550 electronic ignition into a 650

OKC_Kent was asking about this is article in another forum.

Replacing Points with GPz Ignition

After years of those lousy, fouling points I came across a GPz550 at a junk yard and took its ignitor unit and the cam and sensors that are on the end of the crank (where the points would be on my '77 KZ650). They bolt right on and only cost me $20.00.
This was in 1994 and it's now March 2000 and it's been bulletproof. Before I would replace points every few months. No more fouling, and the fuel mileage is much better.
BY ZZJOECOOL

I was told that early 80's GPZ 550's were the ticket. I researched and found only two GPZ 550'S, the 1982 H1 and the 1983 H2 share the same igniter unit, part # 21119-1039. But the Pulsing Coil (same deal as a points plate) on a 1982 GPZ 550 H1 shares the same part number with the:
81 550 A2
82 550 A3
83 550 A4
80 550 C1
81 550 LTD
82 550 LTD
83 550 LTD
81 550 D1
83 550 SPECTRE
83 550 GPZ
83 550 LTD SHAFT

I put the stock 550 ignition from a 1981 KZ550A2 in a 1977 KZ650 and it was very easy except for one problem. The 550 ignition pickup plate is not slotted, so timing is preset and was way retarded on the 650 so slotting the plate was necessary in my case. Don't exactly know why the timing would not have been exactly the same between models, but it wasn't. I could have lived with it as it was, but the timing light showed ignition 1/2 way between the F and T mark on mine.

Ron, this is also true of 900/1000 electronic ignition swaps for points systems. The reason is that there are a variety of mechanical advance mechanisms. If you use the advance that came with the electronic ignition, it seems to work well enough but it only has timing marks for 1/4 on the KZ1000 electronic igntions and is not adjustable so the slotting mod makes sense...

It's probably that the reluctor's rotor also has an offset from the points cam. You can also adjust the timing by pulling off the iron slug from the rotor and pressing it back on in the right position.