Gearbox refurb

1970 S 750, I have just put a new clutch in the bike ( five plate) and despite all the adjusting I now find it tends to stick in gear and is hard to change back 4>3>2 especially if i am at a reasonable speed SLowing right down it will change back easily enough, I am sure it is a clutch issue as there was no issue before i touched it ,but even adjusting to the point where clutch is slipping to ensure it is totally free it still does it, Any suggestions on this mater appreciated but i have also decided to pull the gearbox and do the layshaft bearing which brings me to my question

While its apart is it worth the extra money to do the bigger refurb as i dont really want to pull it down in another six months, I dont mind spending but dont like wasting , The only kits i can find are from Norvil and i have pasted the info from their site. It seems the short kit has really only the bearings i am after, The Orings,seals ,gaskets can be obtained or made locally much cheaper ?so should i just order the bearings (maybe even they can be replaced at my local bearing supply shop. Gearbox has 5000 miles(original on it ) and apart from first paragraph i have no issues at all with it
Thanks in advance for your suggestions/advice. As always it is greatly appreciated

AMC - £105.00 Each
Kit Includes The Following Parts:-
1 x 1st gear bush, 1 x 2nd gear bush, 1 x 3rd gear bush, 2 x sleeve gear bushes, 1 x layshaft bush, 1 x sleeve gear bearing, 1 x layshaft superblend bearing, 1 x mainshaft bearing, 1 x kickstart spring, 1 x kickstart pawl spring, 1 x gear lever return spring, 1 x gear lever ratchet spring, 1 x inner cover gasket, 1 x outer cover gasket, 1 x inspection gasket 1 x gear lever o- ring, 1 x kick start o- ring, 1 x ratchet spindle o- ring & 2 x quadrant o- rings.


Short AMC - £40.00 Each
Kit Includes The Following Parts:-
1 x sleeve gear bearing, 1 x standard layshaft bearing, 1 x main shaft bearing, 1 x sleeve gear oil seal, 1 x inner cover gasket, 1 x outer cover gasket, 1 x inspection gasket, 1 x gear lever O ring, 1 x kick start O ring
1 x ratchet spindle O ring and 2 x quadrant O rings.

forget the kits. the parts i would look at are. superblend layshaft brg. 4th layshaft gear, 2nd pair (main-lay) 1st pair (main-lay) 1st main more so, kick start pawl, shift ratchet pawl spring, shift return spring, sleeve gear bushes (update to mk3 type) clutch release roller and bush, than your gaskets and seals. the sleeve gear brg. gives very little problems along with the main shaft brg and other bushing's. also look at the kick start shaft spline. the gears mentioned are known for tooth face spalling.

windy

Rockyrob, with regard to the sudden onset of difficult gear changes, are you sure that when you did the clutch that you did not re-adjust the primary and final drive chain too tight as either or both of these chains being too tight can produce the symptoms that you have :?:

Your spot on Reggie , I did adjust the primary. its now slack i would think ( 3/4 inch play) The chain seems to be ok , tho if the primary is slack does it by default tighten the final drive?

If they're both slack, I don't think that this will be the problem, but have you checked the chain tightness in various positions by cranking the primary chain say 1/4 of its run a few times and rechecking as there could be a tight spot, and the same with the final drive chain :?: With the final drive, it's best to check it with the wheels on the ground and with somebody sat in as well if at all possible.

Also are you absolutely sure that the clutch is not dragging as this is the usual cause of difficult gear changing.

Almost certain it is not dragging , I have tried various levels of adjustment , There is just the slightest free play in the lever in the outer gearbox cover when the handle bar lever is fully released, One thing i notice is that when fully released (hand lever) it doesnt spring out quickly, but rather slowly and the last 1/4 inch or so i actually have to push out with the back of my finger. If i dont do this there is no play in the actuating lever in the gearbox. New cable, clean push rod, all seems well so not sure why this happens or if its causing the problem, I imiagne if i adjust it to no play in the gearbox outer cover at all the clutch would be at point of slipping?

Rockyrob said

There is just the slightest free play in the lever in the outer gearbox cover when the handle bar lever is fully released

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I assume that when you are initially adjusting your clutch that you are using the push rod adjuster and locknut, No.49 & 50 in the diagram on this page http://www.nortonmotors.de/ANIL/Norton% ... 08&Part=49 as the amount of free play in the lever in the outer gearbox cover is not used in the adjustment of the clutch.

To adjust your clutch, back off the cable adjuster on the handlebar so that the cable is slack, loosen the clutch adjuster nut 50, screw in the pushrod adjuster 49 until it contacts the push rod, back it off one complete revolution (I use just over half myself), tighten the locknut up, and then adjust the cable at the handle bar until there is a slight amount of free play in the cable.

Rockyrob wrote;

One thing i notice is that when fully released (hand lever) it doesnt spring out quickly, but rather slowly and the last 1/4 inch or so i actually have to push out with the back of my finger.

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This is not normal. There are a few reasons that this may occur and possibly more than I am listing here;
1. If the cable is trapped or has a very tight bend/radius in it,
2. If your clutch centre is notched and the new plates are catching on the "notching" as they are running at a slightly different position to your old plates.
3. Are you using new fibre plates or sintered ( also known as phosphur bronze) as I note that you have said that you have replaced 5 plates. There are 5 plates on a phosphur bronze clutch and 4 fibre plates on the earlier type clutch. I have had new fibre plates which have been faulty as they were a tight fit on the clutch centre, and would not slide very easily.

Rockyrob wrote;

I imiagne if i adjust it to no play in the gearbox outer cover at all the clutch would be at point of slipping?

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Although you don't use the free play in the lever of the outer gearbox cover to check the adjustment, on a clutch that has the cable and pushrod adjusted correctly, there would be very slightly perceptable movement in the lever....I think. Basically, you check for free play in the cable at the handlebar adjuster.
I don't know if any of this helps :?:

I hope I haven't just tried to teach Grandma how to suck eggs

Thanks for the info Reggie I am basically doing the adjustment in that sequence. I guess the reason i concentrated on the free play at the gearbox outer casing was that if there was play there then the clutch must be fully engaged(disengaged?) giving me a starting point to work from, I will adjust per your instructions, The plates are barnett fibre sections, ,not the entire plate is covered . I didnt notice any binding putting it together but i will pull it apart and check. Thanks for your assistance

Whilst you're at it, you could make sure that the clutch operating lever in the gearbox outer case is properly located on the operation lever body, as they can drop, and still work to a point, but with reduced lever movement as I recall, but as yours seems to work reasonably well, I doubt that this is the cause.

If the clutch centre is not significantly notched, the plates will slide freely, the pushrod moves freely, the operating lever is properly located, and the inner cable is free to move in the outer cable, and the handlebar lever is not damaged on the pivot i. e. is totally free, with the diaphragm pressure, the handlebar lever when released should come to its resting point immediately.

Also to check if the clutch is releasing properly, simply pull the clutch in and see if the kickstart is absolutely free.

After this, I'm puzzled :?

If the clutch centre is not significantly notched, the plates will slide freely, the pushrod moves freely, the operating lever is properly located, and the inner cable is free to move in the outer cable, and the handlebar lever is not damaged on the pivot i. e. is totally free, with the diaphragm pressure, the handlebar lever when released should come to its resting point immediately.


Check ,check and double check , all as above, yet clutch handle does not retract, Looking at diaphram spring it goes over centre then doesnt come back, I think i may have stuffed the spring if thats possible , a home made spring compressor and lack of knowledge caused me to hyper extend the diaphram. as in fingers over centre half an inch or more, it sits flat but maybe the flex is not as it should be, I have ordered a new one asI can see no other possible cause

Are you sure that there is not an issue with the clutch plates, the plain or the new Barnett plates. Are they definately free to slide along their respective splines. I ask this question as I had a new set of fibre plates that came with my Norton, and when I tried to fit them, they were an interference fit on the splines, and would only slide on the splines with pressure. I don't think that they would have released the clutch, and so never fitted them.

You say that your clutch was working OK before you put these new plates in, can you not retro fit the original clutch plates and see if the problem remains or is resolved :?:

< it sits flat but maybe the flex is not as it should be, I have ordered a new one asI can see no other possible cause>

this sounds like a stackup hight issue. if you have the stack up to high you could have the spring over center.

windy

Along the same thought as Windy, you mentioned you installed a five-plate clutch. You have a 1970 Commando, which would normally take a four plate clutch unless you are also using the thinner pressure plate required by the five plate unit. This would definitely cause stack height issues.

Thnaks for the suggestions When i pulled the old plates there were five so I assumed PO had converted to a 5 plate clutch. There is definalty no binding on the splines, filed and smoothed just to be sure. I did notice when i pulled it apart after riding some 30 miles with new clutch plates that the outside of the friction plates appeared untouched, , the 2 outer plate outside surfaces were actually not marked at all. Stack height has me a bit confused I tried it with 5 plates which puts them nearly level with the circlip groove which then makes it go over centre and not return, Then i treid with just 4 plates which gives plenty of room before circlip but still with the same result, The idea of putting the old plates back in had not occured to me. thanks for that I will give it a try

I have stacked my clutch so that the pressure plate only just sits below the circlip groove, almost making it difficult to get the circlip back in, giving me a very light clutch, so I would be suprised if that was the cause Rockyrob.
Rockyrob wrote

which puts them nearly level with the circlip groove

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