Clutch operation

I would be grateful for some advice on a clutch issue. I can select neutral easily from cold but as the engine and gearbox reach normal operating temperature, neutral becomes more difficult to find. I have made the adjustment at the clutch itself as per the manual, then taken up the slack at the handlebar. I have to adjust it to the point where the clutch pushrod is just rubbing against the actuating mechanism to get the required 'lift' to free the plates when hot.

I am using all the leverage at the bar to free the clutch and it engages very close to the handlebar as I accelerate from a standstill. I stripped the clutch recently, and all the plates are flat and were degreased thoroughly. I did the Mark 3 gearbox breather conversion. The clutch centre and hub are OK. Even directly after the rebuild, it was still the same. Is this common on Commandos? Also, I don't feel the lever snap back as it is supposed to. The lever action is reasonable, but from what I have read, it could be better. My clutch has the bronze plates, and it's an 850 Mark 1. I have heard that as the clutch wears, it needs greater pressure to disengage. How do I set up the stack height on a bronze plate clutch? Sorry to ask this as it has been covered before, but it's hard to find some of the relevant posts. Advice would be appreciated.

We experienced something very similar on a Mk3. It all seemed fine on the set up, but then we noticed that the plate and basket splines had wear notches which we had simply overlooked. Filing the waveiness out of them cured the problem. Not a long term cure, but so far hasn't come back.

Mick

Clutch

I am interested in the "Mk3 Breather Modification" mentioned - what is this ?

Cheers.

Re: Clutch

mwoo said:

I am interested in the "Mk3 Breather Modification" mentioned - what is this ?

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This is the breather modification: http://www.oldbritts.com/12_065199.html

Gearbox Breather

Thanks LAB

daveh said:

I have to adjust it to the point where the clutch pushrod is just rubbing against the actuating mechanism to get the required 'lift' to free the plates when hot.

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It could be worth checking that the lifter assembly parts are not worn, especially the roller, sleeve and pin? If there's any sign of wear, then I would replace them, along with a new operating lever. Check that the operating lever movement is exactly in line with the cable. It may be necessary to set the pushrod adjuster a little tighter than the manual recommendations, but there must be some freeplay.

daveh said:

Also, I don't feel the lever snap back as it is supposed to.

My clutch has the bronze plates, and it's an 850 Mark 1. I have heard that as the clutch wears, it needs greater pressure to disengage. How do I set up the stack height on a bronze plate clutch?

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An option could be to change the bronze plates for fibre ones, and then adjust the stack height?: http://www.oldbritts.com/ob_clutch_info.html

Your handlebar lever shouldn't really lag behind when you release it? So the cable may need re-routing or lubricating -or replacing?

Thanks for that L.A.B. I made sure to check the alignment of the clutch actuating lever with the cable, as per the manual, and the roller and lever seem in good nick. I probably wasn't explaining myself well but there is no lag when I release the clutch lever at the bar. When I pull the lever, there is no 'over centre' feel as the heavy fingers of the diaphragm are released, followed by the lighter fingers, if you see what I mean. Are the fibre plates known to be better than bronze? And is the reduced weight better for the gearbox?

daveh said:

there is no lag when I release the clutch lever at the bar. When I pull the lever, there is no 'over centre' feel as the heavy fingers of the diaphragm are released, followed by the lighter fingers, if you see what I mean.

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Right, I see what you mean, my clutch goes over-centre when the ball end of the lever is about half an inch away from the grip. I don't find the lever force excessive, so haven't bothered trying to 'tune' the stack height.

daveh said:

Are the fibre plates known to be better than bronze? And is the reduced weight better for the gearbox?

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Some owners have remarked that modern fibre plates are better, (less slip & drag) and there could be a slight weight reduction, but I'm not sure if it is a significant amount? I'm still using the bronze plates and they seem to work well enough if they are cleaned occasionally.

Take it easy boys.......I am sure BDM spirit is somewhere looking at us!
clutch weight should awake him.....that's a joke , just because I am missing him and his knowledge. Pierre

Butting in here...I know...but a clutch that gets grabby when hot...sure the old push rod seal conversion isn't called for? Another point is the leverage in the tranny where the cable hooks up to that little lever. If the bolt is worn out it will make for lousy leverage. Grooves in the Clutch center, as mentioned, causes the plates to not want to separate. My guess is the Dyno Dave trick though.

I take from LAB that I can stick with the bronze plates, provided they are cleaned periodically. I suppose it's no harm to install the clutch pushrod seal, in addition to the Mark 3 gearbox breather modification. And also, I should check that bolt on which the roller pivots in the clutch actuating mechanism.

I just finished my primary and trany rebuild. I degreased the clutch plates and roughed them up on the cement because I had some high rpm slippage. Slippage cured . I noticed my stack was not quite up to the clip groove and now I'm wondering as you if I needed to mix up some parts to get a thicker stack. I have a heavier clutch pull than I have seen and like. I can find neutral hot and cold. Perhaps you have something in your gearbox binding?(main or lay shaft gets hot and grows ,binding up not allowing the gears to be thrown) or a pawl spring that needs a little attention. Or ,I just thought of this, your primary chain is probably too tight, running OK when cold but when the primary housing expands faster than the steel chain it pulls on the clutch basket and binds up the trany inputs and outputs.

If your clutch lever feels heavy and never reaches the easier 'over-centre' inversion point which a diaphragm should do, then I suspect you need more stack height on the plates.
Check that all previous suggestions are ok and that the little roller toggle arrangement where the cable hooks into the gearbox is correctly built up and is in line with the outer cable entry position on the cover.
Hot drag and difficult neutral selection is also aggravated by a primary chain which is too tight, or excess end float in the kickstart shaft. Aim for 5 to 10 thou end float max. You can shim this shaft using rear isolastic shims.

Thanks Jimbo and Scim77. The easier clutch pull needs a check on stack height, which I will correct if necessary. I took great care to tension the primary chain correctly, so I know it's not too tight, but I wasn't aware it affected neutral selection. I had the bike out today, so after a good run, when neutral was hard to select, I disengaged the clutch with the engine off, in first gear. With the adjustment at the lever to the point where there is almost no clearance in the clutch actuating mechanism, the bike would freewheel only when the lever was almost at the bar (less than 1 cm away). I have an average sized hand, and the lever is almost at my fingertips when at rest, so it seems like I'm not getting the required lift to free the plates. I cleaned the plates thoroughly about 600 miles ago. Does that point to the actuating mechanism, as LAB and others have remarked?

Thanks for the replies , . I had to this point assumed it was the original bearing but having just pulled the clutch apart and found 5 friction and 4 plain plates i now wonder what other mods internally have been done as the 750 only had 4 friction and 3 steel according to my reading. If its been upgraded to a 850 clutch maybe the bearing has been done also. If i have to pull it apart to check its the same as replacing job wise i guess so thanks in advance for the assistance i will rewuire,, Theres about six weeks of winter left here so i better make a decision ASAP

Cheers

Dave
Check your diaphragm spring. It's not often mentioned but they do warp and after years of trying to get my clutch to release cleanly with all the mods, correct parts etc I found the fingers were different heights. You can check this with the spring off and tool removed. Any significantly uneven finger height will affect even release. I replaced the spring and problem solved. I do not however adjust to the manual. One turn back from touching the pushrod is a lot of play to take up before the clutch operates. I screw in adjuster and back off 1/4. You should find that when hot the hand lever play increases, well mine does and it does make sense.

Keith — I have the diaphragm spring off at the moment, so I will check this. I too thought that one full turn out of the adjuster nut is a lot, so I turned it out 1/2 a turn, but the clearance at the handlebar lever still becomes smaller when hot, unlike yours, which does the opposite. I will get to the bottom of this! Thanks for your advice.

I figured that with the aluminum cases expanding faster than the steel gears and misc parts it explained the increased hot clearance. I have a belt drive and knowing the drum expands a lot diametrically it probably does the same axially. Come to think of it I don't recall it happening with the original steel basket. Sorry to confuse.