Throttles and Throttle Kitsposted Jan 1, 2008
Tags: Reference, How To All Article Tags
At Motion Pro, we never refer to our throttles by fractional names (1/4-turn, 1/2-turn or other any other "turns"). How far a throttle fractionally turns is a function of the throttle's "rate" (how much cable inner wire the throttle's drum or cam reels in, versus how far in degrees the tube must be turned to reel it in) and the carbs/throttle bodies travel (how much cable inner wire must be reeled in to fully open the carb(s) or throttle body/bodies.
As an example, our fastest throttle, the Vortex, has a rate of 1.90 (the maximum number of degrees turned divided by the maximum travel in mm, 95º/50mm of wire travel). Since it has a maximum of 95º to turn, it will never be much more than a 1/4-turn throttle but in any application requiring less than 50mm of travel, it will be less than 1/4-turn to fully open. If only 25mm of travel is required, it will be about a 1/8-turn throttle. The opposite of the Vortex is our CR Pro; our slowest single pull throttle. It has a rate of 2.93, the result of a maximum of 170º turn and 58mm of travel. The rule of rates is simple; the smaller the value of the rate, the faster the throttle will open the carb.
Since we do not know the travel of your carb(s) or throttle body(ies), we will not quote a fractional turn. With careful measurement you can determine the approximate fractional turn required by a given carb and throttle by removing your existing throttle from your existing cable. Carefully measure the exposed inner wire (in millimeters) between the last fitting on the housing (the cap, elbow fitting, or threaded adjuster) and the wire end fitting (usually a ball or barrel). Do not include the wire end fitting in the measurement, only the exposed wire. Write down the measurement, it is your present "throttle free length". Now pull the inner wire until the carb is fully open against the stop and repeat the measurement. Subtract the throttle free length from the measurement you have just taken; this figure is the carb's "travel". Refer to the "rate" of the throttle you are considering. Multiply your carb's "travel" by the "rate" of the throttle. The result is the approximate number of degrees the throttle will turn to fully open the carb(s).
Notes: Do not consider any single-pull throttle (only one cable used) to replace any push / pull throttle (one pull cable and one return cable). WE WILL NOT build a custom cable to operate a push / pull carb with a single-pull throttle (including ATV thumb throttles). To fully open your carb, the throttle's maximum travel must be greater than or equal to the carb's travel or the carb will not fully open.
In most cases, your present cable will not work with a throttle of a different rate. Even if the rates are similar, differences in internal design usually require a different free length (the amount of cable inner wire required to reach from the end of the cables housing and housing end fittings to the connection point on the throttle tube's drum or cam). We calculate free length as a total figure, both the carb's required free length and the throttle's required free length are combined to determine the correct cable free length. This, in addition to the varied types of required housing end fittings, is the same reason you may require a special cable when you change your carb to a different size or type.
|Part Number||Throttle||Max Twist||Rate||Max Travel||Free Travel||Replacement Throttle Tube|
|TURBO (w/ Opt. Tube)||150º||2.00||75||902||01-0072|
|01-0060||Magura 314 mx||95º||1.90||50||70|
|Magura 314 enduro||105º||2.10||50||70|
1F/L measured thru TH-1245, for use with 01-0024 add 10mm.
2F/L measured from cap.
Rate = Twistº / mm Travel Max travel is measured in millimeters (mm)