explanation please

seattle##gs · May 18, 2023

can anyone tell me why there is almost always too much clearance between stator and rotor about 10 o'clock to 6 o'clock and almost always too little clearance at 12 o'clock - 5 o'clock?
Theory #1...Norton drilled the holes slightly off in the primary cover and never corrected it. This could be either the big circle that indexes on the crankcase or the three studs for the stator.

Lineslinger · May 19, 2023

88 views and not one response.
Post some photos or a video of what your are describing. Some measurements of the fluctuation in spacing you note, stuff like that.
There are soooo many variables that can cause what you speak of.
My stator/rotor does not reflect the problems you are stating.

marshg246 · May 19, 2023

seattle##gs said:
can anyone tell me why there is almost always too much clearance between stator and rotor about 10 o'clock to 6 o'clock and almost always too little clearance at 12 o'clock - 5 o'clock?
Theory #1...Norton drilled the holes slightly off in the primary cover and never corrected it. This could be either the big circle that indexes on the crankcase or the three studs for the stator.

Yes, that is common. However, often the inner primary is improper shimmed. Also, the spacers are sometimes slightly different lengths. The bigger gap doesn't make a difference as long as the smallest gap is 0.008" or more.

seattle##gs · May 19, 2023

I experimented with shimming the stud for the primary case but no great results. I will try the three spacers.

KiwiShane · May 19, 2023

The inner primary cover is fastened by 3 bolts and is located by the inner/outer primary stud...those 4 things in my opinion can cause variations..(and bent stator location studs ?)..ive tried jiggling the inner cover around ...made alloy spacers to adjust the stator to get it central ...and machined 0. 005. off the rotor ...problem solved.

ILLF8ED · May 19, 2023

seattle##gs said:
can anyone tell me why there is almost always too much clearance between stator and rotor about 10 o'clock to 6 o'clock and almost always too little clearance at 12 o'clock - 5 o'clock?
Theory #1...Norton drilled the holes slightly off in the primary cover and never corrected it. This could be either the big circle that indexes on the crankcase or the three studs for the stator.

Somewhere over the decades I read, loosen the the nuts slight then gently tap the stator with a soft hammer on the opposite side of too little clearance. Tighten the nuts and recheck. Yes all the Commandos I have owned had this…’69, ‘70, 72, ‘73 750s. I don’t recall on the ‘74 850 JPN.

seattle##gs · May 19, 2023

The inner primary locates on the crank case...I cannot get any movement here. The holes for the three mounting bolts were drilled oversize so the case would drop on with no problems. Quite often the center stud is off center in its hole, indicating alignment problems. Expecting the old perhaps worn out machinery to hold those dimensions is asking a lot. Perhaps it was never set up right in the first place. So they made the same error over and over again, some a little worse than others. I notice the same problem in the same place over and over. I usually use a dremel with a sanding roll on the stator but the current one is a real problem.

KiwiShane · May 19, 2023

I also have taken a dremel to the stator ...in the end this sorted it out to get the required clearance i needed.

gortnipper · May 19, 2023

seattle##gs said:
The inner primary locates on the crank case...I cannot get any movement here. The holes for the three mounting bolts were drilled oversize so the case would drop on with no problems. Quite often the center stud is off center in its hole, indicating alignment problems. Expecting the old perhaps worn out machinery to hold those dimensions is asking a lot. Perhaps it was never set up right in the first place. So they made the same error over and over again, some a little worse than others. I notice the same problem in the same place over and over. I usually use a dremel with a sanding roll on the stator but the current one is a real problem.

I just used a deep drive impact socket on a T handle to tweak my double nutted studs a nudge.

ashman · May 20, 2023

No explaining needed the studs have to be adjusted to each stator/rotor from the factory they are done if over 50 years they probably have been changed, replaced so studs have to be readjusted for the stator/rotor to get it right and usually can be done with light taps but getting the right stud is the hardest to get right.

Bonzo · May 20, 2023

Norman White's book recommends machining a section of the studs down to 0.020in to allow a little stator 'wiggle room'.

marinatlas · May 20, 2023

make sure to machine them 20 thou and not 5mm (which are 200 thou) !

seattle##gs · May 20, 2023

That will be my job for today.

Bonzo · May 20, 2023

marinatlas said:
make sure to machine them 20 thou and not 5mm (which are 200 thou) !

Good spot

Bonzo · May 20, 2023

I've been doing this exact same thing today as, similar to the OP, my stator & rotor has little clearance at around 12 o'clock to 3 o'clock.

I took the precaution of buying 6 x new (060386) bolts in case one (or more) of the originals were bent. They weren't (of course they would have been if I hadn't have bought any

). I gave three of them to my youngest lad to machine for me at his work.

I may try ILLF8ED's tapping method, but weary of damaging the rear chain case stud bosses.

KiwiShane · May 20, 2023

Bonzo said:
I've been doing this exact same thing today as, similar to the OP, my stator & rotor has little clearance at around 12 o'clock to 3 o'clock.

I took the precaution of buying 6 x new (060386) bolts in case one (or more) of the originals were bent. They weren't (of course they would have been if I hadn't have bought any ). I gave three of them to my youngest lad to machine for me at his work.

I may try ILLF8ED's tapping method, but weary of damaging the rear chain case stud bosses.

By the sounds of things your lad on a lathe will be far more beneficial than a hammer...imo

Fast Eddie · May 20, 2023

Get him to turn a few thou off the rotor too.

I do. I always run a .020” gap these days on all my Lucas / Lucas replica equipped old nails.

No rubbing, no power issues. One thing crossed off of ’the things to worry about‘ list.

KiwiShane · May 21, 2023

Bonzo said:
I've been doing this exact same thing today as, similar to the OP, my stator & rotor has little clearance at around 12 o'clock to 3 o'clock.

I took the precaution of buying 6 x new (060386) bolts in case one (or more) of the originals were bent. They weren't (of course they would have been if I hadn't have bought any ). I gave three of them to my youngest lad to machine for me at his work.

I may try ILLF8ED's tapping method, but weary of damaging the rear chain case stud bosses.

I could be wrong but to me it looks like the stator maybe showing a sign of slight excess heat ...based on the colour of the resin at the top half of the stator compared to the bottom...?

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seattle##gs · May 21, 2023

I would prefer to machine the rotor and not the studs.

marshg246 · May 21, 2023

seattle##gs said:
I would prefer to machine the rotor and not the studs.

Before machining anything, do this simple test to ensure that the stator is not cocked in relation to the rotor. At the tightest point slowly push a feeler gauge straight in. If loose at first and then gets tight before going all the way in the stator is likely cocked. Another way is to find the feeler gauge that will go all the way in and see if a thicker one will go part way in. The spacers in my experience are NOT precision, often cause a cocked stator, and can often be moved around to eliminate the problem. If cocked and not caused by the spacers, most likely the inner primary is incorrectly installed and/or shimmed.

Fast Eddie's way certainly takes away the PITA but since I don't have access to a lathe, I try a little harder and have never had to turn, file, drill, or bend anything. I do lightly use a tapered hand reamer to slightly open the inside and outside of each whole, but that does not make the hole larger all the way through.

explanation please

seattle##gs

Lineslinger

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KiwiShane

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ILLF8ED

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gortnipper

ashman

Bonzo

marinatlas

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Fast Eddie

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Grant Tiller | Alternator Issues

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