New coils

[EvelKeevil]

I want to replace the coils on my '79 SF. I was wondering if it might be possible to simply use coils from a later bike - something like an FZS Fazer. Does anybody have any experience or anything to recommend? It would be helpful to find something that puts out a stronger spark but which doesn't need tricky engineering to fit!

[DEEBS11]

You can do a search for coils. The need to be the correct resistance with or without the ballast resistor.

[DEEBS11]

Didn't we just go through this with you?

https://xs11.club/forum/idle-talk-forum/xs11-xj11-discussion/888864-upgrading-coils

[EvelKeevil]

Didn't we just go through this with you?

https://xs11.club/forum/idle-talk-fo...pgrading-coils

Yes and no. Lots of very helpful and informative information for which I am grateful. What I'm now asking is whether it's possible to simply fit coils from another bike, plug and play. I also have a 1983 Honda CB1100F and have done this successfully on that bike, using coils from a CBR600. It required fabrication of a mounting bracket but has otherwise bolted on and is producing a far better spark than the original coils.

[DEEBS11]

Like I said, you need to use a meter & measure the resistance of the coil primary terminals and tell us what the number is. Should be around 3 ohms.

[jetmechmarty]

Google's AI says:

Ignition coils from Honda VF series motorcycles (such as the VF750, VF700, or VF1000) are commonly used as "plug and play" replacements for the Yamaha XS1100, particularly on 1981 models. These are typically 3-ohm coils, making them suitable for the stock ignition system.

Compatible Honda Coil Options

• Honda VF Series Coils: These are often cited as a direct fit, allowing users to cut the original Yamaha spark plug leads and solder them to the Honda coils.
• Aftermarket "Universal" 12V Coils: Many aftermarket 12V dual-wire ignition coils designed for Honda CB/Kawasaki KZ/Suzuki GS models with 3.0 to 3.8-ohm resistance also work.
• Dynatek DC1-1: While not a Honda coil, these 3-ohm aftermarket coils are highly recommended for the XS1100.
  YouTube +4

Installation Considerations

• Resistance: The 1980+ XS1100 models generally use 2.5-ohm or 3-ohm coils.
• Mounting: While they work electrically, you may need to modify the way the coil is mounted to the bike, as the bolt holes may not match perfectly.
• Wiring: The yellow (+) wire on the aftermarket coil connects to the Black/White (ignition/kill switch) wire, and the black (-) wire connects to the blue (points/condenser) wire.
• Ballast Resistor: For early models (1978-1979) that use a ballast resistor, you may need to bypass the resistor if using modern 3-ohm coils.
  YouTube +3

Always confirm the primary resistance (ohm) of the coils to avoid overtaxing the XS1100’s Transistorized Control Ignition (TCI) unit.

I bet all this came from this forum>

[DEEBS11]

If they turn out to be 3 ohm make sure you bypass the ballast resistor.

[EvelKeevil]

Thank you, much appreciated.

[jetmechmarty]

From XS650.com:

Sounds like you may have a bad coil. Many times when a coil goes bad, it acts up when hot but works fine when cold. A nice cheap replacement is a used Honda MP08 coil ......

about 3Ω, give or take.

These should fit the bill, and the budget.

[DiverRay]

On the resistor bypass, don NOT forget to tape it up! I ran one as pictured until the bike died 40 miles from home. It shorted to the frame even with the shrink tube on the connectors..