Problems with new 12a start up lead to discovery of differences in dizzies??

I have dizzies with 2 different orientations of the flat spot on the shaft relative to the dimple on the gear.

On 2 of 3 of my dizzies the dimple and flat spot are in line. On the 3rd dizzy the flat spot is off by 90 degrees???

Could these be SA/FB dizzies, or could they have been mis assembled??

A dizzy swap using the same orentation has resulted in starting and idle around 1300, but the trailing timing made no sense and disabling it appears to improve idle.

Any clues about the orientation of the dimple and flat spot??

 

there are a couple of different advances, the 81-82 and 84-85's are different, slightly. however they stab the same.

since the gear is on with a roll pin it might* be possible to install the gear 180 off, which would be a little interesting.

really the only way its 90 degrees out is if something is broken, or the advance is stuck.

*i think you could, but the shaft is marked or something

 

If you look real close on both the gear sides you should fine a tiny o It seems to me that it can go on either way but if the gear is assembled with o up, put the roll pin in and I think you will find the o will line up with the pointer on dizzy base .. To me that would seem like the proper way weather it makes a difference or not .. The o wouldn't be there if there was no reason for it . I asked this question about 1.5 years ago but never did get an answer .. I have never checked but if the roll pin hole is off set it should make a difference JMO ,,

Also the early 1st. gen dizzy wires would need to be reversed coming out of the dizzy compared to the others or the base timing is wrong .. Bumpstart explained to me that the spark will get weaker as the revs increase and the built in advance works wrong ,,. All I know is if I don't reverse the dizzy pick up wires red to green and green to red on the leading on my project it runs like crap, reversed good .. I can't comment on the trailing because I don't use it but I would think it would be the same hope this help and doesn't confuse .. Gerald m

 

If the relationship is *exactly* 90 degrees, it shouldn't make a difference since the reluctor wheel ("Star Wheel") up top has four symmetrical peaks, 90 degrees apart.

SA and FB dizzys use reluctors with reversed curves from each other; if all your reluctors look exactly alike, all are either SA or FB dizzies. Additionally, no SA dizzy ever came from the factory with ignitors mounted to the sides - - another clue.

Could be as simple as someone previously diassembled the oddball dizzy's top half, and reassembled it to the bottom half-shaft incorrectly - - or as j9f says, it may just be busted or stuck. Time to disassemble it and look under the pickup bearing plate.

 

Had a good look at the odd ball dizzy and yes its messed up.

Thanks for the reply