750 to 550 coil swap

[Guest]

Hello happy bikers!
I suspect my 1981 gs550 has a faulty coil. Can I swap my coils over from my 1978 gs750 which I know are good to give it a test. The coils are a different size physically but will they be ok just to test and see if i need a new coil? (Are the voltages, resistances etc. the same).
Thanks, Davy.

[tom203]

Sure swap them. Have you tested this faulty coil? 3 to 5 ohms across primary connections and about 12000 ohms secondary plug wire to plug wire (remove plug caps and stick meter probes into plug wires). Compare readings to the known good coil.

[Davy]

Thanks for the reply, I am getting 3 to 5 ohms on the primary side of both coils. I am getting just over 12000 on the good coil and close to 16000 on the suspect coil on the secondary side.

[tom203]

Pretty close- should work. Are you getting a no spark condition on the two plugs from the suspect coil? If so, try swapping the coils around and see if no spark condition stays which would imply ignitor and/or connections. Take a look, here

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A17

[Davy]

Thanks, that link looks really useful. I got sidetracked cleaning the carbs, electrics might have to wait till next weekend.