I’m doing a resto on a MK1 LeMans and have had to strip the bike down to it’s last nut, bolt and ping-fuk to get everything clean.
I sent the engine gearbox and bevel box cases to Stephen Smethurst for him to make them better than new again.
I carefully placed all the gearbox internals in storage as they came out to prevent any nasty surprises, given it’s a box I’m not familiar with. I’ve wriggled everything back in, in the same order as it came out and wanted to nail the lid back on. Whilst it seems to change through the gears OK, it is set in neutral now, but there seems to still be drive. My guess is that I need to bolt the lid back on to get everything to line up perfectly to get a ‘real’ neutral, but if I do that I will squash the nice new gasket if my guess is wrong. Also I have noted that when the lid is put even a bit on then one of the rods through the selector drum comes out of the bottom messing the jigsaw up. I prefer to feel the gearbox go through its cycle before nailing the lid on whenever possible. The last box of this type I did was and old R100 box where the input shaft bearing had detonated - that was a strange one!
You should be able you put the lid back on to try it out. The gasket gives the 1mm clearance required when its running proper. The lid stops the shafts splaying apart and causing the selector forks to drop out.
Are you sure its not just drag in neutral.
I suppose the first question is did it run and select all gears properly before you took it apart.
Not sure about the drum shaft falling through, though. I didn’t think it could do that
Have a read of the re-assembly section in this guide
By the rods dropping out, I assume you are referring to the short rods that the selector pawl latches onto to rotate the selector drum. I don’t recall an issue when I did mine, but it was a long time ago! This picture may help.
Thanks for that. The PDF is very interesting. Given what it says about the lack of interest in shimming in the factory it’s probably worth measuring it all. I took the view that as it was (presumably) working before disaster struck and the previous owner accidentally set fire to his house, with the Guzzi being the only survivor. A very sad story. I’ll talk to the current owner and ask his feelings, but it seems sensible to go through it with a fine tooth comb.
The shaft that comes out with the lid is the selector shaft, and once it’s out of its home in the bottom it’s a sod to relocate!
There shouldn’t be any drag, given there’s no oil, oddly it seems to turn quite a way (maybe half a turn?) freely before seemingly engaging.
I have no idea about the bikes history as the current owner has never had it running after inheriting it following a dreadful tragedy - see my other reply. He started stripping the bike but ran out of experience and handed me a big pile of bits!
When I changed my clutch I decided to fit a new shift return spring as a precaution. I had the same problem i.e. the selector rail was pulled partially out when I took the cover off. A bent piece of wire was quite handy for getting it all back together I recall.
My bike is a loop-frame so this may not apply in a Tonti bike, but I failed to adjust the selector before I put it all back together. The little screw was not accessible so quite a few bits needed to come apart again!
Hi Ralph, re your Le-Man’s I don’t think there is a lot of difference between the loop frame or Tonti gearboxes apart from the angle that the speedo drive exits the case,
When it comes to assembling my boxes I always assemble the gears into the end cover with all of the shafts facing upwards,
you can then hold the output shafts in your vice with soft jaws, when everything’s aligned slowly lower the main gearbox case down onto the end cover, this way you don’t loose your shims and that’s another story.