Primary cases

Gentlemen...I am new to this forum, I live in Seattle and have been involved with british bikes for decades. I currently work on all British bikes in the local area as the main shop of 35 years has closed. Occasionally I run into a problem that stumps me and I float the question to the world at large to see if anyone else has encountered the same problem. My current head scratcher involves spacing the clutch basket (Commando) outwards to line up with the engine sprocket. I find this particular bike requires approx. 1/4" of spacer....I am used to .030 or thereabouts. Everything else lines up, my only option is to put in all the spacing material. What gives??

FOR TRADE: I have a set of MK3 primary cases in VG condition. I will trade straight across for a set of earlier ones.

HOW TO ADJUST THE REAR WHEEL PERFECTLY: The rear axle and swing arm spindle MUST be parallel. Therefore, if the distance is the same on either side the rear wheel is in alignment. NOW..since the swing arm spindle is buried, I use the rear isolastic spindle. Quick, easy, and accurate. Go out and check your bike...I'll bet the wheel is out of alignment no matter how hard you tried.

My 1971 Fastback came from Seattle, it came with a sizable invoice from a shop there for work that was never done.
I did notice the person I got it off was selling parts on eBay for a shop that had shut down no doubt it was the same shop.

I have never encountered a clutch hub that was that huge amount outboard of the front sprocket

usually just one or two Norton thin shims is needed

are you sure you have the front sprocket fully tightened onto its taper all the way?

something seems wrong otherwise, a quarter inch.....

The shop was called John's British Cycle

Poke's: GONE
MSI: GONE
Dewey's: GONE
John's: GONE

<sigh>

Maybe the TS main shaft nut has backed off allowing the basket to stick out too far.

Yes, stop. Figure out WHY it's needing that much shim. Them correct that problem first. Bent engine cradle from a horrific wreck? Crank sprocket on wrong (damaged/improperly installed on key, etc)? Re-check every possible variable.

frame has been to the frame straightener and now checks out A-OK.
engine sprocket is on the crank, no nut but tight on its taper.
I have gone through the trans and it shifts beautifully
output sprocket lines up with the rear wheel
the spacer on the top trans mounting bolt is in place
the stepped washer and circlip are in place.

I just cut a 3.16" spacer on the lathe and now the two sprockets line up just right.
??????
I would really like to know why it needs such a large spacer

Steve Maney cases and crank

Any chance you have a Mk3 style crankshaft that has had a pre-Mk3 engine sprocket fitted? That seems really unlikely, but it would move the sprocket outboard a significant amount. I believe Steve did make some Mk3 dimension crankshafts in the past, so it's at least worth a thought.

Ken

I have contacted Steve about this but he had no answer. Right now the sprocket is very close to the case. To make things line up, the engine sprocket would have to shift 3/16" TO THE RIGHT and would be then rubbing the cases. This is a real mystery.

seattle##gs said:

.......engine sprocket is on the crank, no nut but tight on its taper........

Click to expand...

Did you cinch it up then take the nut off or tap it on with a hammer or something? You might get lucky if you torque it to specs. just what came to mind. But then you also said that the sprocket is already close to the inner primary case, hmmm?

1up3down said:

I have never encountered a clutch hub that was that huge amount outboard of the front sprocket

usually just one or two Norton thin shims is needed

are you sure you have the front sprocket fully tightened onto its taper all the way?

something seems wrong otherwise, a quarter inch.....

Click to expand...

You probably have a gearbox which has a dominator main shaft. The difference between a dominator and a commando main shaft is 1/4 inch in length. When I bought the TTI box, it put the clutch 1/4 Inch further out as I was previously using the pre-commando box and racing clutch with a dominator sprocket on the engine. I've now had a splined carrier made to fit floating Jawa speedway engine sprockets onto the Norton crankshaft taper. I'm still using good quality single row primary chain with the manx clutch.

This is interesting, I too had to turn up a thick spacer to get the clutch sprocket to line up with the engine sprocket on my MKIII I know the g/box has been apart in the past by the PO' s, I wonder what else I will find inside? I never considered that a Dommy mainshaft might have been fitted. Many thanks for the info
regards
pete

Does your shim stack include the 3/16 (or there about) spacer that has a channel cut in it to capture the snap-ring on the main shaft? One of those and few shims have always "done-the-trick" for my primary alignment.

B.

dobba99 said:

This is interesting, I too had to turn up a thick spacer to get the clutch sprocket to line up with the engine sprocket on my MKIII I know the g/box has been apart in the past by the PO' s, I wonder what else I will find inside? I never considered that a Dommy mainshaft might have been fitted. Many thanks for the info
regards
pete

Click to expand...

I only knew about the difference in the mainshafts because about 40 years ago I wanted to replace one in an AMC box, and the dealer mentioned the difference. It is due to the introduction of the diaphragm clutch. When I built the Seeley, I used the old style racing clutch and a single row engine sprocket. I had about 4 Norton sprockets and they all had different depth tapers, so the sprockets sat out at different levels on the crankshaft taper. For racing the single row chain is adequate, however you have to maintain it - I think it is much lighter. The Jawa type sprocket carrier is good. To change engine sprockets, I simply undo the nut on the crank and slide the sprocket off - no puller needed, no breaking the taper.

Can't be a Dommi mainshaft. You mentioned fitting the circlip and cupped washer behind the Commando clutch. The Commando mainshaft is the only one that has the circlip groove cut in it.

Ken

correct about the different main shafts...completely different clutch.
I made the spacer, everything lines up well and fits inside the cover. Who knows? I move on...

So where did your 1/4 inch difference come from - which clutch are you using ?