RE: Saito 150S Always Backfires
Ive got the same motor, Ive never had a problem with it. I would change the saito plug to an O.S F plug, in my experiance saito builds one hell of a engine but their plugs are junk. My 125 a would kick back if it wasnt primed good enough. Have you put oil down the push rod tubes? could have a sticky lifter. Not to insult you but was the Pistion at Top Dead Center when u checked the valves, and are they set so the feeler gauge has a sight drag pulled out of the gap? If none of that helps, then try cleaning the carb out, I out of ideas. Good luck