I am convertina a 40 cc Zenoah from a backpack blower. I've finished the prop adapter and the carb spacer plate. However before I drill and tap the spacer I need to decide on which of two carbs I have available. I have a Walbro HDA with a 14.2 mm venturi bore and a Zama C1Q-SK5 with a 11.9 mm bore. I am a little concerned that the HDA may a little too large for a 40 cc engine. Does anyone have any experience or advice. It would be appreciated.

Will Varnado

The bolt pattern should be the same...either will work..I once put a Walbro SDC80 on a G62, way big, ran the same..
If you believe the conventional wisdom that a larger carb makes the engine run better use the Walbro..Since the bolt patterns are the same you could test both..I tried 3 different carbs on a G26, from 3/8 to 1/2, they ran the same within 100 rpm..did the same test on a US 41 and a G62, same result...So much for conventional wisdom..

Thanks Ralph, I'll try the HDA first.

Will Varnado

Check the pulse hole in the carb, the HDA series has the hole off center from the mounting holes compared to most of the other carbs...[8D]

Hi Will,
Did you check for the direction of rotation on the motor? Many blower motors run clockwise. This is only of concern if you are going to use the magnito. Most 40cc engines use 11mm to 12mm carbs for saws and blowers etc.

Dave

Dave,

This one runs ccw, but I am going to use a CH Syncrospark unit that I already have. If this one works out well I have two more of them.

Will

Hi Will,
That sounds great. Maybe you could even build a twin. About 90" would still on one engine. Gas engines are more reliable then glow. I always lost my glow twins due to engine failure at wrong time.

Dave