It's definitely a single-fire mag (both plugs won't spark at the same time - no "wasted" spark")Kickstarter said:I've got this magneato and I'm not sure what it is for. I was told maybe a ARD Triumph mag?
That cover looks like an XR750 cover I have gathering dust (I've got the cover, not the $$$ mag). The extra height is for the distributor. It's got an automotive-style rotor that provides spark every 180 (or so) degrees per mag rotation.
Horizontal XR750 mags are pretty rare, which is the only thing causing me to second guess my guess. Regardless, I vote for horizontal (goes in what would be the generator hole on a Sportster or K) mount XR single-fire mag.
Here's a drawing of a dual fire, horizontal mount Fairbanks mag for a KR or XLR racer. I believe (someone please correct me if I'm talking out my ass) the single-fire mags only came on XR750s. The rest of the mag is common between the later KR, XLR, and XR. It's worth some cash if I'm right.