Clutch play ES2

You've got it George. What is surprising is the amount of extra clearance at the lever that occurs....you wouldn't think the plates could expand that much after all they are very thin and the temperature can surely not have risen much above 100 Deg C, but the amount is magnified by the leverage ratios of the bar and gearbox operating levers... Another part of the process is that as the clearance is initially increased all further clutch withdrawals are not fully disengaged so you are in fact slipping the clutch continually at rest which creates a runaway snowballing* action and more heat is generated and so on.

What you can do, and it's pretty easy on the Laydown gearbox if you have the correct finger wheel adjusters fitted to the cable, is to simply stop at the first sign of the lever's clearance increasing and turn out the gearbox end cable adjuster to compensate and take up all the new slack which will make sure full release of the plates is still occurring and stifle the runaway heat build up. Of course when you are out of the jams and running freely again you will have to readjust the cable slack but this takes only seconds apart from the quick kerb side stop to do it....not recommended as you ride unless you have arms like a gibbon.

* Perhaps Fire balling!

Les

PS: might be a good idea to fit a cable adjuster at the clutch lever end so you can adjust it on the move

Just out of interest what is the distance between the pivot and cable nipple on your clutch lever? I understand fitting a 7/8th gap makes the clutch much lighter and I think any free play caused by heat would consequently be less than on a more standard 1 1/16 pivot gap?

dan

I'm trying to buy a pair of 7/8th levers but can only find them at Norvil for about £40 a pair. They make the clutch lighter although there's less movement in the activating rod

dan

Dan....The 7/8" lever will make the clutch:

1) Lighter.

2) withdraw the clutch pressure LESS because of less movement.

3) actually suffer worse by moving off MORE from its normal gap clearance when the clutch heats up.

The 3rd point is less easy to visualise. But a smaller radius at the lever pivot creates a smaller circumferential pull movement. When the clutch expands and increases the slack, any unit of cable slack appearing at the lever end will result in a bigger amount of turn or gap being created with the 7/8" lever... The 1 1/16" type levers will be less affected by a clutch heating up as the total operating circumference (pull) is greater so any change will be proportionally less.

Les

PS...One, perhaps not too practical, way to get the benefit of the 7/8" lever with its lighter pull and to negate points 2 and 3.... is to bend the lever forward. You will have a much lengthier range of leverage but it may be too much for some to stretch their fingers that far to use easily.

Les

7/8" ball and non ball ended at decent price?

http://www.ebay.co.uk/itm/407P-DOHERTY-TYPE-BSA-TRIUMPH-NORTON-7-8-CHROME-PLAIN-END-CLUTCH-BRAKE-LEVERS-/272289596512?hash=item3f65b98460:g:83AAAOSw-dBTuTPl

http://www.ebay.co.uk/itm/208PA-DOHERTY-TYPE-BSA-TRIUMPH-NORTON-7-8-CHROME-BALL-END-CLUTCH-BRAKE-LEVERS-/232044412516?hash=item3606ecbe64:g:KD4AAOSwFL9TuVd~

The primary chain tension changes as everything heats up ,and a tight chain will cause drag which will heat the clutch and cause slack . 7/8 pivot levers (AMC boxes) if worn at the pivot can lose some travel and there is not much to spare. A really slow tickover will help reduce drag action into the box and aid neutral finding. My 99 has had a poor clutch for years despite loads of attention, Tollerable now but still room for improvement.

Les

you're right on point 3, me not thinking properly, but sadly the two levers you posted links to have 1" pivots!

I would rather have ball end levers as mine is currently at least a trials bike!

dan

Hi Dan...Oh dear...I never read the adverts properly....Yes the 7/8" refers to the bar diameter. Looking again for some, I note that ball ended with 7/8" pivots ARE difficult to find....

Les

I think 7/8"pivot centres is standard forNorton on the1950's bikes, (Triumph have the 1" centres), Ipurchased mine from FEKED

http://www.feked.com/handle-bars/handle-bar-levers/page-3/

and to get have a greater arc on the lever to get maximum plate lift, I ground the face of the lever back, almost to the nipple hole. This makes a reasonable lift with light clutch cable pull. A nylon lined outer cable will make it even smoother.

Thanks Paul, sadly they don't have ball ends, I'm trying to get hold of Feked to see if any of their levers that don't have the pivot distance listed are 7/8th ... they are going to call me back.

These are the only ones I have found http://www.ebay.co.uk/itm/BSA-BANTAM-BRAKE-LEVER-CLUTCH-LEVER-DOHERTY-7-8-FITTING-UK-MADE-/322090789348?hash=item4afe1b69e4:m:mOHsv_awly0pAxTBLh829pg but are a bit expensive..... but at least they exist!

They called me back, these are the right size - Ive ordered a pair!

http://www.feked.com/amal-replica-brake-lever-7-8.html

Will report back!

Nah George, you haven't seen the size of my hands!!

Sorry George I hyjacked your thread a little!

dan

These work too. Never tried them on a Norton though.

https://m.youtube.com/watch?v=9zSevtXlT5U

for sale here

http://www.ebay.co.uk/itm/UNIVERSAL-MOTORCYCLE-EASY-PULL-CLUTCH-MX-ENDURO-TRAIL-SM-/172267946713?hash=item281bf842d9:g:820AAOSwDk5UDiRQ

Dan

Hi George...It makes no difference at which end the cable slack is adjusted or varied at. I mentioned the gearbox end as the original levers did not have adjusters and the screw was at the gearbox. Nowadays owners use the wrong levers (it doesn't matter of course) so you end up with two adjusters.

Note however that the initial cold adjustment should still be done with the full correct procedure by either doing the clamp on the operating spiral inside the gearbox (Norton Box/clutch) or the centre nut and bolt on the pressure plate on the AMC box/clutch

Les.thatexplains a lot for me, I have an AMC gearbox and Norton clutch, as a consequence the only adjustmentI could find/make was via the cable, having said that it changes gear beautifully and no clunk selecting first! I guess I need to find an AMC clutch centre plate as I think they are interchangeable with the Norton ?

The Doll's Head and the Laydown need the 1 1/16" pivot centres as the worm on these boxes is pretty 'slow' and there just isn't enough lift with 7/8" centres. The AMC box has an operating cam intended to provide the lift but it doesn't make for such a nice action. I struggle to see it as an improvement.

The pressure plate on the AMC clutch has a centre adjuster for push-rod free play which the Norton clutch doesn't need as it is done at the other end. I don't think that the AMC plate will fit under all of the earlier chaincases.

Doesn't one of the Roy Bacon books state that the mushroom on the earlier box helps the plate to lift squarely ? I can't quite see that though.

Sorry I meant to say pressure plate, mine being a Norton clutch has no adjuster, but it's fitted onto an AMC box, I use the cable adjuster at the moment to adjust the clutch. I'll try one of these unless anyone knows better, http://www.rgmnorton.co.uk/buy/alloy-clutch-pressure-plate-holds-springs-buckets_877.htm or perhaps have a look at Netley. I think there's enough room in the chain case, I think it's a later one.

I guess they would have different numbers given one has an adjuster and the other doesnt, but I'm pretty sure I read that they are interchangeable in terms of fit. I'll try and find it.

dan

Dan...I'm not absolutely sure the springs and their holders of the Norton Clutch are interchangeable with the AMC alloy pressure plate.

What you might consider is simply drilling and threading your Norton pressure plate centre and fitting the AMC centre adjuster screw and lock nut. Another change will be that your Norton "mushroom" end part of the push rod will need to be discarded and the longer single length AMC push rod installed bearing in mind the new centre screw adjuster has a fair range of thread.

Les

Les .... God idea, much cheaper too! But I did find this which was where I got my info, many thanks to George Cohen RIP,

The AMC clutch was a re-design of the old Norton clutch. Dimensionally, it is the direct replacement and the two are interchangeable. But the internals are quite different. Whereas, the Norton has inserts in the chain-wheel and externally driven friction plates, the AMC is exactly opposite. The chain-wheel is solid and the friction plates driven internally. This was an improvement over its predecessor, especially in racing, where the old Norton clutch had some shortcomings. So although the two clutches are identical externally, and completely interchangeable, the components are not, with the exception of the pressure plate, which is pressed steel on the Norton, and alloy on the AMC. You can use the AMC pressure plate on a Norton clutch, the only advantage is that it won't rust when you run with open primary drive. The AMC was fitted to all the big AJS, Matchless andNortonswhich used the AMC box from 1957 right up to the Commando. Either clutch will fit any Norton or AMC box from 1934 to 1978 including Commandos.

When setting up the clutch, it is extremely important to make sure all the plates areflat, any bent ones should go in the bin! Make sure the securing nut is tight; use a clutch holding tool. Make sure that all three springs are the same length and strength. When fully assembled, with primary chain on, and machine on stand(ie rear wheel in the air ); put into first gear. Pull in clutch lever, and spin rear wheel. Note if the pressure plate is liftingevenlâ?..if not adjust the appropriate spring. Always allow free play on cable( to avoid drag ), especially with races which have clutch starts. Good luck.

Dan, I've mailed you. I think that I can help you out with the AMC pressure plate parts.

Hi Dan....seems most parts are interchangeable then but what is a surprise is that George Cohen says the Norton Pressure dome is made of steel.....I could be losing my memory but I'd swear my one is in aluminium....anyway looks like Richard has a spare AMC one for you.

PS I'll leave what I wrote above but slowly the image of a steel Norton Pressure plate is emerging from the depths....yes I'm pretty sure it is steel now...ah well........

Les

I know that feeling Les! My Norton clutch pressure plate is def steel, I saw mine a few weeks ago!

i should add that my 7/8" pivot levers arrived from Feked today - great service - £25 delivered, I've fitted the clutch lever and the difference is noticeable.

dan

This is a Norton steel pressure plate on an AMC clutch (friction back plate but not visible in the photo of course). Ignore the odd adjuster screw heads, they are a modification to use Ken McIntosh's matched springs.