Yeah it'd work Dave but why spend all that money when a simple Yamaha trailbike ignition will work as well as anything. The DT or IT Yamaha external flywheel CDI ignition is exactly what you need, especially since you're only going to use the bike for dirt track. Ring around the wreckers and keep an eye on eBay, both Aussie and US. I've got a couple of PVLs and Lozzas exotic ignition but I'm using the DT ignition on both of my 360's as I want the extra flywheel on the big engine. I'll use PVL and "Lozzatronic" on my 250's. If you have trouble finding a DT CDI unit, you could revert to the external flywheel points setup as we did back in the day. It works just fine and you can get 'em for as close to free as you can get. Whatever you use.....you need the heavy external flywheel, not an internal rotor ignition like the original.
