To 3/4 throttle jet needle: the jet needle ( #2 in Will be, admitting more air to the jet block/nozzle screen leaning the mixture andĬonsequently a smaller cutaway will richen the mixture with its greater effect up to 1/4 The higher the number the larger the cutaway Substituted for one with a different cutaway. If the slow jet does not clean up this part of the circuit the slide can be Opened such as in a trailing throttle situation and the bike tends to load up and emits aĭeep tone when the throttle is returned to full open it is usually sign of a rich slow consequently, if the throttle is only partially Usually a sign of a lean mixture and the slow jet will need to be replaced with one larger
If the idle screw is properlyĪdjusted but the engine does not have good response when the throttle is wicked open it is Idle adjust screw (air/fuel screw) gives a good indication of a properly sized slow jet ( #6 in illus.).The slow jet calibrates the mixtureįrom both the idle bypass and idle orifice in the jet block. To 1/4 throttle slow jet and throttle valve cutaway: keeping in mind that the Replaced with one richer or leaner as required, consult your owners manual for the Need to adjust above or below this range then the slow jet will probably need to be Idle mixture screw usually has a range of one to two turns out from fully closed. In this case the screw meters fuel and opening this screw results in a richer mixture. Some carburetors have this screw located downstream of the throttle valve, Is located upstream of the throttle valve (slide) and meters air turning itĬounter-clockwise leans the mixture off idle. Such an adjustment will result in a sluggish responseĪdjustment screw: the carburetor pictured in the exploded view uses an airĪdjustment screw ( #5 in illus.) in that it
Keihin PJ series carbs in that the idle adjust knob ( #4 in If you do not desire any idle make sure you turn in theĪdjusting screw just enough so the engine will not idle. Throttle operation - (idle circuit) idle screw: depending on your type of ridingĪdjust the minimum idle speed to desired rpm making sure the engine is up to operating On FCR carbs the main jet, slow jet, jet needle, air adjustment, slow jet air adjustment and gas valve are different and located elsewhere. The guidelines are the same for both 2 and 4 stroke. This section features the PWK exploded views just to let you understand where the tuning components are located. Certain parameters may vary due to air pressure and temperature, altitude, umidity.īe carefoul when jetting, a bad jetting can produce huge engine failures.ĭon't do it yourself if you don't feel confident but let it to a professional mechanic.
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