Coils interchange? '79 GS550

[psyguy]

Hi trusted forum

I'm asking this for a friend:

He's got a '79 GS550 that runs of the points.
Are the coils from a later model, '81 GS850 (that runs electronic ignition), going to work fine on his bike?

Cheers
Psy

[psyguy]

ANY thoughts?

[Buffalo Bill]

Coils are pretty much universal

I got coils from a '97 Bandit 1200 on my '81 550, not a problem. Because coils are mostly universal. The output is different, so you could compare the specified plug gap of the different bikes, and try them.
Bill

[koolaid_kid]

What you need to do is match the impedance of the current coils, or a little higher. For example, my 83 GS has 3 Ohm coils. I have read, but have no personal experience with, that the points models have lower impedance coils. If this is true, you could use the higher impedance coils with a slight voltage drop. This should be verified, but I believe it to be correct. Of course, for best performance you should use the correct points-specific coils.

[psyguy]

I have read, but have no personal experience with, that the points models have lower impedance coils. If this is true, you could use the higher impedance coils with a slight voltage drop.

thanks kid.

do you know what sort of voltage drop we're talking about? anything significant?

anyone know what the impendance is on the points system?

[koolaid_kid]

You can't calculate the voltage drop until you know the original impedance.

[hampshirehog]

They'll work. Not sure if they'll bolt straight on though - if I remember correctly some (all?) of the 850 coils were longer than the 550 ones.