I am posting in the hope that someone might know what is what with Norton gearboxes and give me some reassurance regarding the mainshaft and clutch centre fixing. If nobody knows, as they say, then no problem as I will carry on as it is. It is a 1950 plunger ES2.
First some background: the laydown gearbox has a different method of clutch centre fixing, and clutch actuation, from the later AMC style box. There are no pictures of the clutch attachment in the 1950 Norton Manual nor is there a diagram on ANIL's website. The clutch centre is held on to the mainshaft with a large nut (7/16W hex but most likely cycle thread). A mushroom headed push rod extension is driven through the centre of the mainshaft and this lifts the pressure plate with the three springs and cups. There is no adjuster in the centre of the plate. Adjustment is at the cable end where the cable arm clamps on to a screw worm, that drives the pushrod.
All the above might be completely irrelevant to you, but today, on a run, the clutch lever gradually came in towards the bars over about 10 miles leaving the cable slack. Obviously a problem somewhere - either the cable fraying and stretching, or the activating arm slipping on its worm, or the clutch falling off. I got some more lever life by winding out the gearbox top cable adjuster and rode home a further 10 miles maximising clutches changes - I just made it with the lever back to the bars again!
Taking the clutch apart this afternoon I found that the clutch centre attachment nut was a turn or two loose, so that explains all. I partly rebuilt the gearbox about 1,000 miles ago and fitted a new sleeve gear bearing. My notes say that I reattached that nut to 30ft/lbs, so now I have redone it to 50 ft/lbs.
What has me slightly concerned is that the mainshaft appears to have 0.035" end float. So the whole clutch is floating by this amount, which is probably not stressing the chain too much, but I would prefer it to be less play. The mainshaft rotates nicely and no up and down play, similarly the clutch chainwheel on its sleeve gear bearing.
Unfortunately, I made no note of whether that end float of 0.035" was there when I assembled it 1,000 miles ago. I am not going to take it apart but will just run it and see how it goes. Anyone out there have thoughts about gearbox mainshaft end float, and how tightly to affix the clutch centre on a laydown box?
mainshaft end float
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two nuts
Paul thank you for your thoughts. A lock nut is a potential solution, but since the nut in question can only be turned with a decent socket, goodness knows how you might secure a lock nut?
I ought to look up the recommended torque loading for a cycle nut on the mainshaft stub diameter, but we are talking about 70 year old components and the risk of overloading.
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Loctite it on. That stopped…
Loctite it on. That stopped all mine undoing themselves. (Both ES2's and a T150) And not too difficult to undo it again as long as you don't use the super strong stuff.
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yes, have had exactly the…
yes, have had exactly the same issues with my 1949 ES2 upright gearbox. For some reason the clutch centre nut decided to undo itself after years of use and at less than 6 miles from home after a 1500 mile round trip to do the Irish Rally. Not being sophisticated, I used a small amount of threadlock when refastening and have removed and replaced a couple of time since without further problems. As for the endfloat, I replaced the thrust washer, problem resolved. Great gearboxes when fettled, great bikes.
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The horizontal box
was a big improvement because the external link between positive stop and camplate sector was removed. Lots of wear in the link.... otherwise they are the same box.
When I took mine apart, it was in excellent condition, apart from the main bearing being worn. The bearing housing was so tight that I failed to get it in, and a machinist friend with a gas torch got it REALLY hot and popped it in. I didn't dare look.
I improved my horizontal box by building up the selector pawls in the positive stop mechanism, so there is much reduced free play before action.
The camplate in an AMC is a huge improvement. I hear that it is possible to machine out the gearbox housing and fit this camplate to the Norton-Burman box. The positive stop mechanism is also a big step forward
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Well two threads with…
Well two threads with exactly the same title....
Interesting to hear that exactly the same happened to you David. Fortunately I did make it home, but after removing the clutch I realised that my travel toolkit would not have removed or retightened that retaining nut had I been miles from home.
Yes I will loctite it (medium/soft) and I might try and find a locking washer. A heavy, sharp split washer seems very effective where there is constant low frequency vibration. They are the only things that will keep the 1/4" (5/16" ?) nuts on the rear sprocket of a Manx.
The end float can wait a bit longer :-)
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should be minimal. To reduce it you could fit a new bronze thrust washer or make a steel shim to go between the shaft and thrust washer. Reducing the end float will move the clutch to the right, and alter the chain line. It would be a good idea to check that the clutch remains in good alignment with the engine sprocket.
I think 50 lb/ft is the right figure. There are supposed to two nuts on the gearbox shaft to prevent it coming loose.