Touchy Feely

[Mosin]

Well, I got all my bits and pieces today including my brand new strobe, the illusive crankshaft spacer etc etc and took the afternoon off work with a view to getting everything back together and working. First I lined up the sprockets without the primary inner on using a straight edge accross the back of them. With the spacer in place it was very easy to get them perfectly lined up. I then refitted the primary inner, and the clutch, fitted my brand new primary drive chain adjusted the tension perfectly using the gearbox adjusters. everything seemed to be spinning just fine, so I fired her up and used my new strobe firing at my new SRM timing disk which was fastened to my new SRM cush drive nut to set the timing which I got spot on to 35 degrees BTDC fully advanced. I then took the bike up the road and she was running better than ever before and I was grinning like a cheshire cat by the time I got home. All that remained was to stick the primary case on and tidy up... a job well done...

Or so I thought.

Now the bloody primary outer case won't fit on. The new spacer means that the cush drive is now sitting further out towards the end of the crankshaft and it is fouling the inside of the dome on the primary case. So much so that there there is a half inch gap between the two halves of the primary case at the engine end.

I've spent about eight hours on the thing today and It's still not right. Bah. Can anyone suggest anything? At all? Please?

Cheers,

Simon

[chaterlea25]

Hi Simon,
A photo would be worth a thousand words??
The cush drive nut should be tightened fully and torqued 65ft lbs(??)
The nut should go on until the end of the crank shows through
The "missing" crank spacer should be the first piece fitted, this goes through the seal and buts up against the main bearing, then any shims then the cush inner splined sleeve, the nut should wind up clamping the splined sleeve in place solidly
I cant see how the case is half an inch away???? presumably you removed the timing disc????
HTH
John O R

[Mosin]

Hi John,

I'll try and get a photo, but basically all that I have on the main shaft are the spacer which is up against the main bearing. Next to this is the splined sleeve. Over these are the sprocket, the cush drive cam, the spring and then the nut which I did torque up to 65 ft/lbs. I have removed the timing disk, and even tried going back to the original cush drive nut, but all to no avail.

Simon

[Mosin]

Some pics.

Simon

[trevinoz]

Have you got the spacer between the inner chaincase and crankcase?
It is only about 1/8" thick.
As John says, the end of the crankshaft should be proud of the original nut, there is a hole for a split pin which must be exposed.
Trev.

[bsa-bill]

Looks like the cushdrive nut needs to go further on, you should not see any of the nuts thread within the end of the nut.
On mine there is about a quarter of an inch of the nut left before the end of the crank and my outercase fits on flush.
a small point that sometimes gets misunderstood is that the cushdrive is not a rattle clutch - it is not designed to fully slip if your gearbox locks up, it's role in life is to give a little when you drop the clutch thereby allowing a little feathering of the drive, to do this all that happens is the ramps move against each other a tad.
Try putting it together with the original cushdrive nut, if it goes on allright then check that the threads on the end of the crank are not damaged, I had to run a die up mine to get the SRM nut to screw on even though the original nut went on without any problem, maybe they use a tighter tap at SRM ( I think this might have been covered here once before)

All the best - Bill

[Mosin]

Have you got the spacer between the inner chaincase and crankcase?
It is only about 1/8" thick.
As John says, the end of the crankshaft should be proud of the original nut, there is a hole for a split pin which must be exposed.
Trev.

I don't have the spacer between the crankcase and the primary inner, but if it's only 1/8" then surely it wouldn't account for the measured half inch gap that I currently have. Would it?

[bsa-bill]

Spacer is more than 1/8, 1/4 at least IIRC.
Also the SRM nut covers the split pin hole (not needed they say) and due to the nut bit on the end the crank does not project through

[Mosin]

Looks like the cushdrive nut needs to go further on, you should not see any of the nuts thread within the end of the nut.
On mine there is about a quarter of an inch of the nut left before the end of the crank and my outercase fits on flush.
a small point that sometimes gets misunderstood is that the cushdrive is not a rattle clutch - it is not designed to fully slip if your gearbox locks up, it's role in life is to give a little when you drop the clutch thereby allowing a little feathering of the drive, to do this all that happens is the ramps move against each other a tad.
Try putting it together with the original cushdrive nut, if it goes on allright then check that the threads on the end of the crank are not damaged, I had to run a die up mine to get the SRM nut to screw on even though the original nut went on without any problem, maybe they use a tighter tap at SRM ( I think this might have been covered here once before)

All the best - Bill

Thanks for the thoughts Bill. I tried it with the original cush drive nut, but it made no difference at all. My SRM nut is tightened hard up against the end of the cush drive bearing sleeve (beneath the spring) and is torqued up correctly. The spring is pretty well compressed, although it does move as required, but there's no danger at all of it fully slipping under any eventuality.

[bsa-bill]

Hi trevinoz I misread your reply, my apologies  I thought you were talking about the other spacer, you have a good point there.
Mosin do you have the spacer that goes between the crankcase and the inner primary case, can't see it in your pics, it is a large spacer the same size as the hole in the inner case.
Also the spring is not compressed as much as mine is, somehow the nut needs to go on further, wonder if you've got wrong sprocket and cushdrive parts, I think there are different versions
Will take some pictures of mine tomorrow

[chaterlea25]

Simon,
It looks to me as if the nut is not fully home, ??
What thickness is the spacer you were sent?
The spacer should have a large internal radius cutaway this goes on the inside towards the radius on the crank and against the main bearing, if its inside out it will not go up against the bearing!!!!!
so the sleeve will not go far enough in, or the nut?????
If this is the case you will have to align the sprockets again???
HTH
John O R

[Mosin]

I am at work at the minute so am not in a position to be able to measure the spacer. However, I remember that it does have a cutaway as described on one side. I remember that this confused me a little because neither the bearing or the back of the sleeve has any sort of a raise on it for this to marry up with! This is weird.

Unfortunately I am now away for the weekend and won't be able to have a proper look at it until Sunday night when I think I will take off the primary chan and strip down the cush drive so I can measure the spacer. I will obviously take photos of everything so that I can feed back here for inspiration and advice!



Incidentally, This thread has now done a complete U-turn from being about ignition to mechanics and as such should probably be moved from the "Lucas & Electrical" board into the "Tech Topis" one if any moderators have the ability and feel the urge! Thanks!

Simon

[RichardL]

Simon,

First, let me say that I am not expert regarding plunger parts versus swingarm parts, particularly in the primary and, even less so, with regard to 4-spring clutches. Nevertheless, never one to resist sticking my neck out, I did a bit of research and came up with the pictures shown below (borrowed from www.basmotor.se, much thanks to them). It appears to me that the plunger splined sleeve is longer than that for the swingarm by about the exact dimension of your problem. Having said that, more experienced folks than I can jump in. It does not seem to me that thread at the bottom of the thread run would be so damaged as to resist 65 ft. lb. It would just give up and get more damaged. 

Anyway, whether this possibility is right or wrong. you are going to need that spacer between the crankcase and primary cover. With due respect to Bill, I recall (not near the bike right now) that it is much closer to 1/8 than 1/4. Nevertherss, you will need that 1/8-ish (and I'll enjoy eating that crow if I am wrong about the thickness.

Richard L.

[bsa-bill]

Hi Richard - I think you might of cracked it, it would explain mosins problem.
I did explain also in my last post that I had misunderstood trevinoz  post ( I was talking about the spacer that goes on the crankshaft  )

Tried to photo my parts this morning as the cover is not on yet but ran into the file to large thing and then ran out of time as I had to go out, but they would not have shown the difference in splined shafts.

Look forward to Mosins next mail

[chaterlea25]

Hi Simon,
I took some photos of the assembly from an engine I have on the bench,
As far as I'm concerned the spacer between the crankcase and inner primary varies from bike to bike and the thickness is governed by having to position the inner case happily between the gearbox sprocket and the primary chain, not forgetting the sliding plate/scroll on the back of the clutch centre!!!
more photos to follow
HTH
John O R