We ran the Briggs (Not the imperial We, but a friend and I) yesterday for about three hours inverted. There were no ill effects.

The only issue that we had was with running the carb upside down we got poor performace, mount the carb (only the carb, not the engine) right side up and it performed great. I would really like to have a carb that I can adjust both the low and the high, the Brillelli (thanks Tim) carb was just too big to get it to run well.

The Briggs is 8.5 inches from the bottom to the top of the spark plug boot. From the center of the prop spacer to the top of spark plug boot is 6 1/4 inches. I am looking at the plans for my Sopwith Pup, the firewall at the cowl is 9 inches in diamater, so the engine, if mounted inverted would stick out the bottom of the cowl approximently 1 3/4 inches. I would need to cut a large hole in the bottom of the cowl to fit a Briggs. I dont know the specs on the honda, is it shorter? The sparkplug and boot are about 1 1/2 inches tall above the head so even though I would need to cut a large hole, the jug wouldnt show much from the side.

I used a turnbuckle to hook up the throttle, and I did cut the spring down so it only keeps tention on the barrel and slides easy.

The Fokker DVII is 21lbs with the Briggs and Stratton and the Pup is 12lbs with a Featherlite 25cc. Here are some pictures of the Briggs and Stratton engine, we made the custom exhaust so it would exit about the same place as the dummy engine header was.