500 gear shift drum

[Lyndoneil]

Not sure if that's the correct title, but the mechanism  that operates the gear shift forks, with the pins inside it that the gear  selector mechanism turns against.
As you  see I'm desperately trying to avoid  splitting the crankcase as I know what a disaster that could turn out to be.
The cams were out originally because I was measuring the valve clearances,  so now I have put the topend back on, unfortunatly not before as I was trying to get the link pin in, the camchain suddenly developed a mind of its own and vanished into the botton of the crankcase, then the magnetic extendable pen tool decided to snap in there too, was a bit naff anyway. So had to have the head off again to fish it all back out.
Anyway getting back to the point! If I spin the input shaft (clutch shaft) and change the gears either manually, or even easier with an Allen key into the bolt holding the shift drum in place, the gears are changing in a pretty good  fashion on all the gears up and down,!
Which I am sure tells me something, just not totally sure what!
Maybe new gear shift assembly and spring (Gear lever shaft etc)
Any ideas anyone?

 

[Paul Marx]

Well, you might not need to split the cases.

I had some worries when I rebuilt a 500 for my ex wife many years back with the nut on that two armed selector thingy.
Too tight and you get gear selection problems, not tight enough and the thing jumps out of neutral.

Wait for somebody well versed in 500s turn's up, which is not my case.

Paul

 

[Dellortoman]

Allen key into the bolt holding the shift drum in place, the gears are changing in a pretty good  fashion on all the gears up and down,!
Which I am sure tells me something, just not totally sure what!

it tells you that the shifting mechanism inside the crankcase is working OK. Seems your problem (if indeed there is a problem) is with the shifting mechanism between gear lever and the rotating drum. It probably just needs adjusting.

 

[Gareth99]

I agree with Dellortoman.

The linkage system that is missing from your photo could be the problem and my experience tells me they fall into two camps;

There is a tiny spring that keeps the toggle plate pushed down onto the selector drum (the one with the pins in it). This spring breaks very easily and although gravity will keep the toggle plate in place in most instances, when it bounces up you will get many a missed change and uncertain selection issues (especially on downshifts).

The second issue relates to the outer casing. The gear shift shaft sits in a boss in the engine casing and the other end is supported by a hole in the alloy outer casing. This hole wears and allows the selector shaft to move and this causes selection issues. You can alleviate it a little bit by moving the selection linkages around, but I've had to resort to a bronze bush to stop the wobble.