makes sense, I had planned on doing a drawing, but.....maybe later

[bikerboy]

I had both 3rd gear whine and jumping out of gear.

I replaced two bushes (constant gear mesh it says in manual) 67-3073 and 67-3080. Once the gearbox was out it only took just over an hour and cured both problems. One needed drilling which was a p.i.t.a and they both needed reaming but it was not a difficult job.

Better than paying SRM prices anyway :)

[duTch]

 I determined that my box is an earlier version (pre '50?), the dogs being different so I swapped out some gears -probably most of the cluster in fact, and it's working fine but still whining. I renewed the bushes three years ago.

[Viking]

Update:
The gearbox was send to SRM for an complete overhaul.

Returned in June 2016.

Worked with by Moto Guzzi 1000 ccm for long distance cruising, so the BSA was not in use before late 2016.

Summer came late to Denmark this year and I am back on the BSA again.

More precise, more tight and no jumping out of gears…..

The following work was carried out:

M/shaft ground u/size sleeve gear bush fitted & honed,. Lay shaft ground 3. undersize bushes fitted and honed
New bearings, oil seals and bushes. Kickstarter ratchet changed, new push rod, etc.


“Stirling job”  , Wow the gearbox is working like clockwork now.
I recommend SRM for engineering jobs.
(The engine has the SRM bearing conversion done in 1995. Still works like at treat…..)

[duTch]

 I love my Gutzzi and I love My Bettza- but which do I loveda most ???