clutch and gearbox help

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Jan 10, 2006
Today I've been for a ride. From the start the engagement of the first gear has been quite noisier than usual. On the other hand, I've noticed that the clutch seemed to "wait" a second before engaging, making a slap noise everytime I changed gear. I've just adjusted the clutch and still does it. The only thing I can think of is that I've tensioned the primary chain and maybe I've done something wrong (could this have anything to do with it?).

Thanks for your help, mates! :wink:

Maybe the primary chain tension is now too tight. This will sort of pull the clutch out of shape and shorten the gearbox bearing life. The primary should err towards the loose side, the 3/8" slack on the top run needs to be checked at many points not just one area.

My suggestion is re adjust and looesen first to see if this cures your clutch drag.

Cheers Richard
Tension on the primary chain can be pretty tight without causing problems....although it should perhaps be set a bit loose as suggested above....but if the clutch center teeth have groves/notches from the plates banging against them for years....the plates will catch in the grooves they have made, and the clutch response will be somewhat unpredicable...the plates will all of a sudden move out of the groves, and slam into place against the plate next to them....makes for jerky starts...check for groves on the clutch center, if they are to be seen, you can carefully file them flat and it will make the clutch smooth again, and then perhaps order a hardened cluch center and build it in when you have time....

With regard to HeWho, your comment about obtaining a hardened clutch centre. Does this mean the original is not hardened?
I have just taken my clutch apart (because of drag at the wrong times)and found the centre has notches worn by the plates. I have access to a good used centre but if this is not hardened then a new one should be used?

I have used an unhardened center for 30 years, and never done more than file/dress it a couple times...I would be happy to buy a hardened one...but it costs money, and I'm a cheapskate. A good used one will be fine, until you wish to invest in a hardened one, the original ones are not hardened to my knowledge. Main point, get rid of the grooves and you will be happier with your bike..... :D
The hardened clutch centres were introduced at the same time as the bronze clutch plates to deal with the harder material of the plates, if you are using fibre friction plates then the unhardened centre should suffice. If you have to buy a new clutch centre anyway it would be prudent to buy a hardened one and I suspect that this is all that is now available from most sources.
Today I've been adjusting correctly the primary chain and nothing improved. I'm taking Hewho's advice (as I've done other times before ;))
and I'm getting a new hardened clutch centre from RGM right away. I'll let you know about my progressions.

Thanks a lot, dudes!
look at the clutch center before you invest the might be able to be filed and that will hold for a long time....sure the chain isn't TOO loose? Loose enough to whip and slap the chain case?
Yes, chain has now a correct tension and the clutch isn't still fine... I suppose I can use the bike to take it some 30 miles away to get repaired or should I call a pick-up truck? :?
You will have to decide that.....I'm not there and I can't really see what is going on with the bike. If it is just a jerky clutch and not some awful thing like a bearing that is falling to pieces...then you can drive it there. You have checked the bearing...haven't you? This is all quessing until you take the clutch apart and look at what you have.... :wink:

PS...there is oil in the tranny isn't there...or?
It sounds a bit obvious, but pulling the gearbox backwards to tension the primary chain will of course slacken the final drive chain. You have checked that haven't you?

Other areas could be sprocket condition or rear hub cush rubbers. If everything at the power unit end is up tight then the rear wheel area is perhaps the next place to look. Grab the rear wheel good and hard with the bike on the mainstand and see if you can feel any backlash.

Was there any transmission roughness during normal running ?
All chains have been checked and hub cush rubbers are new... It's something to do with the clutch I believe. During normal running everything seemed fine, also when I reduced to lower gears it seemed to be fine, except to find neutral and to engage first gear, and that "slap" sound I described everytime I pulled the clutch back...
Just a thought, but is the clutch sitting properly on the shaft with that horrible little earless circlip located in it's groove and in the counter-bore in the locating spacer ?

If the clutch can move in and out on it's shaft then that would give a delayed take off, I think. It would also produce the drag that causes poor engagement because you would not get full lift.
Well, I just took off the plates to get them cleaned and put the whole thing back together again the same way back... I'll check it up tomorrow if I find the time and see what happen.

Thank you, 79x100! :wink:
Good Luck Sparkplug,

The circlip can and does mill itself away against the splines so it could just be co-incidence. Tightening the clutch centre nut can also cause it to move if it's worn as it no longer has a nice square face to bear against.

If you haven't looked at it before, you'll be horrified how that tiny clip has to take the full 70 lbs/ft as you tighten the centre nut. That said, if it's in good condition it can't go anywhere.
On stock bikes that I have worked on the trans is always twisted out of line with the motor crank. A chian drive primary dosn't seem to care but it costs lots of power. Most people leave the bottom trans mount bolt too loose after an adjustment. This allows the case bosses to wear in a crooked way that leaves it very hard hold it straight after getting it right. Frank at clubman racing stocks the dual adjuster set up this really helps hold it straight and is a must for belt drives.
79x100 said:
Other areas could be sprocket condition or rear hub cush rubbers. If everything at the power unit end is up tight then the rear wheel area is perhaps the next place to look. Grab the rear wheel good and hard with the bike on the mainstand and see if you can feel any backlash.

You know what?

You were right! I had seen a big spider net in my rear wheel but just thought wow, what kind of spider could have done this? A well fed one I guessed... :?
It was the remains of my disintegrated-non-existant-anymore rear hub cush rubbers!! :shock:

Is there a special way to place them?
How can all this have happened?...

Thanks again to you all, specially 79x100. :wink:
Hello Sparkplug,

Glad to hear that it sounds like the least expensive option ! :D

Probably just a combination of age and heat. (Had the bike been standing for a long time ?) Chemical contamination could also be a factor - WD 40 or modern fuel used as a degreaser.

The rubbers come in "thick" and "thin" so you need to place the thick ones where they will take the driving load and the thin ones take the backlash.

It would also be a good idea to check wheel bearings, especially in the drum. I imagine if it was sloppy, the rubbers would have to cope with additional movement that they weren't designed for.

Lets be honest though, the whole cush-drive thing was a bit of an afterthought. After years of faithful service, the old bolt-up hub was deleted because they failed to fit a shock absorber in the Commando clutch. :)
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