The shift interrupt should Not cut out the ignition if the cable is in
good working order AND adjusted correctly. The purpose of the interrupt
switch is to prevent damage to the drive from the throttle opening
before forward or reverse gear is engaged. A number of models did not
come supplied with interrupters at all. I would check the adjustment,
if incorrect, adjust to spec, if still sticking then check the lower
shif cable. You can sometimes see dried mineral deposits directly under
the engine end of the lower cable, indicating a leaky shift bellows and
probable damage to the cable, it only takes a few ounces of extra
resistance to cause a problem, but if you do have a shift interrupt
switch ,the engine will stall when shifting(as it should to prevent
damage.)..Also make sure your idle speed is correct...
markvictor