Bill Vail (who posts on RCU occasionally) gave his MVVS 1.20 Twin to the late Jim Cline (Of Cline Fuel Systems) some years ago to sort out. He reports of success with a simple modification, and exchanging the supplied barrel rotor Walbro carb (which seems to be the main problem) to a butterfly Walbro carb suited for flowing suficient glow fuel.

Whilst not set up for all out performance, reliable running and idling was obtained, with Cylinder Head temps within 10 degrees F of each other. Carb Bill used (recommended by Jim) Walbro WA 46 G9.

Here are some pics