Unable to get neutral when hot - cause found

[pxc433]

Bike is a 1988 R100RS with 100,000+ miles.

The problem I had (and posted on here about a few years ago) was that when hot it became impossible to get neutral. To cut a long story short, as I had overhauled the gearbox I thought I had made a gearbox reassembly error. This blinded me to other causes.

Late last year I noticed that when hot, and with the clutch pulled fully in, the bike wanted to move forward. Putting the bike on the stand I could see that the back when was definitely engaged, with 100% clutch application. Only happened when very hot - it had to be hotter than it usually gets in Scotland.

During the winter I replaced the clutch diaphragm, and the actuation rod. The actuation rod was original, and the diaphragm about 50,000 miles in use.

Comparing the old and new parts, they were almost the same, but the graduated part of the rod was subtly different.

Anyway, the gear change issue (and the clutch issue that caused it) are gone, regardless of temperature. I think some weird thing was happening with the diaphragm and the rod, but only when very hot. It's great to have the bike back to perfect.

One of the things about owning the bike since 1990 and doing 100,000 miles is stuff is just wearing out, and it's sometimes hard to see. Examples recently include the throttle assembly which had just worn down and changed over the years.

Love the forum, though I don't post much. Regards to you all.

[gspd]

...when hot it became impossible to get neutral...
...when hot, and with the clutch pulled fully in, the bike wanted to move forward.
...I think some weird thing was happening with the diaphragm and the rod, but only when very hot.

Obviously a heat related issue. I've dodged a lot of surgery when dealing with similar heat related clutch issues in the past when all the usual suspects had already been eliminated but the problem persisted. Here's what I eventually figured out. This has worked quite a few times, and it's free:
(remember, you heard it here first )
First you have to get the bike hot enough for the problem to manifest itself. Then, back off the 4 main transmission to engine mounting bolts about one turn. Then, with the engine running and while holding the clutch lever to the handlebar, retighten those 4 bolts evenly. This seems to cure many ailments by allowing the trans and engine to self align perfectly. oh, and did I mention, it's free!

[andrewmoto]

Bike is a 1988 R100RS with 100,000+ miles.

The problem I had (and posted on here about a few years ago) was that when hot it became impossible to get neutral. To cut a long story short, as I had overhauled the gearbox I thought I had made a gearbox reassembly error. This blinded me to other causes.

Late last year I noticed that when hot, and with the clutch pulled fully in, the bike wanted to move forward. Putting the bike on the stand I could see that the back when was definitely engaged, with 100% clutch application. Only happened when very hot - it had to be hotter than it usually gets in Scotland.

During the winter I replaced the clutch diaphragm, and the actuation rod. The actuation rod was original, and the diaphragm about 50,000 miles in use.

Comparing the old and new parts, they were almost the same, but the graduated part of the rod was subtly different.

Anyway, the gear change issue (and the clutch issue that caused it) are gone, regardless of temperature. I think some weird thing was happening with the diaphragm and the rod, but only when very hot. It's great to have the bike back to perfect.

One of the things about owning the bike since 1990 and doing 100,000 miles is stuff is just wearing out, and it's sometimes hard to see. Examples recently include the throttle assembly which had just worn down and changed over the years.

Love the forum, though I don't post much. Regards to you all.

Great detective work, @pxc433! It's always satisfying when you finally crack a stubborn problem like that. Ride safe and enjoy that smooth shifting!