Stator Clearance

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Jun 12, 2007
I'm putting my chancase back together and can't get any clearance between the rotor and stator. I've had to replace the stator studs so is there a trick here to get it to realign? It's not a bent crank as the lack of clearacnce doesn't move as the engine rotates.

All help would be greatly appreciated.

Many thanks,
Check the fit of the inner chaincase. It should be flat against the crankcase and a straightedge along the front edge should show no gaps. The central mounting stud should have sufficient shims to preven the case from being warped. If you still have no play, remove the primary chain and check the crank for movement. If there is perceptible front to rear movement you have a problem that will require splitting the cases.

If you are satisfied everything is kosher with the crank, you can mark stud where it needs to be "tweaked" and remove them, keeping track of which hole each came out of. Thread two or three nuts on the engine side of the stud and mount it in a vice. Slip a length of pipe over the stud and gently bend the stud in the direction needed for clearance. Return it to the proper hole and remeasure. This should be done only as a last resort.
Hi, I assume you are talking about radial clearence between the rotor and the stator and the problem is that the rotor is not in the middle?

Here is what the experienced guys at the Norton Sweden Club recommended me to do (and successfully did).
1) The 3 mounting holes in the stator are approximately 8 mm dia. Increase the size to 9 mm by drilling. This will allow the stator to be adjusted in position with regards to the rotor.
2) Cut out a piece of a "cornflakes box", make it the size that would fit inside the stator (will act like a flexible paper shim in between the stator and rotor)
3) With the "paper shim" in place, push the stator over the rotor and the paper shim will give you an even 360 degrees clearance between the stator and rotor and the increased size (9 mm) stator mounting holes will allow the stator to move as needed.
4) Leave the paper shim in place. Now you can "seal" the extra clearance you have in the 9 mm stator mounting holes with "epoxi" or something else (I used selected pices of lockwire held in place by strong Loctite). There is different opinions on what is the best. Your call!
5) Fit the stator mounting washers (use the old thick type). Loctite and tighten the stator nuts per the workshop manual.
6) Remove the paper shim. Now you are done :D

You should get a better charging effect and even if the bike is left unused for long periods of time the rotor magnetism won't be negatively affected in the same way as when the rotor is much closer to the stator at one point.

An alternative to the cornflakes box is to cut two strips out of a beer can to use as a spacer between the stator and rotor. It's already pre-curved, measures about .010" when stacked on top of each other, plus it gives you an excuse to finish off a beer beforehand.
A milk jug is slippery plastic and so will slide out easer than all the rest. Not that I have anything against beer mind you. Mine is in bottles not cans.
Good idea with the beer can or milk jug. I have the same problem on my 850 - a rub at 3 o'clock. It does not appear that crankshaft runout is a factor.

I haven't tried to correct it yet because I'm a little squeamish with these procedures. Our club had a Tech Day last weekend and someone there suggested moving the stator into alignment by whacking it with a deadblow hammer at the high spot. I think I like the idea of drilling out the mounting holes better, but how do you drill through that laminated steel without having it all come apart? Is a drill press or mill required?

Ron, with your method of removing the studs to bend them, how do you get them screwed back in and tightened down, in the correct alignment? I don't quite follow that.

Maybe I'll just run it total loss for a while... :?

I used a sharp regular drill nothing special, just make sure to get it in the center of each mounting hole. The laminted steel did "open up" a little bit locally around the holes but installed and with the nuts torqued it was squeezed together again.

With the studs installed and tight, you mark the side of the stud where you need to tweak it. This will usually be toward the front of the motorcycle. You can continue the mark onto the aluminum boss on the inner chaincase to use as a reference. Remove the stud and thread the two or three nuts on it, locking them together so the stud does not turn. Place the stud and nuts in a vice, clamping on the locked nuts and with the mark facing you. Place a suitable length of small diameter steel plumbing pipe over the stud and bend it ever so slightly toward you.

When you screw the stud back into the case, the marks should line up after tightening, with the very slight bend in the stud toward the marks. I have known people to do this little maneuver while still screwed into the chaincase, but trying to bend a steel stud screwed into an aluminum boss makes me cringe.

Actually the idea of drilling the stator mounting holes slightly oversize and then packing them with epoxy is intriguing. But removing the rotor would seem to disturb this and require doing over again each time you needed to pull the stator, a job that I seem to do fairly frequently.

Since the clearance always seems to disappear at the rear of the rotor/stator what are the theories on why? Main bearing wear? It certainly isn't crank flex or the clearance would move with the rotation.

In any event, I do believe that a lot of riders run their primary chain too tight. Perhaps this accelerates any wear (at whatever location), that causes the rotor/stator clearance to disappear. My little trick is to adjust the primary and drive chains and start the bike. Allow the engine to warm enough to maintain a proper idle. If the rear wheel turns while on the center stand in neutral, the primary chain is too tight. Adjust (both chains!) and recheck. Again, always tighten the chain then loosen to proper adjustment.
Make sure that you have 0.010 clearance all the way around when you are finished 'cause I learned the hard (and expensive!) way what happens when you don't!!

Youngbutaclassic said:
I'm putting my chancase back together and can't get any clearance between the rotor and stator. I've had to replace the stator studs so is there a trick here to get it to realign? It's not a bent crank as the lack of clearacnce doesn't move as the engine rotates.

All help would be greatly appreciated.

Many thanks,
A lot of great information buried deep in the bowls of this forum. I am putting my 75 Commando back together after replacing the sparg clutch. I like the sound of the 9mm over sizing method. I was real close to using a different 9mm solution.
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