Rotor hole size

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maylar

maylar

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Anybody know what the rotor mounting hole size is supposed to be? I have a Sparx rotor that needs to be reamed to size.
 
maylar said:
What would you suggest for go/no-go?
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What does the shaft measure? I'd guess 0.752" is the correct rotor size as Burton states but will leave it up to others more qualified to answer.
 
You taking primary side off anyway , I would measure for myself .... just sayin’
 
few crank shafts laying here in the office-
With mic's: .7505, one only over 3/4,
most below, but closer to .750, down to .7475 smallest found
Agree .7502 sounds good
 
I was able to buy an almost new sparx rotor and stator off ebay for $35.00. When I received it and tried to put it on I had the same problem, the ID was too small. I suspect the seller had the same problem and waited too long to return it. I used a .750 straight reamer and it fits perfect now. I didn't use any go/no go gauge just a good reamer.
 
dynodave said:
few crank shafts laying here in the office-
With mic's: .7505, one only over 3/4,
most below, but closer to .750, down to .7475 smallest found
Agree .7502 sounds good
Click to expand...

Follow up - My crank measures .7505, rotor is at .7502. I could hammer it on but then it'd never come off again. Gonna ask a machinist friend to open it up a half thou.
 
Believe it or not the Sparx rotors were made to be an interference fit by design.

I used one on a Trumpet after reaming it.

I’d never buy one again nor use them on our beloved Nortons.
 
gtiller said:
Believe it or not the Sparx rotors were made to be an interference fit by design.

I used one on a Trumpet after reaming it.
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That's what I was told when I bought it. I sent it back to the vendor (Coventry Spares?) and they reamed it. It still won't fit my crank, needs a tad more.

I’d never buy one again nor use them on our beloved Nortons.
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Been using the stock Lucas rotor with the Sparx stator and regulator for about 15 years. Worked fine with a 9 AH battery, but the Li wants more volts. The magnets in the Sparx are definitely stronger than my 44 yr old Lucas.
 
Not a recommendation but...
I have checked 2 sparx rotors with my lab gauss meter and have seen a little more magnetism than new (recent) lucas rotors.
I was surprised...
 
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