Stator number 2 !!??

MikeG · Apr 25, 2017

Two years ago I had to replace an almost new Sparx 3 phase stator due to a broken wire and potting that cracked and melted. I replaced it with a brand new single phase Wassel rotor and stator. Pulled the cover off for a look see at the primary and an oil change and found the stator gone to hell again. Potting is cracking and melted in spots and it looks like the elements (pickups?) are delaminating. It also deposited melted goo on the rotor which I had to scrub off with a brass wire brush. What causes this aside from poor quality? My charging system consists of a podtronics unit and AGM battery hooked to the alternator and a multi color LED charge indicator. It always showed 13.2 volts charge above about 2000RPM. The only high draw component is the headlight, a 35W H4 headlight that does not get used that often. No evidence of the stator rubbing the rotor but the air gap narrows down to about .006 in at one point. I've since installed a used original one I had around and it seems to be working OK. Am I dealing with crappy repro parts ( the Sparx for sure) or something else??

Torontonian · Apr 25, 2017

Rotor to Stator clearance . You've got to get it even ALL the way around..

pete.v · Apr 25, 2017

Torontonian said:
Rotor to Stator clearance . You've got to get it even ALL the way around..

+1 "THIS IS CRITICAL"
I have it the past used a sanding drum on the inside of the stator to clean up high spots. I thought of take a skin cut off the rotor, but plan A worked out fine. Put .010 shims in at least 3 point and tighten Pull out the shims and check for clearance. Repeat and adjust as needed.

MikeG · Apr 25, 2017

OK then..any way to perhaps enlarge/elongate the hole in the stator to get it right? I'm thinking it might be better than carving up the inner face? I've got a Bridgeport and I'm not afraid to carve things up :mrgreen:

acadian · Apr 25, 2017

Make a sleeve to wrap around the rotor out of cardstock, test fit the stator, the sleeve should slide on and off the rotor with no snagging. If it does snag, locate the tight spot and gently bend the appropriate mounting stud/s until you can fit the sleeve on and off with no snagging.

Nortoniggy · Apr 25, 2017

It is possible that the shims behind the centre bolt that holds the outer primary case on aren't correct so that rotor to stator clearance is ok with cover off but putting cover on and tightening nut distorts the inner primary case and closes up the rotor clearance. Easy way to check is to find a spacer to put over the centre bolt to simulate the outer cover, fit the nut and tighten it. Check the rotor clearance in that condition.

Ian

htown16 · Apr 25, 2017

I've found the way to bend the stator stud is to slip a deep socket on a long extension over it. That way the bend occurs at the base of the stud and the long extension gives you some additional leverage.

Torontonian · Apr 25, 2017

That method can fracture off the inner cover stud aluminum mount. They are quite fragile. A better way is to remove the studs and screw into the footpeg "Z" plates and bend them gently with above socket tool to bend them (or one...) a tad. Peter Turner has a much better way but I was drunk at the rally campfire and forgot it. Anyway you look at it clearance must end up even all the way around. I use a piece of plastic milk carton as advised as a removable slip to provide the necessary shim before tightening down studs.

MikeG · Apr 25, 2017

htown16 said:
I've found the way to bend the stator stud is to slip a deep socket on a long extension over it. That way the bend occurs at the base of the stud and the long extension gives you some additional leverage.

I like this idea, but am a bit afraid of breaking the bosses on the inner case that the studs thread into. Worth a try though I guess.

MikeG · Apr 25, 2017

Torontonian said:
That method can fracture off the inner cover stud aluminum mount. A better way is to remove the studs and screw into the footpeg "Z" plates and tap them gently to bend a tad. Peter Turner has a much better way but I was drunk at the rally campfire and forgot it.

Cross posting! Good idea, but on second thought stud bending seems a bit tedious since they all need bending to get the stator back on. Still thinking of opening up the holes in the stator itself.

Torontonian · Apr 25, 2017

I think that was what Peter was discussing but we were over the edge and in danger of falling into the campfire.

MikeG · Apr 25, 2017

Torontonian said:
I think that was what Peter was discussing but we were over the edge and in danger of falling into the campfire.

having fallen in more than once myself I'll be careful then :lol:
Thanks

pete.v · Apr 25, 2017

Adding, the inner primary, being independent of the crackcase and crank end with rotor, needs to be square and perfectly perpendicular and not flex at the center pivot bolt.

grandpaul · Apr 26, 2017

You might also want to rotate the crank and check to see if it may be ever so slightly bent and the rotor isn't running true...

MikeG · Apr 26, 2017

pete.v said:
Adding, the inner primary, being independent of the crackcase and crank end with rotor, needs to be square and perfectly perpendicular and not flex at the center pivot bolt.

Well I took it apart this morning, gritted my teeth put a socket and extension over the studs and gave a gentle tug. They moved easily enough to get an even .012 clearance all the way round but you can definitely see the stud towers flexing. I'm thinking that just over tightening the outer cover nut might be enough to flex the inner cover to cause misalignment. I used to like the single nut retention method over the 14 allen screws on the primary cover of my A10...now I'm not so sure?

Torontonian · Apr 26, 2017

Fettling... always the fettling.

MikeG · Apr 27, 2017

Torontonian said:
Fettling... always the fettling.

The way of the universe...true mechanical happiness is always just a turn of the wrench away but forever out of reach!
A curious side note though. I've never had this trouble on any Triumph or alternator equipped Enfield I've owned over the years, and I don't think I ever did more than just make sure the rotor wasn't rubbing. Why is centering it so critical then? Not saying it's not, just wondering why it is.

Torontonian · Apr 27, 2017

Could be the alternating magnetic fields are most efficient if centered. Alien Zen forces from space ? Could be expansions from heat draw the rotor too close to the stator at the narrowest point of gap leading to meltdown. Theories. R.I.P. Robert M. Pirsig. :wink:

MikeG · Apr 27, 2017

Torontonian said:
R.I.P. Robert M. Pirsig. :wink:

Nater_Potater · Apr 27, 2017

MikeG said:
I'm thinking that just over tightening the outer cover nut might be enough to flex the inner cover to cause misalignment.

Easy to do. However, the inner cover "should" be properly supported at the center bolt. Take a look at http://www.oldbritts.com/1973_g10.html, paying attention to the #11 shim placed over the center hold-down stud. This/these should be stacked so that, when the three bolts at the crankcase are tightened, that the inner cover just kisses the stack of shims. That way, tightening the center bolt won't cause the inner cover to warp, potentially moving the stator. If the inner cover's been off before (likely), these shims are easy to overlook.

Nathan

Stator number 2 !!??

Similar threads