4H7 coils???

[RS Thornton]

Finally got my priorities right and I am back to playing with my toys. I picked up an '80 special earlier this year and just getting to it. There were electrical issues so the bike does not run (YET!), most of the issues appear to be the result of creative wiring by a prev owner. The last oddities (I hope!!!) is that the coils were changed to something else, the numbers on them are CM12-09 4H7, which may suggest an XJ750 as the donor. To make them work the bullet connectors in the wiring harness were replaced with a pig tail that matches the coil wires. Have any of you heard of this mod? Is there some benefit to it?

Because of all the creativity in the wiring I have pulled the old wire harness off and replaced it with an unmolested one so I am leaning towards putting the right coils back in unless there is some secret tuners reason for this set up.

Thanks,
Scott

[TopCatGr58]

Hey Scott,

I researched that coil #, and it turns out it's from the 82XJ1100 as well as the 81 series XS1100's, they have the 3.0 ohms, and do NOT require a ballast resistor. They possibly are also a bit stronger level of spark than the older 2H7 1.5 ohm model.

Unless you're trying to keep it purely stock...then you can either use them...if they meter out properly, OR you can replace them with new ones from MIkesXS.com, again get the 3 ohm kind, and just bypass the ballast resistor, it's not needed with the higher resistance coils!
T.C.

[RS Thornton]

TC,

Thanks for the details, that explains quite a bit. I thought that the 80 and 81 were the same based on the wiring diagrams I have, but looks like Team Yamaha slipped in some changes. I swapped out the wiring harness and had the coils with the harness so I swapped those out too. I will keep an eye on ebay for a 81 special wiring harness and likely go back to stock long term.

The bike was a gamble but it fired up this morning so I am hoping it can become another regular rider.

As usual thanks for the help, if you are still editing the FAQ on model differences you might want to make a note of the different coils.

Regards,
Scott