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ChadS
11-25-2005 11:10:09
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Re: bringing my Cub soup-up thread to top in reply to R-cubed, 11-25-2005 10:15:02
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There just is not alot of snot in these little tractors! My 2 cents is this,,, Usually when more cfms need to go into the intake fromt he carb, you have to have a variable that spells it out, best variable is a vacuum test. Now, I dont know what the pressure reading would be, but maybe someone would be nice enough to put a guage on their cub and you put one on there, and compare the two readings. If you vacuum pressure is much higher than the engine you compared it to, then yes, a larger venturi might help you gain a little more power. If your carb can deliver plenty of fuel already, (if they have a main load adjustment) then yes you could stand to use a bigger air passage, the reason would be, if the vacuum pressure is so high, it will over power the carb and suck too much fuel into the intake,, a bigger carb will lessen the vacuum pressure and mix a larger amount of fuel with more air. Jet size compensation will keep it from having to run it with the choke on, but,, you could lose low end power with a too big of carb,, I dont see your improvemnt in size hurting your engine on your cub, Id say 3/4 diameter would be too big,,, On our cub lowboy, the problem with it is when I enguage the belly mower deck, it starts so quick that it will stall out the engine, unless I enguage the PTO slower,,, Dont matter if the engine is at an idle, or full throttle, it does it anyways,,,, Ive often wondered if its the carb, never tried to do anything with it,, but, it needs something,, just have not gotten around to do it yet. Ignition timing might help with the engines lugging ability, if it is already working the engine, then the governor and carb may be a bit more in tune with the engine laboring already,, in short,, its already posed, just ready to jump,,,,, Anything you can do, to improve responce time in how the engine operates, will help free up more power,,, but if all the important parts are just sitting there, (governor weights, distributor advance, carb jetting and venturi size) it will not work together efficently end result, less power. With out a dyno, its all hit and miss, test and test, just like your doing now. Just my opinion,, ChadS
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