Bob,
Thank you for joining this. I am not quite ready to purchase a Jett, but plan to in the future. Something you said in your thread was interesting, you mentioned the SJ-50 would get rich at mid throttle. I am ignorant about such things, but does that mean that my current cheap motor may not get rich at mid throttle if I change it's application and use it with smaller higher revving props?
David... just trying to help out a bit
I believe you may have mis-understood slightly here. With a bigger prop and lower rpm, the mid-range of a typical engine tends to need less fuel. A standard carb, designed for normal sport use, at a bit higher rpm, tends to deliver too much fuel in that transition stage with a big prop. That may be what you are seeing with your engine. What the H engine and 76 have are carbs tuned for the lower rpm ranges, to eliminate that problem. (pm if you want some of the technical reasons behind this).
With your current engine, you noted it does indeed tend to load up a bit in midrange (rich) and you are not comfortable with that. The first thing you can do is try a few different plugs. Try an OS-F plug in particular. Sometimes just a good ole K&B R/C idle bar plug can help. Also try turning in the idle mixture a tiny bit more. Let me know how you make out.
If you go back to normal sport or speed use of your engine, the carb will work just fine... will just take some re-adjusting on the low end mixture.
As Ernie here noted, the Webra carbs always seem to have good fuel flow. They tend to undersize the carb just a tiny bit on the production engines. They turn up nicely, idle well...and draw fuel. With a bigger carb, the engines are capable of very nice RPM output... but at the sacrafice of these qualities. (same as with the jett engines and a number of other engines).
Unfortunatly, sometimes the 'off-brands' tend to drive up their HP and RPM rating numbers by installing oversized carbs in the first place. Sure, they tune up and run well, and produce the power at higher rpms. But if you load them down, or reduce the exhaust backpressure (as you sometimes read about - engine problems with aftermarket mufflers) the inlet velocity drops to the point where its impossible to get a good needle setting on the engine - it just wont draw fuel. Some reading this may recall, that ASP included carb restrictors, just for this reason... as an example. Folks tend to resort to pumps to cure the problem (push fuel rather than suck fuel).
Anything I can do to help....drop me a PM.