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ES2 Plunger Primary drive sprocket alignment

Submitted by grant_macneill on Thu, 19/10/2017
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Hello ! the end is in sight on my ES2 overhaul !!

Today I'm installing my drive side engine sprocket, chain and clutch. When I lay a straight edge on the Engine drive sprocket, the surface is about 1/16 outboard of my clutch sprocket

I have the same version of drive sprocket that it was built with: Center-offset. An inside-offset would be too far inboard.

Perhaps this alignment was âas good as it getsâ in the 1950s ?

Maybe built-in play in the clutch basket sprocket, offers enough give that there is some âself levellingâ going on ?

Should I be worried or just proceed?

I could mill a little material out of the drive sprocket taper by handâ?and perhaps âsplit the differenceâ ; maybe get another 32nd closer to the crank case and improve the alignment but this is a lot of work.

I have about .030â between the inside edge of the sprocket body and the crank case; if I move it inwards then I must also remove material from the sprocket base or it will contact the crank case.

The old sprocket and clutch basket were only vaguely pointing at each other and never on the same plane for many many years.

Granted the primary drive in an ES2 was never machined to the tolerances of a high performance Commando...so perhaps Iâm over-thinking this ??

Does anybody have some advice for me ?

Regards

Grant

Submitted by george_phillips on Thu, 19/10/2017

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Hi Grant - the drive sprockets on the ES2 come in 3 types relating to the position of the sprocket on its "hub". The "in" version has a 5/32 lip between the sprocket teeth and the inner edge of the hub; the Mid position has a lip of 17/64 and the "out" position has a lip of 29/64". Can you measure yours and determine which it is? This would be a good starting point. The problem is that the difference between the above options is 17/64" Out to Mid and 3/16" Mid to In. None of these ties up with your offset. George

Submitted by george_phillips on Thu, 19/10/2017

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OOps! Just realised, Grant, that you are measuring from the clutch sprocket whilst my dimensions are purely on the drive sprocket itself. Nevertheless according to the figures given, changing the sprocket wont bring it into line with your clutch sprocket. George

Submitted by grant_macneill on Thu, 19/10/2017

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Previously George Phillips wrote:
OOps! Just realised, Grant, that you are measuring from the clutch sprocket whilst my dimensions are purely on the drive sprocket itself. Nevertheless according to the figures given, changing the sprocket wont bring it into line with your clutch sprocket. George
thanks GeorgeRGM sells the three offsets and I am considering ordering the "tooth position in" version which moves my offset 3mm inboard...a bit more than I need but closer to "centered" than I have now.But what I'm trying to determine is how much this matters. If I stick with the current off-set will this self-center itself in a few minutes of running or will it quickly ruin the chain and sprockets ?RegardsGrant

Submitted by george_phillips on Thu, 19/10/2017

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From earlier calcs that did the distance between the centres of the drive and clutch sprockets is around 450mm.Your 1/16" offset or 1.6 mm, equates to around 0.2deg so sounds as though it's hardly worth fretting over from a practical view-point. George

Submitted by richard_payne on Thu, 19/10/2017

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Bracebridge Street Nortons were well-made quality machines and I can't imagine that Edgar Franks in the design office nor the factory testers would have found misalignment on the primary drive acceptable.

There could be a a number of cumulative errors but it sounds as if it is the clutch positioning which is at fault and if the centre spider has not been replaced, I would suspect wear on the shoulder / abutment on the splines as this is what controls the lateral location.

It could be due to a mis-match of parts (who knows if some models differed) but if the clutch has been run loose, this will soon allow the shoulder to fret.

If it were my machine, I'd want to get it right and if the correct sprocket is being used on the crank, this has to be the datum point, and worked back from there.

Submitted by roy_cox on Thu, 19/10/2017

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Hi Grant

Whilst there are 3 different engine sprockets, there are two different clutch back plates depending on the gearbox type. Is yours correct?

Roy

Submitted by paul_knapp on Thu, 19/10/2017

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Hi Grant, I would think you are almost there, try loosening the engine and gear box bolts and give them a little bit of a wriggle around then check with your straight edge. I'm sure it wouldn't take much to get the sprockets in line. Also, end float on the gearbox main shaft would make a difference. Also, once the clutch is disengaged any sprocket alignment would change. Just find a happy medium, I recon.

Submitted by grant_macneill on Fri, 20/10/2017

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Previously richard_payne wrote:

Bracebridge Street Nortons were well-made quality machines and I can't imagine that Edgar Franks in the design office nor the factory testers would have found misalignment on the primary drive acceptable.

There could be a a number of cumulative errors but it sounds as if it is the clutch positioning which is at fault and if the centre spider has not been replaced, I would suspect wear on the shoulder / abutment on the splines as this is what controls the lateral location.

It could be due to a mis-match of parts (who knows if some models differed) but if the clutch has been run loose, this will soon allow the shoulder to fret.

If it were my machine, I'd want to get it right and if the correct sprocket is being used on the crank, this has to be the datum point, and worked back from there.

Hi Richard, I think you have nailed it. The spider is original and definitely worn. I am sure it is seating further in...closer to the gearbox than is would have the day it was assembled. I looked at replacing it and balked at the price. fabrication of a splined shim might do the trick but I'm looking at everything else first.

Thanks for the input

Grant

Submitted by grant_macneill on Fri, 20/10/2017

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Previously roy_cox wrote:

Hi Grant

Whilst there are 3 different engine sprockets, there are two different clutch back plates depending on the gearbox type. Is yours correct?

Roy

Hi Roy, yes the back plate and the thickness of the clutch basket cork would possibly shift the sprocket outboard which would be ideal.

My sense is that everything is as original but the spider spline wear is probably what has shifted this inboard a touch.

Thanks

Grant

Submitted by grant_macneill on Fri, 20/10/2017

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Previously Paul Knapp wrote:

Hi Grant, I would think you are almost there, try loosening the engine and gear box bolts and give them a little bit of a wriggle around then check with your straight edge. I'm sure it wouldn't take much to get the sprockets in line. Also, end float on the gearbox main shaft would make a difference. Also, once the clutch is disengaged any sprocket alignment would change. Just find a happy medium, I recon.

Paul

yes, I think you are right. I slackened everything off at the gearbox/engine plate bolts and managed to reduce the offset. and now if I take a line off the chamfered part of the sprocket about half way up the tooth, I get a good line to the clutch sprocket. Though off the flat body of the sprocket I'm still pointing very slightly outboard...so not perfect.

Allowing for end float on the crank and gearbox and clutch basket give when disengaged I'm thinking I'm OK.

an hour ago I reinstalled the sprocket with the drive chain and everything seems as it should be.

And the primary will be 100% oil tight !! (in a pig's eye) Grin

thanks for the help

Grant

 


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