stator

A while ago I replaced my primary belt ,in doing so you have to take off the stator and rotor , no problem I thought .fast forward to this weekend and out for its first run since and when I pulled over to stop it took about 20 kicks to get going again, so off I go and about 5 miles in it slowed and cut out altogether, nothing, dead as a dodo, i checked for fuel, spark and all seemed there, after 30 minutes and much kicking it fired up and got me home, when I took the primary off it was thick with belt debris so this was running out of line but that is a separate issue, I struggled to get the stator off but when I did I found scoring on the rotor so it must have been rubbing on the stator, would this cause my machine to cut out when hot ?
It has a Boyer power box and Trispark ignition and coil , can I file the rotor smooth and refit with the correct air gap ? what do you recon,,,,,,,

If the stator and rotor were working fine before they were removed surely you should be able to try a refit with a bit more care and attention?

As ‘standard’ now I get the rotor turned down to give 10 thou clearance (ie 20 thou undersize).

That gives ample space to insert a strip of cut up milk carton and create a spacer / jig when assembling to guarantee plenty of uniform clearance.

Works for me.

Yep, similar to Nigel, I use 10 thou brass shim-stock in 3 places to centralise the stator.
I have never had to turn down the rotor.
Never had rotor rubbing.
Cheers

robs ss said:

Yep, similar to Nigel, I use 10 thou brass shim-stock in 3 places to centralise the stator.
I have never had to turn down the rotor.
Never had rotor rubbing.
Cheers

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You’re either lucky, or using original Lucas parts, or perhaps someone already tuned them down ?

I am fairly convinced that modern reproduction parts run tighter clearances than they did originally. Probably because the manufacturers think they’re doing a good thing, and don’t fully understand what old Brit bikes really need?

Matt at CNW is now turning all the rotors with his 3-phase kits so as to eliminate this problem.
Mike

Thanks for the prompt replies all but when the motor is good and hot and the rotor has "expanded" and is making contact with the stator could this cause it to cut out ?

Yes, but... @Fast Eddie & @YING , I have used this method on my ES2 and 650ss.
Simple story - if 3 x 10 thou shims fit (equally spaced), chances are the rotor will spin without rubbing.
Not saying machining isn't required sometimes - but doing so will reduce charging current.
Cheers
Edit - thinking about it, machining should only be done to ensure the outer surface of the rotor is concentric to the crankshaft - ie, it doesn't wobble.

robs ss said:

Yes, but... @Fast Eddie & @YING , I have used this method on my ES2 and 650ss.
Simple story - if 3 x 10 thou shims fit (equally spaced), chances are the rotor will spin without rubbing.
Not saying machining isn't required sometimes - but doing so will reduce charging current.
Cheers
Edit - thinking about it, machining should only be done to ensure the outer surface of the rotor is concentric to the crankshaft - ie, it doesn't wobble.

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What I’m saying is, that with current offerings of rotor and stator I have been totally unable to get 10 thou shims twixt the two without machining.

YING said:

Matt at CNW is now turning all the rotors with his 3-phase kits so as to eliminate this problem.
Mike

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I have had 2 failures where the rotor made contact with the stator burning up and destroying the stators. First one lasted 263 miles, second time 100 miles. Both kits installed properly by experts with lots of experience. I'm going to install a new rotor machined .010" as directed by Matt which I'm convinced will eliminate this problem. First failure generated so much heat it caused the crank seal to fail bigly. I see a little oil this time but haven't taken it apart yet to see exactly where that oil is coming from. Crank seal or the 3 bolts securing the inner primary to the motor. Those bolts have been sealed on the first 3 phase installation with blue loctite, so I guess it's the crank seal again. If you do the 3 phase conversion, given the amount of people who have experienced this issue, absolutely have the rotor machined .010". Matt told me that doing that will increase the clearance anywhere from .012" to .015" and in different areas but the clearance will never be less than .010" and the output of the 3 phase will still be good.

colin davie said:

Thanks for the prompt replies all but when the motor is good and hot and the rotor has "expanded" and is making contact with the stator could this cause it to cut out ?

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Hey Colin, Yes.

When I bought my bike from a friend many years ago, the rotor gap was not correct. Whether it was just assembled carelessly or the primary chain was too tight and pulled the rotor into the stator is unknown, but the heat from the pair rubbing burned up the stator windings. My friend would charge the battery, go for a ride somewhere and then truck the bike back home when it wouldn't run later in the day. He did it for a few weekends and then sold me the bike since he didn't want to look for the problem.

If the rotor and stator rub enough, it cooks the windings in the stator which shorts it out so it does not charge. If you use a battery tender on your bike (like I do) you'll still be able to start the bike and run it for a while on just battery power until the battery drains down enough to where it won't continue running. If you let the bike rest, the battery might restore a bit of it's surface charge and you can run it again for a tiny bit longer until that charge is depleted also and then you are usually done as far as getting home on just battery charge once your stator is cooked and no longer charging.

colin davie said:

Thanks for the prompt replies all but when the motor is good and hot and the rotor has "expanded" and is making contact with the stator could this cause it to cut out ?

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Yes, correct this issue before pursuing another.

Thanks all
Colin