Stator clearance

slupdawg · Apr 14, 2009

I have another question for the wise ones on this forum.

While attempting to install a new alternator, I used a feeler gauge to check for a requisite .008" of clearance between the rotor and stator. There is interference from about 12:30 to 3:30. I assume it's the stator's position since I've turned the rotor and checked it out. Each time it's getting caught up in the same spot.

How does one go about fixing this problem?

79x100 · Apr 14, 2009

I would start off by loosening the stator fixings and seeing if it can be re-centered to give clearance all round. It may be possible to ease the mounting holes slightly.

slupdawg · Apr 14, 2009

I would start off by loosening the stator fixings and seeing if it can be re-centered to give clearance all round. It may be possible to ease the mounting holes slightly.

Thanks for the reply. Can you be more specific? are you meaning that I should enlarge the holes on the stator to center it?

79x100 · Apr 14, 2009

The old NOC Service notes suggest carefully filing the inner diameter of the stator but that seems a bit brutal to me.

'Easing' is a bit of a euphemism I'm afraid. I wouldn't go drastically enlarging all the holes but if a gentle caress with a round file were enough to centre it, perhaps by removing any burrs then I would give it a go.

Is it a Mk 111 that you have ? The NOC also make the point that the alternator carrier fixing there can be influenced at 3 o'clock or 9 o'clock by the chaincase centre fixing.

slupdawg · Apr 14, 2009

'Easing' is a bit of a euphemism I'm afraid. I wouldn't go drastically enlarging all the holes but if a gentle caress with a round file were enough to centre it, perhaps by removing any burrs then I would give it a go.

I might give that a try. I can't see how that would hurt anything.

This is a '73 roadster. My concern was that the end of the crankshaft stub was possibly bent, but I think I've ruled that out. The original Lucas alternator has a much sloppier fit clearance-wise than the aftermarket one.

grandpaul · Apr 14, 2009

I've found that a thorough cleaning with emory cloth (plumber's tape) of the inside diameter of the stator, and outer face of the rotor will result in a very nice amount of clearance.

slupdawg · Apr 14, 2009

OK, thanks for the advice guys, I'll give it a try. I was able to find a very fine round file with no taper at all to it. I'll try and use that very gently and see how it goes.

Cookie · Apr 14, 2009

I've also read an article by one expert who says to waist the stator studs as they are cheap and it makes no permanent change for rotor clearance.

Ron L · Apr 15, 2009

The factory manual states recommends "slight re-alignment of the studs".

What I have done successfully is to mark the side of the stud that needs realignment and then remove the studs from the case. Thread on a couple nuts and clamp them in a vise. Using the mark made as a guide and with a piece of tubing about 1 foot long slipped over the stud, very gently bend the stud slightly in the direction needed to give addtional clearance. Usually very little "adjustment" is needed. Make sure each stud goes back in the hole from which it came and recheck the clearance. Re-adjust as necessary.

Ron L

maylar · Apr 15, 2009

I resorted to drilling the stator holes a few thousandths over sized. Not my favorite kind of fix, but it seemed better than bending the studs.

I've had the unfortunate experience of catastrophic failure due to a rotor exploding, probably from poor clearance. It wasn't pretty.

Ron L · Apr 16, 2009

P11's and N15/G15's have the stator mounted in the outer cover making it nearly impossible to check clearance. Back in the old days I have seen a few smoking from the primary and a couple actually flame!

BillT · Apr 16, 2009

When I installed my stator, I cut a strip of plastic from a milk carton and slipped it around the rotor and before tightening the stator. Once I got the stator tightened, I pulled out the plastic and checked the clearance - no adjustment needed.

Cookie · Apr 16, 2009

Bill,

That sounds better than the old brass shim as you can get a milk carton about anywhere. That's another goood and inexpensive idea.

Thanks!

RoadScholar · Apr 16, 2009

Craftsmanship!!!

I went to install new tach and speedo cables the other night...

Somewhere in the process I decided to check to see if there was a "free spin" from each end with the other torqued...Guess what binding, binding, binding. If I had just *installed* the cables something would have worn out real fast.

So.

I played with the new cables and found out that the square wire cable ends were to big to plug properly into the tach/tackdrive or the speedo/speedo drive. A few minutes on the high speed grinder solved the length/size issues for both new cables.

Face it: you have an English "manufactured" item, the very defintion of everything is fitment, as in "built by craftsman".

My point is that everything you add or subtract from your English motorcycle needs to be "worked" back into the system...Like a craftsman.

I like it this way.

RS

tpeever · Apr 16, 2009

Cookie said:
Bill,

That sounds better than the old brass shim as you can get a milk carton about anywhere. That's another goood and inexpensive idea.

Thanks!

American beer can is also about the correct thickness. I used it to set the clearance on my Matchless G12 (also with the stator in the primary case) and it seemed to work great. Make sure you have enough clearance (0.008 minimum all the way 'round) as I also know firsthand what happens when you don't.

Cookie · Apr 16, 2009

A beer can, there's a method I can get behind.

Stator clearance

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