Sparx rotor and stator don't align?

Thanks for all the tips. I'm not gonna worry about it any more. If it's not charging enough, I'll save a few volts by removing the cappucino maker and putting it back on the Beemer....

Hi all - I am now installing a Sparx (3 phase) on my current commando rebuild. I have noted the same problem with the rotor being inside the stator by about 10mm. From what I read in this topic this looks like a common problem. I am wondering why Sparz instructions doesn't mention this as a possibility & advise either, not to worry about it, or sell the required spacer to correct.

I can have my machineist friend make me up a spacer to bring this into alignment... From your collective experiance, is this recomended?


Many Tks,

Biker-man - it doesn't appear to be necessary. "Misaligned" as it is, mine is still pumping out plenty of power. I think that alignment is just the way it is and is supposed to be. Wouldn't mess with it. FWIW.

Will someone please do the obvious?

dave M said:

Quite right Les, I was looking at a bare inner case and missing the obvious. One can always machine a little off these three spacers tp recess the stator a bit, although at a certain point I seem to remember that there are clearance issues.

Click to expand...

If anyone has a stock alternator set and a sparx set, will they measure the thickness dimensions of each to answer the question - why is the outside surface of the rotor/stator different when you mount stock versus sparx?

Hi Steve. I've just finished installing my unit which I assumed was an afternoon job. It took over a week of machining spacers and stuff at work and trying and re- trying stuff. I can't give you rotor thickness as it's already installed but the other stuff is- Lucas stator- 1.370", rotor- 1.387", Sparx stator 1.60". I don't recall the Sparx rotor being much different than the Lucas one. If you look at the inside surface of the Sparx stator you will notice that the exposed metal plates are offset towards the back about 1\8 of an inch which may allow for the rotor sitting back a bit. Important things I found are -
1. My rotor spacer has a 1\8" recess in it to clear the woodruff key. This gives it a small surface to bear against the back of the rotor. The Sparx rotor had less surface area than the Lucas and thus did not sit squarely on the spacer.
2. Be careful that the rotor sleeve nut does not bottom out its threads on the crankshaft before the rotor is tight. Mine did. I believe thats why the parts book lists shims for this. I ended up making a 1\8" overall wider spacer but this also meant I had to broach a keyway to clear the woodruff key.
3. I could not get a socket or wrench on the stator mounting nuts and had to make up 5\8" long nuts out of 1\2" hex bar.
4. I had to carve out a wee bit of epoxy on the back of the stator mounts as they where not clearing the aluminum bosses on the back of the primary case and the stator wasn't sitting flat.

I really think that brand new parts should have been easier to fit than this. The situation with the rotor sleeve nut also makes me wonder how many catastrophic rotor failures where really due to nuts bottoming out before tightening against the rotor.

In regards to my previous post, I found that due to increasing my rotor spacer by 1\8", when I tried to install my outer primary cover today the rotor interfered with the timing scale on the inside of the cover. This meant I had to pull everything apart again and re-think the spacer set up. It also means that for my bike anyway, the rotor would have to sit noticeably back in the stator.

Hi - I am having a 2mm spacer made up now as I was concerned with the retaining nut bottoming out & the fact the rotor was inset a bit. I hadn't considered the timing indicator though...

FYI - I did contact the sparx company who responded that they were not concerned that the rotor was inset, & it should be OK as is...

Update - I installed the sparx rotor today, The 2mm spacer worked fine, (rotor clears the timing indicator on the primary cover), there may be room for another .0030 shim, & definately room for a .0010 shim...

I believe the 2mm spacer was definately needed to ensure the rotor retaining nut didn't bottom out.