Quote:
Originally Posted by Danp
Gents,
Total length from carb opening to end of filter is 12". The 1-1/4" pipe itself is 8". Could it be too long, or am I needing to re-jet?
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Yes and yes! Before you start over remove the carb and note the jet sizes. Depending on the year of your motor and/or carb, they will have different size jets. Early years, pre '05's may have 114 to 118 jets. The EPA steps in with pollution restrictions so the solution was to lean out the carbs to meet requirements. you could find jet sizes at 108 to 111. With the velocity tube and UNI you will most likely need to go up into the low 20's on jets, approximately 122 range. 127 to 130 if you gut the muffler. exact size depends on your average elevation.
You are increasing air flow by as much as 40% You WILL run lean! Elevation plays a big part in how much jetting you need but regardless you got to re jet! or run the risk of burning up that motor. Those claiming no need to re jet either had early year carbs previously re jetted, got very lucky or didn't pay attention to the adverse effects
Your tube is too long. your loosing velocity. You have to take into account the carb throat length and coupler lengths. Remove the filter and measure the total length while installed on the motor. Slide a ruler inside the tube and gently bump against the carb slide. you should have 7'' +/- to the open end of the tube. Make sure that filter is oiled per instructions! failing to oil properly will greatly reduce efficiency and effect the air/fuel ratio