i have found that it is better not to concentrate on the carb for increased fuel economy as it does sacrifice power....there are other methods of achiving better gas mileage without a high mileage ccarb...i have a carter YFA on my 250....easy to tune and rebuild....if u dont mind building a few things then nu can increase gas mileage without losing power by building a PCV gas condensator...this is a jar inbetween the PCV valve and the intake where the oil and crap that normally goes straight into your engine will be cracked and turned into fuel...all the other junk will stay in the jar and not go into the engine....this results in better mileage since more fuel and less crap is entering the engine...typical mileage increases for these jars is 25% better but there are ones that get 40% better mileage...the one i build gives me more than 40% im sure of cause i went 200km per 1/4 tank with it and about 80km without it...also depending how the engine is tuned will effect your gas mileage...same with the vac advance..u need vac advance....some carbs dont have enough vacuum to utilise the vac advance so then it should be hooked up to the intake manifold...take a look at page 3 of my website for more info on the pcv jar....
www.geocities.com/davevandrunen/ind3.html
