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ChadS
11-06-2005 08:09:38
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Re: Hey Chad S Carb Question? in reply to MagMan, 11-06-2005 04:25:26
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Jon, What ever came stock on a M would be a great carb for your set up, due to the cubic inch, I think you could get away with the H carb and run just fine for general farm work, and the occasional play time on the track. Once you get the engine broke in, run a compression test. I would guess that it will be in the 150-160 psi range, so you may have to rejet the main load jet a few sizes larger to compensate for your displacement increase, and the compression increase from the head work you had done. If you have a gasoline carb, and not a distillant carb, you will not have to jet it up so much, due to the jets being larger in the gas carbs. Most hardware stores carry numbered drill bits,,, remove the carb bowl, and the metering stem from the bowl, and take the bowl with you to the store, match up the main jet size to the drill bit that fits best, then purchase 5 numbers higher larger drill bit, example, if the jet is a 50, you would purchase a 55 bit. Now, this bit will be your new jet size, what you would do is carefully drill out the main jet to the size of the bit. Be careful when doing this procedure, because you could accidently drill through the casting of the carb where the metering stem sits in. Now, once you have the main jet drilled, reassemble the carb bowl, and try it out. At full throttle, back outthe main load screw and see if you can make the engine run rich, or smoke from too much fuel. If you can make it smoke, Leave it alone and go for it. If you cannot, remove the carb bowl, and the metering stem. This time, you will use your drill bit to drill out the bottom 2 holes in the metering stem. The metering stem, is the long brass stem that sits in the middle of the venturi by the way,,, What this will do is allow more fuel to enter the lower end of the metering stem, filling the capacity of the metering stem quicker, and more fuel allowed to enter the stem from the main jet. It will get fuel to it after that for sure!! This modification will help aid cold starting, you will not have to choke it so hard to start, and we all know how cold blooded the H can be!! Once the carb jetting has been done, you will need to focus on your spark plugs for a short time,,, your looking for color on the plugs when the engine is under a load. if your carb is delivering enough fuel, the spark plugs will be a cocoa brown in color. You back out the main jet screw out for more fuel, in for less,,,,, Now for HP outputs between the small carb and the big carb,,, probably about 3 hp difference in the 2, but I would say for fuel economy, use the H carb. Hope this helps,,, any questions let me know. Good Luck! ChadS
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