Assembly of Primary Side

B-Stone · Apr 24, 2010

Hey guys,

Am slowly getting the bike back together however am currewntly held up at the primary. The PO had one spacing washer on the centre stud. When I put the chaincase on with one, it seems to leave a gap at the gearbox main shaft. If I removew the spacer, it seems to sit square.

Is it normal/possible to not require any spacers or am I missing something here.

Thanks

DogT · Apr 24, 2010

I think you first need to insure that the face of the drive sprocket is in line with the clutch basket face (so the chain is straight), and then you go on from there with the spacing of the primary inner cover. Others can check me out on this.

Dave
69S

Ron L · Apr 24, 2010

I think you first need to insure that the face of the drive sprocket is in line with the clutch basket face (so the chain is straight),

While the alignment of the chain is important, it really doesn't affect the chaincase alignment. The chaincase stud is mounted on the cradle so you are trying to mount the inner chaincase flush with the crankcase and shim the mounting stud so it will not put stress on those three bolts holding it to the crankcase.

I would take a good look at all the crankcase-to-cradle bolts. These can work loose and wear an oval hole in the aluminum crankcase. This will allow the engine to shift in the cradle and affect the alignment of the inner chaincase (among other issues). Many race engines have had these mountings sleeved and reamed to fit closer tolerances on the studs and bolts.

MexicoMike · Apr 24, 2010

Mine took a .009" shim to be perfectly aligned from the crankcase to the stud. This was after adding the 5/8" spacer between the tranny and cradle that the PO had left out. This spacer eliminated the rear drive sprocket's misalignment which wore a 1/8" deep groove in the inner primary case. Before discovering that the spacer was missing -thanks to a tip about checking for its' presence from this website - the cradle was warped (bent) inward under bolt torque almost 1/8 inch and there were several large washers needed to align the chaincase. So check that you have the spacer between the gearbox and left side cradle at the upper bolt for the gearbox before proceeding. (Part 34, Group 7)

B-Stone · Apr 24, 2010

Will check re the spacer you mention. 0.009" shim...that' s like three sheets of paper!

MexicoMike · Apr 24, 2010

Actually, it's also the thickness of a single-edged safety razor blade! I heated one red hot, let it air cool so I could work it and voila!

swooshdave · Apr 25, 2010

MexicoMike said:
Actually, it's also the thickness of a single-edged safety razor blade! I heated one red hot, let it air cool so I could work it and voila!

Why would you even bother for .009? How could you even tell? Won't the casecase expand and contract by that much just getting hot?

MexicoMike · Apr 25, 2010

I'm sure you are right that .009" wouldn't matter; call me anal (or is it amal?) Both, I guess.

swooshdave · Apr 25, 2010

MexicoMike said:
I'm sure you are right that .009" wouldn't matter; call me anal (or is it amal?) Both, I guess.

I think my other question is how did you measure it?

pete.v · Apr 25, 2010

Ron L said:
While the alignment of the chain is important, it really doesn't affect the chaincase alignment. The chaincase stud is mounted on the cradle so you are trying to mount the inner chaincase flush with the crankcase and shim the mounting stud so it will not put stress on those three bolts holding it to the crankcase.

If this is not done as Ron L states the inner case will warp from the stesses put on it from being miss aligned at the crankcase. The outer cover will not seat up proper to the inner and will leak. I would not be so concerned with the gap at the gearbox. The felt is there to take care of issues in that respect.

MexicoMike · Apr 25, 2010

With inner primary bolted to crankcase I was able to slide a .009" feeler gauge between the chaincase and the washer on the stud. I looked around for something of that thickness and found that the razor blade was the same.

pete.v · Apr 25, 2010

Give it a few extra thou for compression of the gasket and such.

batrider · Apr 25, 2010

As I remember Mexico Mike had some interference between the back of the inner primary case and the swingarn end cap and was trying to open that area up. A .009 gap pulled up on the center bolt would probably double or triple at the far right side, so he was able to get just enough clearance where needed.

Norton did make shims for this purpose so I guess it mattered to them.

Russ

swooshdave · Apr 25, 2010

batrider said:
As I remember Mexico Mike had some interference between the back of the inner primary case and the swingarn end cap and was trying to open that area up. A .009 gap pulled up on the center bolt would probably double or triple at the far right side, so he was able to get just enough clearance where needed.

Norton did make shims for this purpose so I guess it mattered to them.

Russ

Except their shim is .027 or if my math is correct, 3 times the thickness Mike needed. Do you need the gasket at the crankcase or would a good sealant work just as well? Something that doesn't harden?

pete.v · Apr 25, 2010

I was think about .009. That distance isn't really enough to warp a case to leak. The shims being 27 thou tells you the the fat oring around the case would more than compensate for .009 with no problem. I think you are good to go with .009, Mike.

MexicoMike · Apr 25, 2010

It's all together now (with the .oo9 shim) and has been running around Mexico City quite happily.

Just to be clear, there was ONE of the normal .027 washers needed plus the .009. If I gave the impression that ONLY the .009 was needed between the seating area of the stud and the chaincase, that was incorrect.

Yes, my alignment was way off by previous owner due to the warped cradle caused by the missing gearbox spacer which, in turn, caused the rear sprocket/chain to wear a groove in the inner chaincase. Because of the cradle warpage, there were several large washers between the inner case and the stud, which then caused the case to be slightly warped. Oddly. one would think that with MORE washers, there would have been greater clearance between the rear drive sprocket and the inner chaincase but the cradle warpage caused the Gearbox/sprocket/chain to angle toward the chaincase at the rear end of the case, enough to cause interference. These added spacers also cause the primary chain to lightly rub on the chaincase.

Now, with proper alignment of everything there is plenty of clearance for rear drive chain/sprocket and the primary chain.

swooshdave · Apr 25, 2010

MexicoMike said:
Now, with proper alignment of everything there is plenty of clearance for rear drive chain/sprocket and the primary chain.

And the picture of your success is where? :?

MexicoMike · Apr 25, 2010

Sadly, I didn't take any of the process. Only pic I have is of the inner chaincase where you can see the groove from the chain and the little circular wear point where the swing arm was hitting. Often I intend to take pics but in the heat of the disassembly/assembly moment (or hours) I just lose track of it. My Nikon D80 sat right there on the bench the whole time...

swooshdave · Apr 25, 2010

Did you use a gasket on the crankcase?

MexicoMike · Apr 25, 2010

Yes, I used the correct official Norton gasket, not the oreo cookie box gasket that I made/used previously. Oreo cardboard worked fine but to be able to use it I had to eat all the Oreos in the box. Oh well, the things we do to keep these Commandos going!

Assembly of Primary Side

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