rotor-stator rub - ????

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joe czech

joe czech

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got into my primary case today for initial timing checks. first thing I find - rub marks on the rotor. it looks like I have slight rotor-stator interference or rub from about the 12:00-3:00 position. doesn't appears to be any means of adjustment. drawing a blank - seems I need to correct this issue before proceeding. any suggestions?
 
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joe czech said:
got into my primary case today for initial timing checks. first thing I find - rub marks on the rotor. it looks like I have slight rotor-stator interference or rub from about the 12:00-3:00 position. doesn't appears to be any means of adjustment. drawing a blank - seems I need to correct this issue before proceeding. any suggestions?
Click to expand...

Some people bend the studs. I drilled out the stator holes by 1/32 inch.
 
Try the simplest thing first .....

Loosen the stator nuts, insert a 0.005" shim or thickness gauge in three equally spaced places between the rotor and stator, tighten nuts, remove shims, then see if the clearance remains patent.

Slick
 
But be aware that catastrophic damage can occur if those parts rub. DAMHIK.
 
Try the shim & tighten fix before trying to bend studs ... I used cut up plastic milk carton last time for shim stock ...
 
If the simplest trick does not work, I would drill out the stator holes 0.005" over, then do the simplest trick again.

Bending the studs should not be necessary.

Another remedy is to take 0.005" to 0.010" off the stator poles. The wider gap resulting will reduce the stator's maximum output, but not enough to worry about, unless you are concerned about an amp or two.

Slick
 
Please never, ever bend the studs.

Either ream the holes in the stator or waist the studs so they are slimmer.

Bending the studs can damage your primary case - it’s just not necessary.


If you are seeing an uneven gap, this is a different issue to what we have been talking about recently in another thread where sometimes with brand new stator and rotor, there seems to be insufficient clearance between the two.

Your issue with less clearance between 12 o’clock and 3 o’clock is all about getting the stator centred about the rotor.
 
thanks for the replies. the stator was new - installed by the previous owner, although I tried to fit the original, and I seem to have the same fitment issue. there is absolutely no play between the studs and the locating holes in the stator. it's a tight very fit going over the studs. loosening the stud nuts buys me nothing. i'm thinking my only option is to open up the stator holes a bit, or "waist" the studs, or, maybe a combination of the two. definitely not a big fan of bending anything

second issue. I did a preliminary check on the timing. set TDC and rotated the engine to 30° BTDC. installed the outer primary case, and checked the timing indicator. the rotor mark was at 36°BTDC. I can't believe the thing's off by 6°, so a recheck is in order once the rotor/stator issue is corrected. anybody ever heard of the timing indicator being off by that amount?
 
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That situation was exactly the reason my friend sold me my commando 40 years ago. Misalignment burned up his stator windings. You can see how hot your stator has gotten by looking at the metal plate discoloration on the stator.

The cause is usually said to be an improperly shimmed primary case from the stand off to the cradle which makes the inner primary case flex and the bosses where the studs thread into are out of alignment as a result. 40 years ago, my fix was to drill out the stator holes slightly to have the ability to adjust the stator location. I've had no troubles since.
 
joe czech said:
thanks for the replies. the stator was new - installed by the previous owner, although I tried to fit the original, and I seem to have the same fitment issue. there is absolutely no play between the studs and the locating holes in the stator. it's a tight very fit going over the studs. loosening the stud nuts buys me nothing. i'm thinking my only option is to open up the stator holes a bit, or "waist" the studs, or, maybe a combination of the two. definitely not a big fan of bending anything

second issue. I did a preliminary check on the timing. set TDC and rotated the engine to 30° BTDC. installed the outer primary case, and checked the timing indicator. the rotor mark was at 36°BTDC. I can't believe the thing's off by 6°, so a recheck is in order once the rotor/stator issue is corrected. anybody ever heard of the timing indicator being off by that amount?
Click to expand...
Would not surprise me, esp. if your casing has been warped, leading to stator/rotor interfence. This is why I, and others, recommended you confirm that timing scale for correct reading.
So if you were setting 31deg BTDC on the incorrect scale as initial static timing, in reality you had 25 deg BTDC....which isn't too far away from the 28 BTDC recommended for points ignitions and some EI's. Don't think that would have been far enough out to prevent any engine starting.
 
BTW, while you are poking around in the primary, you might want to renew the crankseal. My '74 850 had that seal blow apart due to wet sumping startup pressures. Literally found it it two pieces. Can't expect much from a 45+ year old plastic seal.
 
update - played around with the stator mounting - here's where i'm at (the best I could measure) -- at the 2:00 position, I have about .003" air gap clearance, at the 8:00 position, about .017". in a perfect world, if centered, that puts me at .010 average which I understand is the high end of the .008-.010" factory spec. BTW, the new stator has two markings "wassell" and "16A". i'm guessing it a 200W replacement anyway, I'll play around with the stator mounting to see if I can get things centered up a bit more. at least the stator doesn't appear interfering with the rotor. also, measured the three spacers - two came in at .498 and one at .495. thanks for the replies....
 
Whatever you choose to do Don't bend those studs. A way back I tapped with a hammer to bend them a tad and the inner primary casting snapped off. Fun. Had to remove the primary and have it aluminum welded. Then a buddy said you should remove the studs and affix them to one of the "Z" plates to bend , same thread size and more solid. This worked but never again O.M.G.
 
update - waist cut the three studs approximately .016. I used a .010 polystyrene shim, centered the stator and torqued everything down. all is good. one (problem) down, a couple more to go.

thanks for all the help and suggestions. BTW, all you good folks have a Merry Christmas, Happy Holidays, and have a Happy New Year - enjoy the season! :)
 
maylar said:
Waiting for the video of that old girl running.
Click to expand...
hopefully soon. they say hindsight's 20/20, but it's probably a good thing the "old girl" didn't start. with the rotor-stator interference, things could have gotten real ugly inside that primary case.
 
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