Gs1000 gear box problems

[wraith]

Any ideas,

The gear box in my gs1000 (chain drive) is playing silly buggers.

Some times it will go in gear and all the way through to top, other times it will jam in top or a false neutral between 4 and 5. 1st and 2nd are gritty as well (all with eng not running). Had the clutch cover and clutch out: still the same. Will come out of gear/ down the box if I take off the foot gear bit and put mole grips on the shaft, but this does not work all the time and you need to f**k about.

So any ideas of why???

Also had a look at a set of spare crank cases and box that's in them (no clutch in it) - and the gears, using mole grips on the shaft, won't go above 2nd even when rotating gearbox by clutch shaft. Does seem easier into and between 1st and 2nd though. Is that buggered too, or... ?

Neither box or cases ever come off an engine run by me, so don' t know what the score is.

[Markz9]

Usually if the gears don't engage properly or won't disengage it's worn sides on the gear selector dogs look at your spare cases and see if they are scored I wouldn't use moles too much you will bugger the splines on the gear shaft and that will need replacing as well 

good luck 

[Captain Chaos]

obvious things first. Chain adjusted correctly?

[wraith]

7 hours ago, Captain Chaos said:

obvious things first. Chain adjusted correctly?

What chain? Engine just put in frame  other bottom half on work bench.

Edited October 7, 2016 by wraith
Added a bit

[wraith]

17 hours ago, Markz9 said:

Usually if the gears don't engage properly or won't disengage it's worn sides on the gear selector dogs look at your spare cases and see if they are scored I wouldn't use moles too much you will bugger the splines on the gear shaft and that will need replacing as well 

good luck 

Cheers will have a look 

[wraith]

Just been into the garage, and split and had a look at the bottom end which is on the bench. Gears move free, cogs etc look OK, dog bone/selector forks don't look badly scored (4.75 to 4.77mm where they slot into the gears), pins seem OK - though will check all to manual's tolerances in due course - if I can find them...

BUT-  the selector/ shift drum will only go round to 1st, neutral and 2nd (very occasionally & with force 3rd) then jams. Will move with change shift rod ( moles on shaft not splines ) or moving drum with fingers or screwdriver, all real easy for 1 & 2, then locked solid. ???

Going to strip that out and have a look.