Hello all, I pickup a new walbro WJ-84 carb on *bay with the intent of using it on a 75cc 3W side carb engine. The walbro has a venturi dia. of 17.5mm and is a good 3-4mm larger than the stock tillotson. This Tillotson also happens to be the exact model that is used on the 3W-50i. Would this walbro be too much for a 75cc? Also why does 3W use such a small carb on this engine? The walbro on my G-62 has a larger venturi (15mm).

Thanks, Mike

Hi,
Some of my thoughts on this are. I think the 3W 75 is a reed valve engine and the valve is controlled directly by the pressure in the crankcase. It opens earlier and closes earlier and has a longer duration as a result. With longer duration you don't need as big of a carb. Also the 75 is probally timed for lower rpm and high torque, thus small carb. On the other hand by their nature reed valves engines can usually handle larger carbs. This is because they react to engine demand, rather then fixed intake timing. Thats my 2cents. Try it an see. you own the carb, so why not.

Dave