Reply To: Stacy: R-Max Vs CSC & carb questions need answers

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Rodney Ebersole

Tom, All tillies metering holes are drilled threw the carbs body. Even the low and high side needle holes are drilled into the carbs body. The low side needle controlls the amount of fuel that enters under the low side soft plug, which is a plug that covers three different holes. The size and position of these three holes controll the amount of fuel that is available and mixed with changes in the air velocity seen flowing through the venturi. These holes can be seen looking down the carbs bore. Even removing the soft plug by an inexperianced person can result in a ruined carb with a wrong size hole in the wrong place of the carbs venturi.
Jet changeing of a tilly includes drilling of the carbs body in 7 possible areas for improvement or losses in controlling the fuel to air ratios through out a motors air velocity speeds. This is why with out any jet kits a tilly can be changed from the fuel requirements of gas to meth. That along with fine tuning of the high and low needle screws, makes the tilly quite appealing to on and off the track tuning. If all these holes were adjustable with out “machining” the carbs body, the tilly would cost more than a rotax slide carb, all it’s jetting kits, software and hardware.
If the loose term “jetting” is open in the rules, what would stop someone from elimating the fuel that has to go threw the venturi, replacing it with more air and introducing the fuel at the intake port? That would give me 7% more available air to flow through my resricted venturi size. I have a Tilly and intake that does this but it is set up for meth and drilling the drill pattern back to smaller sizes in the carbs body is quite tuff to do.