I've been taking up the stretch in the new rear-drive chain on my 1951 ES 2 but guessing at what is the correct tension.
I have every Norton-related late 40s and 50s shop manual and book that exists...but nowhere does it specifically say how much play I should leave in the rear chain. My guess is that the adjustment might be the same as a rigid frame ? And this would differ from the later featherbed swing arm ?
I assume that since the rear wheel does not swing through the large arc of the swing arm that perhaps you set it a little tighter but then I worry that the old bones on my ES2 might not appreciate much tension on the gearbox end...
any advice would be appreciated
Grant MacNeill, Toronto
Good question. I'd have t…
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Hi Grant. Your question ca…
Hi Grant.Your question caught my attention because I had exactly the same thoughts a few days ago with my plunger ES2. It is the first time I have worked on a plunger frame and I just started its engine after it has sat idle for some 40 years.
A swinging arm will tend to keep the chain in constant tension, the error being greater the further the centre of rotation of the arm from the centre of the gearbox sprocket. The straight up and down movement of the plunger however will result in a greater extension of the chain as it moves away from a point a right angles to a line through the gearbox sprocket.
I always feel that the danger is to have them too tight as it will strain the gearbox and the chain will prematurely stretch. I have been guilty of leaving them too slack at times but I have never seen hooked sprockets nor used up chains. I always set swinging arm chains for 1 1/2" slack with the arm hanging down on the suspension units. I agree with Andy that this must be a 'gentle finger push test' as a good heave will add more movement.
I have also set my plunger chain to 1 1/2" reasoning that the amount of up and down movement is somewhat limited.
People often overtighten primary chains. There needs to be 3/4" slack because when an aluminium engine heats up it will force the frame apart and all that slack will have gone.
Norm
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Hi Grant, put the bike in…
Hi Grant, put the bike in gear on the centre stand and turn the back wheel to tension the top or bottom run of the chain, this will show the true 'slack' of the chain on the untensioned run. I give my 1950 plunger ES2 1+1/2 slack, i.e 3/4"up and 3/4" down play. I got this from a Norton article in an old Motorcycle Mechanics magazine.
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Thanks guys. i've been le…
Thanks guys. i've been leaving it pretty slack...well over a full inch of travel with gentle push of a fingertip. There is so little travel in the plungers that the chain could probably be tighter but I worry about stressing the gearbox sprocket end.
I feel better now reading your responses.
Thanks for the input Alan. Don't recall finding any mention of this adjustment in any of the period manuals I've read, Interesting how little this was discussed...I assume that in the rigid frame /plunger era, the writers of these manuals assumed everybody knew how much slack to leave in a chain. They did not account for guys like me who were born after the manuals were written. (grin)
Grant
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Good question. I'd have thought at least half inch play in the tightest spot. But don't fall into the trap of pulling on the chain as far as it goes, it needs to be the free slack rather than how far you can pull it if you really tried.
When I was doing the chain on my plunger ES2 a while back I adjusted it, then loaded the rack up and sat on it to compress the springs as much as possible, got someone to check it again and it hadn't changed much if at all.
Andy