oslim Thanks. I bought several to use on variety of Homie and Ryobis. A search of muffler sites indicated that the exterior dimensions were very similar. I used two holes 1/2" .197si each x 2 = .395 si Exhaust port is .48 x .78" or .3744 si NO restriction. No pipes. Longer endplate screw & JB Weld to secure them and seal. Alum tube would make nice light compression tubes but none on hand

smallplanes I'm using a Wallbro 167-A 11.11 venturi. You need an I.D. difference on interior of carb. Take a close look near the throttle butterfly and notice a number of small holes , they are fuel jets and rely on a 'venturi effect'

Does anyone have a current Walbro # for same size but without the primer bulb cover on pump side? Picking is slim in an area that has little use for small gas engines.