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Dominator88 clutch

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Hello all,

i have a perennial problem with neutral selection . When the engine is not running neutral selection is easy. Start the engine and neutral selection is just about impossible from either first or second gear. Even slowing to a junction in second neutral will not engage while on the move at a walking type pace! The machine is fitted with a Bob newby clutch and a mick Hemings 5 speed gear box. The clutch runs true any clues would be much appreciated.

regards DAVID

 

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Hi David,

Here are some of my 'brain dump' thoughts/suggestions:

Engine idle speed too fast?

Detent 'notch' on gearbox cam plate not deep enough?

Wrong profile plunger?

Plunger spring weak?

Primary and/or final chain slack?

Clutch not releasing enough? (especially if you have the laydown box). 

Wrong oil in the gearbox? (Oh no! here we go again...)

'Correct' clutch lever?

You say a perennial problem. Have you only ever had the bike with the 5-speed box and Newby clutch? If you did or had the conversion done, was it ok beforehand?

 

Regards,

George.

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First check.  Remove enough chunks of Tinware to get at the clutch basket. Grab hold of the basket and give it a good pull and push. If the basket moves enough to make a click or by a significant (say 20thou) amount then either the basket bearing is worn or loose or the mainshaft bearings need replacing. Any of these in poor condition will make selection of neutral more than interesting.

Second check. Take the clutch plates out and check them all for being true. Any pretending to be bananas will also make selecting neutral hard work. 

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I did everything listed and suffered the same issues for years. Then when the clutch was off noticed that the back of the clutch (in fact the spider) had wear marks from contact with the sleeve gear of the box. I angle ground metal off the spider till there was clearance. Soon I found the problem returned and after much carefull inspection found the clutch was migrating along the box shaft due to a poor register (shoulder) in the spider.A new Better designed spider solved that one.I found that the clutch drum to have more wobble than I liked. A set of 1thou oversize rollers cured that. I now set up the springs with a dial guage and find the clutch will do everything that yours won't. A tight primary chain will ruin all.Burrs on the box shafts and inside the gears also helped make a stiff change 2nd/3rd. Its a dream now (till something else turns up). To check the spider clearance I had to totally dismantle the clutch and then bolt up the spider on its own on the shaft.

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hello, the first lot of comments may of hit the nail  the weak plunger spring for the selector cam  its underside of the gearbox   at the front  check it first  and then proceed with the clutch its self checking for burs and check the condition of the centre rubbers  where the spider lives  now to change out these rubber you need specialist tools  like what I made for this job   without them you have a very hard time getting new rubbers in without destroying them first, and change the centre nut at hold the clutch on centre nut threads wear    that's  all I have to say Yours Anna J  

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Thankyou all,

everything is new clutch,belt drive and gearbox, I couldn’t compare with the laydown box or the clutch that was their because they were both b,,,,,,,,,,, hence the change to a more modern system, this is now a different sort of not working properly but now I have much to check.

thanks again

David

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On a chain drive ,as everything heats up the chain tension tightens, will be the same on a belt drive,   too tight?.

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David, 

Is yours a laydown box, and I assume the clutch is a Commando style one? If so, there have been several questions on the forum about not getting enough lift with that set up and how to resolve it. It should be worthwhile doing a search with something like 'clutch lift'. 

Regards, George.

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hello now older gearboxes like the laydown use a three-part push rod and a ball in the centre and the end part to push the clutch open is a mushroom type rod  now the commando clutch doe not have these parts so that is were to start looking at first and maybe you need a push rod modification so see RGM motors  ask  Rodger Yours  Anna J     

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The operating lever and cam are different for a Commando because of this problem. The commando setup has a longer lift.

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But David also says he has a Newby belt drive, and these come with a 'Commando' clutch.

Laydown box clutches, I believe,  had one less plate than later ones, and therefore didn't need to lift as far? This gives the issues that David is now experiencing. 

There was a thread quite recently that went into all the lift heights that each 'box could give. You could well be right about clutch/sleeve gear contact too. I'm pretty sure the answer to the problem is now one of those two. 

Regards, George 

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Hi again,

The Bob newby clutch fitted with the belt drive was bought specifically for my Dominator 88 but I guess that means nothing really and I think the lift idea is probably on the right track for my problem. Looking through the inspection hatch of the gearbox when the clutch is at rest the arm is only just clear of the casing, when the clutch is pulled in it travels a fair way towards the other side of the casing however their may be room for improvement. If I loosen off the centre nut on the clutch that holds the pushrod in so that the clutch lever has play it doesn’t need to be undone very far for the arm in the gearbox to drop off the ball as it were and then of course no lift is possible at the clutch at all. It’s all a puzzle, Mick Hemings assures me that the arm is set correctly. I will attempt to take some photos but technology is not one of my strengths so posting them may take some time.

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So you have a 'normal' clutch, not a Commando type. So, that being said, how many plates are in it? The 500's had one plate less than the 650/750's. The more plates, the more lift required. Might  be worth a try removing one of the friction plates? With luck, there will be enough friction to allow you to start it. Then, when you pull the clutch in the plates will separate further, with less drag. At least it will give you a clue as to whether the clutch is the issue or not.

The answer is there somewhere.

Regards, George. 

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Hi George, it’s interesting what you said about the removal of a plate and I’ve done that this morning, obviously I’ve had to remove the smooth spacer plate as well which both together amounted to just over 11mm. It has made a marked difference in that neutral is just a click away at a slow walk. At a stand still it’s still very difficult and is best done with the hand ( my ankles must not be robust enough). This may be due to to newness of the camplate however and not a weakness of an ankle. I’ve done all that I can do to this machine and spent something like£18 k on it including the initial cost so I think now to move it on and start some other projects lined up. It’s had a JMC engine rebuild, new wheels,tyres , twin leading shoe brake, new rear brake drum,chain, BTH mag, Bob Newby clutch and belt drive, Mick Hemmings complete 5 speed gearbox, indicators. The paintwork is very smart although not perfect and it’s slightly incontinent which is it’s only fault.  Thanks again for your help.

david

 

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The gearbox internal lever is not lined up with the cable entry ,and something else in there is bothering me, have to look at mine!.

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Looked at mine, Davids assembly is correct ,but the cable line is out enough to make the action heavier than it need be.  For a really sweet clutch its the addition of many small  carefull adjustments (none seemingly important on their own) that add up to bliss and that lovely quiet one finger click into first gear.  Its taken friggin years for me to get there!!. Perhaps I should open a Norton clutch clinic,but then I would have to  work on those  AMC Comdom things !!.

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My Belt Drive conversion is an RGM kit. I have now covered around 5000 miles on my bike and it generally has been fine apart from one small issue.

Twice I noticed the clutch lever gain more than 1/16" of free movement. Originally I put this down to the cable stretching but it turned out to be the result of the gearbox mainshaft nut coming loose. Fortunately the locking tab held everything together but to have it happen twice running was a bit of a surprise. This nut was torqued up to the 50 lb ft as specified.

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Its not possible to tell visually but that belt looks tight. Rule of thumb is you should be able to twist it 90 degrees with your fingers. As Bob says...it all adds up.

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Something is still bothering me!,looking at your photos  the travel of the gearbox lever appears excessive  compared to mine . No idea why though. I assume that the super dooper new clutch has a much better bearing race than a std norton ,as a tight belt (when hot) will pull a drum out of true to the clutch center and drag the plates. Sometimes leaving "witness" marks around the inside of the drum where the edge of the plates rub.This action drags the center ,speeding it up and making neutral selection hard. On a std clutch I fixed this by reducing drum wobble (bearing) and angle grinding (!) metal off the outer edge of the Probably pattern plates.

Hi David

2 clutch pressure plate adjusting screws available (if Bob Newby uses same thread):

040360 short 5/8"

061179 long 7/8"

Nut 040376 / 060005

Hope this helps.

Tim S

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Thankyou all again,

ive not made a lot of headway with the clutch problem but have found by the removal of a plate as suggested that neutral is easier from a walking pace but still almost impossible from a standing position. The only thing I had to do was shorten the pushrod a tad to allow the adjuster to screw in sufficiently. A friends Dominator has a different fulcrum point on the lever which makes it very light in action so that will be a next step. Not that that will help with neutral selection but the clutch will feel nicer for it.

regards DAVID

 

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