Drive train Shunt

[Barkstar]

I realise it’s a bit of a cheek seeking help before even contributing but here goes
I have XS650B and currently have a problem with drive train shunt. Even if you ease the clutch out really slowly there’s a clunk you can hear and feel. It’s clearly not good and something somewhere isn’t happy. Paying very careful attention to all the adjustments alleviated it a bit but failed to eradicated it. It hasn’t always done this.
Figuring it was likely failed springs in the clutch basket I stripped the driver side and found nothing wrong with the basket, though a couple of the springs weren’t under tension, so can move about a little. As I had an alternative basket with no play I fitted that as well as the later type basket bearing. Saw no other issues carefully reassembled. Checked the gearbox sprocket is tight on the shaft and the rear sprocket firmly bolted to the hub. And I still have my clunk.
So there’s about 1.5 inches of play when in gear measured on the circumference of the rear wheel, which is about 5/8” at the rear sprocket. Without something to measure that against not sure if that is typical or bad.
The only engine mod is I’ve removed the starter motor and the gears at that end of the cross shaft. The gear change is fine, clutch action is good and it’s fine once under way.
I know my way around an engine and everything about it says a clutch issue or something loose but damned if I can find it. Suggestions appreciated.

 

[5twins]

I had that little clunk on my '78 as well with the original clutch. I don't know what caused it. I "fixed" it by upgrading to the later 6 plate clutch inner hub with the dampened bottom plate. It engages smoothly with no clunk now.

 

[Barkstar]

I wish it were just a little clunk but I have a feeling it might be doing damage. I'll keep scanning eBay for a later clutch, though good used parts are few and far between in England.

 

[Jan_P]

Thinking out loud here

So there’s about 1.5 inches of play when in gear measured on the circumference of the rear wheel, which is about 5/8” at the rear sprocket.
I think that is about right

Has a start been tried in second or third gear...carefully .from standing ... releasing the clutch with the same noise.

 

[Barkstar]

Thinking out loud here

So there’s about 1.5 inches of play when in gear measured on the circumference of the rear wheel, which is about 5/8” at the rear sprocket.
I think that is about right

Has a start been tried in second or third gear...carefully .from standing ... releasing the clutch with the same noise.

Thanks. At least I know the play at the rear wheel is about right. I'll try starting in 2nd when the weather warms up a bit.

 

[Barkstar]

Thinking out loud here

Has a start been tried in second or third gear...carefully .from standing ... releasing the clutch with the same noise.

Finally got to check out how much slack in each gear and it is way more than 1.5" in 1st and 4th, more like double that.
So it looks there a problem lurking in the gearbox which I doubt is an easy fix and probably needs the cases splitting.

 

[TwoManyXS1Bs]

There's quite a bit of clearance in the transmission gears' dogs and slots. May not be the problem.

And, you've eliminated the clutch basket as the possible source.

This is a tough one.

Since you've been into the right side clutch area before, all I can think of is the kickstart gear, maybe mispositioned clip arm, possible not fully retracting, and doing a *clunk* when the countershaft's 1st gear starts turning and the kickstart gear fully retracts.

One test is to see if the bike can be rolled backwards, while in 1st gear, clutch pulled. A non-retracting kickstart gear will prevent rearward roll...

 

[Jan_P]

Thinking out loud
The mentioned -- it is way more than 1.5" in 1st and 4th, more like double that.
Is it significantly less on the other gears .. ???
The gearbox have good reputation and the power is not sot so high

Inspection from Down under --> ????
I have done that with good results on a Honda
connected to a Computer

Something like that
https://www.ebay.com/itm/6-56FT-Wat...459352?hash=item4d98a56a98:g:b0sAAOSw7ttcvguo

 

[TwoManyXS1Bs]

...Inspection from Down under --> ????
I have done that with good results on a Honda
connected to a Computer...

Yes, good one, member GlennPM was able to use a borescope to examine his transmission's functioning, in this marathon thread, which includes his borescope videos...

http://www.xs650.com/threads/overdrive-5th-gear-dropping-slipping-out-to-neutral.41539/

 

[Barkstar]

Thinking out loud
The mentioned -- it is way more than 1.5" in 1st and 4th, more like double that.
Is it significantly less on the other gears .. ???
The gearbox have good reputation and the power is not sot so high

With the bike on it's centre stand with it in gear in 1st and 4th the movement at the circumference of the rear wheel is 3 inches. In all the other gears it is half that, about an inch and a half. I understand that gears work in pairs, so I'm imagining that 1st and 4th are a pair on this box.

As has been said it is a puzzle because if something had broken in the box there surely would be other symptoms. I aim to take it for a run to confirm setting off in 2nd does avoid the clunk. But I got up this morning to falling snow, so it can wait. If this cold weather persists I may just check the kickstart mechanism as suggested by 2M.

Thanks for the input