Can't get neutral when hot

[pxc433]

Hi guys

I've just returned from a 3000+ trip to Europe. Bike was great - flawless - except for one thing.

Bike is a 1988 R100RS. But the gearbox was overhauled by me 5 years and 30,000 miles ago. Bike has covered 96,0000 miles now.

The 'box was from a 1984 bike. I replaced all the bearings, and the input gear which was knackered. I upgraded the selector cut-out template thingie with a new later (upgraded) type. The 'box feels actually good on most changes, sounds OK, and is not depositing tell-tale flakes into the oil.

The issue is this. When the bike is very hot, I can't get neutral. In my native UK it never gets hot enough for this to be a problem, though a couple of times riding in London (high congestion, lots of heat) it does happen. When I go to France where is is much hotter, it happens a lot.

I'm not averse to re-opening the 'box, but to be honest it would achieve nothing at this stage as I've no idea what I would change.My shimming into place of the end-float of the shafts was careful, but that doesn't means I didn't make a mistake...

Any ideas or suggestions welcome. I want to get it to 100,000 miles next year on a nice trip abroad, when the bike will be 30 years old.

[barryh]

Have you confirmed that the clutch is releasing properly by rotating the rear wheel by hand while in gear. If it's not that then it could be lack of spline lube or something inside the gearbox. The latter is beyond me and you really need a gearbox overhauler of some experience to comment.

[Zombie Master]

Might just need a clutch adjustment. When things get hot it could change the operation.

[dougie]

Might just need a clutch adjustment. When things get hot it could change the operation.

+1.

[Roy Gavin]

For years folks were setting end float too close- the current factory figure is around four to five times what folks were setting them at, and getting the box hot compounds the problem
Richie Moore in England has the correct figure, and he has posted it on the UKGS'r forum on gearbox threads.
Wont quote it is it upsets most folk and they get upset and emotional when they see it - I am probably going to get enough stick from my post on the Mono final drive as it is---.
There is also a round plastic bobbin in the push rod mechanism which can swell and jam, and some have sanded the OD to restore the function- again a search on the UK site will reveal a recent thread.

[pxc433]

Thanks for the comments about clutch adjustment - I'll start there, as it's the easiest to test first.

How do I check this -

- Get the bike as hot as I can
- With the engine running, place the bike on the centre stand and check that the rear wheel does not turn at all (I recall it always drags a bit)?

or

- Bike cold, place on centre stand
- Rotate wheel. What am I checking for here? A low level of resistance? I'm pretty sure the engine won't turn.

[pxc433]

With regard to Roy Gavin's post, I think this is the link:

http://www.ukgser.com/forums/showthread ... tion/page2

In that he (Richie Moore) says .005 and a max of .015

To be honest I can't remember my setting. BUT his other comments resonated with me. When cold, I could turn the input or output shaft easily, and could even change gear. But starting at the clutch is the way to go for now.

[Zombie Master]

Just adjust it so the clutch lever engages earlier. Could be at the cable on the handlebars if there is enough adjustment available or at the lever behind the transmission.

[Zombie Master]

[George Ryals]

Since aluminum (the trans case) expands (the case gets longer) at a much faster rate as temperature rises than steel shafts, the end float increases as the temperature of the transmission goes up. So its not your shim job!