Gear selection issues.

Spider Wales

Spider Wales

Hero member
Location
Newport South Wales
I have started to get an annoying amount of false neutrals when changing down the gearbox. It's a bit disconcerting when you are approaching a roundabout etc and attempting to scrub off some speed to try and keep things a bit smoother rather that just using the brakes.

The up/down adjustment on the selector mechanism is centered, so I don't think it's that, but as it is a high mileage bottom end, I estimate 130'000 or so, it actually sounds like a bag of spanners to me, even after replacing all the bearings/chain/cush drive rubbers etc in the primary side, (Series 1 Motor) and the top end was worked on by Keith Nairn for a previous owner, Re-bore, 10-1's,Valve Guides/Seats etc, (I think the P/O reassembled it all though) so I am thinking maybe a weak spring on the selector drum detent. That is a lovely design isn't it, needing a total motor out and strip to replace it, but what do you, "more experienced" Gentlemen think? It still has the original specification 630 chain and sprockets from a Royal Navy chandlers stores fitted, (I have a 530 set up waiting in the wings to go on) but I also wonder if that ginormous anchor chain might be exacerbating my issues.

All thoughts welcome. :)
 
Is it the mainshaft that snaps with those 630 chains? I had that happen (but didn't realise) and had false neutrals etc. I have also had the little selector spring break, again false neutrals etc. Maybe you could have a little look with one of those tiny cameras? I bought one from Lidl the other week for £39.
 
The 630 chain certainly did make the gearchanges and, indeed, the whole bike less pleasant.
Try moving the up/down adjustment on the selector mechanism slightly south of centred and see if that improves things.
Also, as advised above, consider fitting a new gear lever return spring. When they get tired, the crispness of the gearchange suffers, before they finally fracture.

Gear lever return spring.jpg
 
If you have rearsets or a left side gear shift, you can get slop or drag in those out of the engine bushes or bearings. Try a spray with a can of lube, NOT WD40. A proper lubricating spray oil.
 
The mainshaft will snap with any chain if too tightly tensioned. Not even a #520 will actually stretch, it's not a rubber band!

The gearbox doesn't really shift too crispy to begin with, but the #630 chain can make it a bit worse. But it's usually the return spring, sticking shift shaft and/or the shift mechanism adjustment at fault if numerous neutrals pop up. Be sure to orientate the return spring so that a minimum of lever movement is present before spring pressure is encountered, a little bending of the legs is sometimes necessary. Also check if the eccentric adjuster hasn't come loose.

Good idea to simply replace the return spring every couple of decades.


piet
 
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