Bill;

Just like SUs, Mikunis are essentially also a constant-velocity/variable venturi design aren't they...so it seems to me that they would similarly like (lots of) choking during engine warm-up (don't they have a provision for this?), a richer winter setting, and pre-heated air when its cold...all the things that we know SUs like when its cold...so exactly why did you change? ...was there really that much perf to be gained in the summer? ...sounds to me, as Shannon has already stated, that you may need to rejet for the winter...and maybe an airbox, taking carb-air from the exhaust manifold (from a 140)...what a pain...not to rub it in, but I just use my good-old manual choke, and go 3 flats down on the jets November to March...it costs $0 and I can do it at a red light if necessary, without missing the next green!

Cheers