850 gear box

Hi my 73 850 has developed play in the kickstart shaft grabing hold of ths kickstart you can push and pull the shaft in and out . what do I have going on in there.

Most likely the layshaft bearing is failing. Much has been written on this forum and others about it so i would say read up an open up the gearbox it is not that hard a job an if the bearing fails it can lock the gearbox an rear wheel so causing you a nasty accident which will be much harder to put right both for the bike an the rider.

Has it "developed" or just never noticed it before? Kickstart shaft is an extension of the layshaft so any in and out movement indicates end float on the layshaft. Some end float is normal. Layshaft is located by a ball race at sprocket side of gearbox and runs in a bush in the end of Kickstart shafts. I would worry if the Kickstart moves down when accelerating away from standstill, this indicates layshaft bearing failure. If this is happening do not use bike.

If the kick starter rotates then yes, stop riding, and replace the lay shaft bearing, else you and your bike will be sliding down the road together and no manner of pulling in the clutch will help you.
However if it is end float that's a different story.
End float is normal, I had end float in mine but it was a bit excessive.
It caused no dramas normally, except occasionally it would jump out of first gear and into neutral in the most undesirable places.
It would drop out when I back off the throttle.
You know when going around a tight mountain switch back corner, leaning over as far as you dare, then back off a little, and then its in neutral.
It is about this time that the laws of gravity, inertia and the pendulum effect take over and you find your self lying on the road, bike beside you, or on top depending on how unlucky you are.
But just to keep me on my toes it only did it ever now and then. I'm sure it waited until I was relaxed before it did the got you.
Any way I shimmed the shaft and it has now been a few years without the boogie man returning.

Cheers
Peter R

mike 850 said:

Hi my 73 850 has developed play in the kickstart shaft grabing hold of ths kickstart you can push and pull the shaft in and out . what do I have going on in there.

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The kick start shaft is independent from the layshaft. Pushing in on the KS it will bottom out on the layshaft, pulling out will make it seat against the intermediate case. This is all normal and you may not have noticed it before. As far as shimming the shaft, I myself have never had to do this on any of my nortons/AMC gearbox's and feel it is a bodge repair to compensate for worn gear dogs. 2nd, 3rd and 4th gear have reverse angle dogs that aid in engagement retention. Only first gear has parallel faced dogs and when worn and rounded they may try to push out of engagement. To me, shimming is an admission of a worn gearset or a bad first gear or layshaft bush.

shimming is an admission of a worn gearset or a bad first gear or layshaft bush.


My first thought was worn first gear dogs but upon inspection they were in good condition. Somewhere I found the end float specs and mine was excessive, so I decided to bring it back to spec, However I did replace the bush even though it didn't seem too bad just because I had it apart and to eliminate another possible cause.
Perhaps that's what actually did fixed the issue who knows.
All I know is the problem never re occurred.

Cheers
Peter R