Which type of coils for 77 gs550?

[johnhend]

So I measured 11.4 volts at my coils. I am thinking that this is pretty good so I'm looking for a new set of coils. Can't spend a lot. Found some Harley Davidson Super Coil 140403 coils on ebay for $40 with shipping. They came off of a gs 850 and they look brand new. Can I use these with my Dyna S ignition? Ebay also has some used oem coils, but I am shying away because they are just as old as mine.

 

[Nessism]

The Dyna S will work with coils that have between 3 - 5 ohms of primary resistance. The stock Suzuki coils fall in that range but I have no idea about those HD coils.

 

[mike_of_bbg]

Bandit coils are a popular choice for cheap, used, but much newer replacements.

 

[johnhend]

The Dyna S will work with coils that have between 3 - 5 ohms of primary resistance. The stock Suzuki coils fall in that range but I have no idea about those HD coils.

Where/how do I measure the resistance to the coils? Can I measure the resistance with the ground and 12v wires still attached to the coils?

Anybody know of a good source for aftermarket coils for less than $50?

 

[mike_of_bbg]

You should disconnect the plug and measure the coil primary leads. If yours are stock, they should be about 5 ohms. As Nessism mentioned, the Dyna S works with anything 3-5 ohms (actually they just say 3+, but you're not likely to find many >5 ohms anyway).

Personally if I were you I'd get the carbs rebuilt first and worry about the coils later. I think you're going to be OK there.

 

[johnhend]

The coils read 4.5 ohms.

 

[mike_of_bbg]

4.5 ohms primary is fine, within 10% of 5 ohms. You'll need to check the secondary (with and without plug caps) to fully check the coils.

The points bikes used a slightly higher rated primary because the extra resistance helps keep arc-ing down between the points. Now that your bike has a Dyna installed you can go down to 3 ohms if/when you feel like replacing the coils. No need to match what's there.