Primary chain case alignment

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Phliper00

Phliper00

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Sep 29, 2013
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Hey guys,
I did a small job on my engine head and I am putting every thing back together.

I am about to complete my primary case reassembling but if i look closer to the center stud, it seems that the inner case is not align properly by 1/16-1/8. I tried to fit the triplex chain and the alternator, but my rotor has the same problem with the stator.



How can I align the inner case? It sounds stupid, but can we « rotate » the engine by 1/16-1/8

regards,

phil
 
Last edited:
I am not sure where the 1/16” to 1/8” misalignment is relative to. Is it the case surface to the shoulder on the stud?

While the primary assembly is pretty “clumsy”, I have never had an issue with the rotor to stator perpendicularity unless the mounting studs were bent. By design, assuming the parts were manufactured correctly there should not be an issue – save for improper assembly.

The main datum for the assembly is the machined surface on the crankcase. It is machined (at least on my ’74 Roadster) so that it is perpendicular to the crankshaft bearings. The accompanying pilot diameter is tight but with the three ¼” bolts snugged-up the inner case is perpendicular to the crankcase.

In my estimation the next step is to lock down the inner case and shim the stud so that there is minimal preload on the case. The ductility of the aluminum casting material does not allow for a lot of “give” and improper shimming can result in the case cracking. The PO of my bike did not shim properly and the case had very fine hairline radial fractures.

While maybe not the best, my method for determining the proper shim-pack was to place some 3/8 washer on the central stud and then mock assemble the inner primary case on the crankcase with a new gasket. I tightened the three bolts moderately hand tight. Using a feeler gage I measured the gap between the trial shim pack and the central stud shoulder. On disassembly I measured the initial shim pack, added the measured gap and used that value for my final shim-pack measurement.

As the transmission essentially “floats” and is held square to the engine through the cradle it is not a significant factor in alignment. Using new stator studs the concentricity and gap of the rotor and stator were “good to go” on assembly.

Hope this helps.
 
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myron1950 said:
I am not sure where the 1/16” to 1/8” misalignment is relative to. Is it the case surface to the shoulder on the stud?

While the primary assembly is pretty “clumsy”, I have never had an issue with the rotor to stator perpendicularity unless the mounting studs were bent. By design, assuming the parts were manufactured correctly there should not be an issue – save for improper assembly.

The main datum for the assembly is the machined surface on the crankcase. It is machined (at least on my ’74 Roadster) so that it is perpendicular to the crankshaft bearings. The accompanying pilot diameter is tight but with the three ¼” bolts snugged-up the inner case is perpendicular to the crankcase.

In my estimation the next step is to lock down the inner case and shim the stud so that there is minimal preload on the case. The ductility of the aluminum casting material does not allow for a lot of “give” and improper shimming can result in the case cracking. The PO of my bike did not shim properly and the case had very fine hairline radial fractures.

While maybe not the best, my method for determining the proper shim-pack was to place some 3/8 washer on the central stud and then mock assemble the inner primary case on the crankcase with a new gasket. I tightened the three bolts moderately hand tight. Using a feeler gage I measured the gap between the trial shim pack and the central stud shoulder. On disassembly I measured the initial shim pack, added the measured gap and used that value for my final shim-pack measurement.

As the transmission essentially “floats” and is held square to the engine through the cradle it is not a significant factor in alignment. Using new stator studs the concentricity and gap of the rotor and stator were “good to go” on assembly.

Hope this helps.
Click to expand...
Here is the picture :

i know how to align the rotor/stator but the center stud seems to be at the right
 
Loosen the center stud from the engine/gearbox cradle. Install the inner primary. Align the stud in the center of the hole in the inner primary and tighten the cradle end. If this doesn't work, figure out why.
 
The inner cover is shifted to the left. Notice the issue with the rotor.
Loosen the 3 bolts at the engine and shift cover to the right.
 
As above. And check the spacer behind the inner cover, it looks like its possibly spaced out too much and is pushing the cover out in the direction that would cause (some of) your issue...
 
Fast Eddie said:
As above. And check the spacer behind the inner cover, it looks like its possibly spaced out too much and is pushing the cover out in the direction that would cause (some of) your issue...
Click to expand...
+1
 
myron1950 said:
I am not sure where the 1/16” to 1/8” misalignment is relative to. Is it the case surface to the shoulder on the stud?

While the primary assembly is pretty “clumsy”, I have never had an issue with the rotor to stator perpendicularity unless the mounting studs were bent. By design, assuming the parts were manufactured correctly there should not be an issue – save for improper assembly.

The main datum for the assembly is the machined surface on the crankcase. It is machined (at least on my ’74 Roadster) so that it is perpendicular to the crankshaft bearings. The accompanying pilot diameter is tight but with the three ¼” bolts snugged-up the inner case is perpendicular to the crankcase.

In my estimation the next step is to lock down the inner case and shim the stud so that there is minimal preload on the case. The ductility of the aluminum casting material does not allow for a lot of “give” and improper shimming can result in the case cracking. The PO of my bike did not shim properly and the case had very fine hairline radial fractures.

While maybe not the best, my method for determining the proper shim-pack was to place some 3/8 washer on the central stud and then mock assemble the inner primary case on the crankcase with a new gasket. I tightened the three bolts moderately hand tight. Using a feeler gage I measured the gap between the trial shim pack and the central stud shoulder. On disassembly I measured the initial shim pack, added the measured gap and used that value for my final shim-pack measurement.

As the transmission essentially “floats” and is held square to the engine through the cradle it is not a significant factor in alignment. Using new stator studs the concentricity and gap of the rotor and stator were “good to go” on assembly.

Hope this helps.
Click to expand...
All of the above
And throw that clutch tab washer away and use locktite instead
 
MichaelB said:
The inner cover is shifted to the left. Notice the issue with the rotor.
Loosen the 3 bolts at the engine and shift cover to the right.
Click to expand...

There is zero adjustment capability from the chaincase to engine. The crankcase has a lip that fits snugly into the back of the primary and those 3 bolt holes are not oversized for the bolts.
 
Unbolt the stud from the cradle and ensure it is straight, as in not bent. Spin it in a drill press, or roll it on a flat surface. If it is bent, straighten it.
 
maylar said:
There is zero adjustment capability from the chaincase to engine. The crankcase has a lip that fits snugly into the back of the primary and those 3 bolt holes are not oversized for the bolts.
Click to expand...

I understand what your saying, there is some movement.
Had the same issue on my 72, after careful positioning and shimming, it aligned correctly, including the rotor.
Sounds like he only took the top end and primary apart.
If that's the case, it should line up again.
The positioning of the rotor suggests the inner cover is not positioned correctly on the engine.
 
MichaelB said:
I understand what your saying, there is some movement.
Had the same issue on my 72, after careful positioning and shimming, it aligned correctly, including the rotor.
Sounds like he only took the top end and primary apart.
If that's the case, it should line up again.
The positioning of the rotor suggests the inner cover is not positioned correctly on the engine.
Click to expand...

this is what I am about to test. Thanks!
 
Everything affects everything.
Check this also.

Fast Eddie said:
As above. And check the spacer behind the inner cover, it looks like its possibly spaced out too much and is pushing the cover out in the direction that would cause (some of) your issue...
Click to expand...


Edit, I wound up tearing mine down. Once confirmed the center stud was straight, I worked the cover till the stud was centered, then shimmed accordingly.
Installed new stator studs, the rotor and stator were within tolerance.
 
Stating the obvious. When you fit the inner primary did you loosen the gearbox primary chain adjustment so that there is a lot of chain slack? The inner primary won’t seat properly to the gearbox if you don’t do this.
 
illf8ed said:
Stating the obvious. When you fit the inner primary did you loosen the gearbox primary chain adjustment so that there is a lot of chain slack? The inner primary won’t seat properly to the gearbox if you don’t do this.
Click to expand...

so I tried most of your ideas and I worked great for the case alignment! Loosen up the center stud was exactlY what I had to do.

so I now have to align my stator. I tried to put some shims behind it, no luck. I tried to bend the studs, but I am too scared not to be able to put it right again.

what are your thoughts? Thanks,
 
Phliper00 said:
so I tried most of your ideas and I worked great for the case alignment! Loosen up the center stud was exactlY what I had to do.

so I now have to align my stator. I tried to put some shims behind it, no luck. I tried to bend the studs, but I am too scared not to be able to put it right again.

what are your thoughts? Thanks,
Click to expand...
I used a box end wrench to tweak mine. Double nut the stud, should come out fine.
 
Phliper00 said:
so I tried most of your ideas and I worked great for the case alignment! Loosen up the center stud was exactlY what I had to do.

so I now have to align my stator. I tried to put some shims behind it, no luck. I tried to bend the studs, but I am too scared not to be able to put it right again.

what are your thoughts? Thanks,
Click to expand...
What are you aligning? The rotor likely will not be flush wth the stator, that’s normal. You should make sure there is .010 clearance between the two all the way around inside the stator. If there is a tight spot I tap on the stator gently. Check again after tightening everything.
 
I don’t like bending the studs, I really struggle how that can be accurate to a thou or two when using a BFH (Big F***ing Hammer)...! It also makes it a nightmare to remove the stair from the studs in future.

I prefer opening out the 3 mounting holes, if necessary (haven’t had to do it on my Commando though), then using some packing material to ensure perfect alignment as the mounting nuts are tightened.

It looks like you have a new stator there? My new stator was under sized, it would have been IMPOSSIBLE to get even the stock 10 thou clearance. I had the stator and rotor properly measured and the rotor turned down to suit. I actually doubled the clearance to 20 thou (40 thou under sized) and it works perfectly. Even with a carefully set 10 thou clearance I still had the rotor rubbing the stator (the bike gets revved hard), hence why I increased it.
 
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