The 1977 Polaris SnoPro Engines for Jerry Bunke, Brad Hulings and Steve Thorsen had a little secret: Each was using a very unique ignition that was not used on any other machine.
They tried it on some 340s, but the vibration proved to be too much… but on the 250s, it really made the engine come alive.
I’d been trying to figure them out for some time and have been very fortunate to have met and gotten to be friends with one Boyd Burke, who today owns Jerry Bunke’s 1977 250 that is in remarkably original shape.
AJ Emerick was also a huge help, by sharing photos of his 1977 340 Jim Bernat engine, that had a complete version of this unique set of parts. Ken Simenou was extremely helpful when he started asking questions about this oddball setup.
Finally, Troy Pierce helped to put it all together.
So how to tell if you got one of these:
1. The CDI Box is unique. It had three plugs coming out of it: One white plug that goes to the stator, and two black, two-pronged connectors that go to the dual coil setup.
2. Yep, it uses not one, but TWO coils.
3. The magnets are on the outside of the flywheel, where on any other Polaris, they are in the inside.
I am in search of one of these CDI Boxes so if you have one that looks like this, please let me know!
It’s a rather small, thin flywheel, but in both these photos you can see the extrenal magnets.
Steve Thorsen’s 250cc IFS shows the dual coil setup.
And THANK YOU to Boyd Burke for taking the time to fully diagram the whole thing!
