With a little trepidation I decided to add spark ignition to my Saito 90-TS. I had the ignition because I'd wrongly bought the wrong version for the Saito 182T previous conversion which was an odd fire engine and ultimately required two ignitions instead of the dual plug ignition meant for even fire boxer engines. The Saito 90 would sometimes drop fire in one of the cylinders so it seemed to make sense to put the unused ignition to use.
What I didn't know is if the single carb engine could be tuned on gas... if not, I'd run it spark glow. With ignition installed, it was run on glow first and performed well producing 8500 rpms with a MAS 13x8 prop. Idle would go down into the mud reliably at 12-1300. On gas, rpms dropped to 7850 with idle down to 2000 but the idle suffered the problem that one cylinder was too rich and would drop out. Below 2000, inertia couldn't carry rotation through the dead cylinder.
An 8 pitch prop was really too much pitch for the Cub the engine was fitted to so it was traded for a MAS 14x6 which was heavier and that did the trick, easily allowing rotational inertia to punch through the dead cylinder and idle between 17-1800 while yielding 7600 rpm at WOT.
It sounds great and should power the 1/6 Cub without problem, given that it was over powered on glow.
Attached is video of it being tested prior to fitting the ignition into the plane and changing the fuel tank to gas. The two engine stops are me hitting the throttle kill to illustrate the restart ease.