I know some people have run diaphragm type carbs (Tillotson, Tecumeseh, etc.), but I haven't been able to find much info about them. As as I can tell, here are the deets:
-Cheap. Like, really cheap.
-No jets, so they're super easy to adjust.
-No float bowl, so you can mount them in whatever position you want.
-Readily available parts.
-Not gravity fed, so you can get creative with your mounting position
-You need to drill your case to accept a vacuum nipple.
-Possibly not quite as tunable? (only "low speed" and "hi speed" settings, as opposed to the multiple circuits on the nicer Mikunis and Dellortos)
-Apparently kinda weird throttle cable setup.
-No one seems to know much about them, so good luck getting help tuning it.
So who's used one? How do they compare to the usual Mikuni's, Dellortos, OKO's, etc. in terms of performance and ease of tuning?
My assumption would be, since they typically seem to be used on engines intended to run steady state (small aircraft, lawn mowers, weed whackers, stationary engines, etc.), their transient throttle response might not be fantastic. They also seem to be mostly used in a narrow RPM band, so I would guess they are difficult to tune for a wide range of engine speeds. That said, I know they're pretty popular among kart racing dudes because the lateral G's don't cause problems like they do in float carbs. So, what's the deal? If I could swap in one of these bad boys and never have to deal with jets again, I would be a happy man.