G: Gearbox (Twin) Unyielding gear selector

[phsDommie]

Rode my C Rapide yesterday for the first time in several months. The engine started on the first kick and ran smoothly. I was able to shift gears from first to fourth quite easily but could not shift back down again. The lever "refused" to travel upward and, if not for the Manual shift lever, I would've been stranded. Interestingly, when the bike is at a standstill with the engine off, I am able to shift through all gears up and down with the foot lever without difficulty. The refusal to downshift with the engine running didn't change once warmed up. Occasionally, I was able to shift from 4th to 3rd, but only intermittently and couldn't get from 3rd to 2nd or from 2nd to 1st.
Before I remove the outer cover, I thought I'd seek your wise counsel and find out if this has happened to anyone else.
Thank you in advance,
Paul.

 

[Bazlerker]

Does the clutch free completely?

 

[Alyson]

I second Bazlerkers' thoughts.... might be a clutch issue

 

[phsDommie]

Thanks for your responses - yes, the clutch completely disengages and doesn't drag. I can roll the bike backwards easily with the clutch lever fully in.

 

[Gary Gittleson]

I can roll the bike backwards easily with the clutch lever fully in.

I'm not sure that's a sufficient test. Recently, I experienced a new phenomenon (to me). The bike shifted reasonable well up and down but sometimes became difficult to find neutral (with the bike running of course). Then on a trip of about 250 miles, it began refusing to downshift and even refused to free up at all. I found that if I pulled the clutch lever in and revved the engine, it would free up, allowing a downshift. Shifting from a standstill and upshifting was still OK.

A few days later, I tore down the clutch. I had recently resolved several problems with it but not the additional one I found. The centralizing pins were quite sloppy in their bores and the shoes were also fairly loose on their pivot pins.

So I bought new shoes from Coventry Spares. The VOC spares company was out of stock and besides, Coventry's stock comes from them. I know it's possible to refurbish the shoes but not without considerable work and proper tools.

The result was miraculous. The bikes shifts beautifully, up and down, into neutral at a stop etc.

My main point is that a small amount of drag might not be noticeable when rolling the bike but will still have a serious effect when shifting with the engine running.

Gary

 

[phsDommie]

Thanks, Gary, you may well be correct. I will add, however, that the clutch shoes were changed (new ones from VOC) only a couple of hundred miles ago. I will evaluate the entire clutch mechanism carefully.
Paul.

 

[Gary Gittleson]

Thanks, Gary, you may well be correct. I will add, however, that the clutch shoes were changed (new ones from VOC) only a couple of hundred miles ago. I will evaluate the entire clutch mechanism carefully.
Paul.

That's good. But my main point is that a small amount of drag, hardly noticeable at a standstill, get magnified when the engine is running. You're right. You need to check all aspects of the clutch. They are numerous.

 

[Bill Cannon]

Maybe a problem with gearshift pawl return springs?

 

[Peter Holmes]

I don't know if this is relevant, but whilst at the International Rally in Italy the clutch on my bike became particularly recalcitrant, or to put it another way, almost bloody impossible to operate, I started to fear for the gearbox internals, so bad was it, although starting and engaging first gear was not too bad. On investigation it turned out I had been a little careless and overgenerous with silicon sealant on the mating face of the C20 nut, a small amount of the silicon had oozed out and contaminated the bearing surfaces between the C20 nut and the C17 bush. Once that was all cleaned up the clutch and gear changes reverted back to silky smooth operation, and I am pleased to say the gearbox seems to have survived also, having ridden a good few thousand miles since then (2015)

 

[robin]

Have you tried adjusting the battery carrier nuts? Screw them outwards.