Losing Clutch Only at Certain Loads?

Hello all, I have a weird one. 1971 Norton Commando...
I was riding when I tried to shift. It was hard to do so I pulled over. Hard to do meaning I was trying to move the shift lever and it wouldn't move. I realized my clutch wasn't doing anything. So, I tightened up my clutch with the handlebar adjuster and was able to use the clutch and change gears so I kept riding.

About 5 miles down the road, I go to shift, pull in the clutch, and the clutch lever just comes in as if not connected to the gearbox at all- no tension what so ever. I pull over, lugging the engine of course because I was in third and could no longer get into second or first. The clutch was so loose that even at it's tightest setting on the clutch lever it would not work. So, I do the walk of shame home (tow truck).

I get home, open that window on the primary side and adjust the clutch pushrod. I also opened the little window on the gearbox, initially it looked like this (this is an imgur image since I am not VIP on here, please cut and paste URL): imgur.com/a/0A6Yo . I adjusted the clutch pushrod so that arm inside the gearbox that attaches to the clutch cable was laying down as it ought to be with a tiny little bit of free play. Take the bike out and it kicks ass for a mile. Then same thing happens, push the bike home.

I was wondering if for some reason perhaps the nut that secures the clutch pushrod was coming loose. It was not. The nut that secures the clutch pushrod had NOT loosened on the clutch. But, I loosened it up and made even less free play, tightened the nut back down took it out again- just in case it maybe had too much free play last time.

So, the bike kicks ass for a quarter mile. I start going up hill in third gear, at 3200-3500 rpms, I go to shift, clutch is loose again as if not connected. I was close to home so I decided to just keep riding without a clutch to get home. Once the road leveled out, clutch came back. I went around again, clutch was fine until going up this little hill and the clutch was looser but still functional below 3,000 rpms. Once I was going up hill and hit 3,200-3,500 rpms the clutch would become so loose it was useless, then when the road leveled out and rpms dropped a little, clutch was fine again. After the road would level I could rev up to 3500 rpms without loosing clutch. Any ideas?

Thanks

Maybe the circlip holding the clutch basket on the mainshaft sleevegear is bend or broken?
https://andover-norton.co.uk/en/shop-dr ... alternator
No.55 in this diagram.
I had to grind down mine a bit on sandpaper so that it fits in the groove on the shaft.
When you order get a few of these. They are difficult to get in the right location.

Or the clutch operating lever slipped down in the groove of the operator body.
https://andover-norton.co.uk/en/shop-dr ... hift-lever
No 33 in this diagram

Thanks Rivera! I will take a look and follow up

Sometimes that situation is the circlip behind the clutch basket being worn so it will slip out of it's groove on the main shaft. It can give the lever the on and off again feel. If you remove the clutch basket to inspect the circlip, a sure sign that it's being displace is the marks left on the inner primary cover where the clutch basket rubs when the circlip jumps out of it's groove and the whole basket moves backward on the shaft....

The circlip is held in place by a washer with a groove in it to keep the circlip from expanding out of the groove on the shaft. When I had this problem some years ago, I just replaced the circlip because the washer looked good to me. I haven't had an issue with the basket since I changed the circlip.

Edited to add: Rivera beat me to it...

o0norton0o said:

Edited to add: Rivera beat me to it...

Click to expand...

Hah!

Thanks Rivera and o0norton0o!

Well so far I verified it is not an issue with the actuator arm being misplaced. So, next up is that circlip

Hey guys so I pulled the clutch, circlip looks ok to me and I don't see any marks on the inner primary. Any thoughts? Attached are links to the photos:
https://imgur.com/4YjtyL1
https://imgur.com/a/CQk4k
https://imgur.com/PEui3wF
Inner primary:
https://imgur.com/a/gFvUX

Look again carefully at the circle on the main shaft. The right hand end on your photo shows it is split, or going that way. I don't think it is bad enough to give the symptoms you describe but one thing eliminated. I believe some people fit the circlip fitted in the Mk3 electric start mechanism as it's supposed to be stronger.

The sleeve gear bush looks as if it's been working its way out but I'm not sure if that is the cause of the problem or not?

Can a nut on the other end of the mainshaft come loose and let the shaft and clutch slide over to the drive side?

Usually when the clutch locating circlip goes it's game over and clutch functionality is gone.
That's been my experience anyhow.

Triton Thrasher said:

Can a nut on the other end of the mainshaft come loose and let the shaft and clutch slide over to the drive side?

Click to expand...

Yes it can. It happened to me. Same problem as described here. Only problem was too late for a simple fix by the time I had sorted out the P.O.'s misadventures and the nut had become a bush plus filled the g/box up with metal.

I was 100 miles from home when the symptoms started so the nut flogged itself to death in that time.

Dereck.

Suggest you look now before the nut becomes unuseable and locktite that bastard in place.

Thank you, I will look. Thank you to all those who replied. I spent a long time working on this today. I will keep you all informed about what I find out

Well I found an odd thing. The clutch center nut was tightened only finger tight, and the lock tab washer was not bent to secure it. I tightened it to spec (70 foot pounds), reassembled... Now when I pull in the clutch, I can feel the center move (I have the clutch window open and can see and feel it moving) but the clutch does nothing. So, I've done the opposite of fixing the issue and made it worse instead. I can't understand how if I feel the clutch moving when I pull it in, it does not do anything.

Your problem is similar to mine. I found KNumb KNuts had put a copper washer under the l ock tab on the clutch hub. I obtained an HT washer and fitted that. It seemed to have fixed the problem but it did it again 100 miles from home. After rechecking again, The next fault found was the nut problem inside the gearbox mentioned above. That resulted in a complete rebuild of the gearbox.

Dereck

NjNortonCommando said:

Well I found an odd thing. The clutch center nut was tightened only finger tight, and the lock tab washer was not bent to secure it. I tightened it to spec (70 foot pounds), reassembled... Now when I pull in the clutch, I can feel the center move (I have the clutch window open and can see and feel it moving) but the clutch does nothing. So, I've done the opposite of fixing the issue and made it worse instead. I can't understand how if I feel the clutch moving when I pull it in, it does not do anything.

Click to expand...

70 ft. Lbs is a misprint. 40 & blue loctite seems the accepted norm. I know, whiskey... tango... foxtrot... :twisted:

NjNortonCommando said:

I tightened it to spec (70 foot pounds),

Click to expand...

OOPS, maybe it IS a sheared clutch locating circlip.

I recently wore out a mainshaft bearing (on the right side), and had very similar symptoms. If you can move the clutch basket in and out, that is the problem.

Mike B.

Might be worth considering a belville washer and loctite on the clutch centre along with a new circlip and 40ft/lbs

Thanks Dereck!