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Dirt Bike Brands - Other
Pumper carb on KLX 300?
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[QUOTE="DualSportr, post: 140855, member: 19592"] A pumper carb, if set up correctly, will give you better low end throttle response and more top end. A four stroke really hates to deal with lots of fuel at low rpms. The engine only uses 1 batch of fuel for every 4 strokes. Basically, with a regular, butterfly or CV style carburetor (although the CV & butterfly to a lesser extent than the regular carb) the drill goes like this. Think of the engine like a pump. Now, the pump is being used to deliver fuel to itself. You open the throttle, which lifts the slide, allowing air to enter the carb - this acuates the pump. Fuel is drawn through the circuits, is mixed with the air and thrown into the head, which delivers it to the cylinder at the right time. Okay, this process is working really well at high rpm, the fuel and air mix, and whammo! they're channelled quickly through the head, then dumped into the cylinder and ignited. Now, imagine what's happening at lower rpm's. The "pump" is moving slower, you open up the throttle, the slide lifts, and the pump tries vainly to suck in the fuel. The fuel and air mix, and dribble into the head, where they sit and wait for the intake cycle. At low rpm, this takes forever, and the fuel gets tired of waiting. It falls out of the air - so it's no longer atomized - then the valve opens and the fuel and air dribble into the cylinder. Not a great situation to create that smooth hit of power you asked for when you twisted the throttle! The CV Carb (like what you have on your KLX) works a little better, because it doesn't use the throttle to control the slide - the throttle position is just a suggestion to the carb - the engine's pumping action is what lifts the slide. So in theory, the carb only delivers as much fuel as the engine can handle. Unfortunately, this can also create some weird carburetion when you let off on the throttle after an extended high-rpm romp (the bike won't slow down, or leans itself out, or surges). The pumper carb ignores the engine "pump" at lower rpm and generates its own fuel delivery with a pump. This pump squirts the fuel into the air, forcing it to stay mixed better and longer. This gives you the smoother, stronger throttle response at low rpm's. It also allows you to run a much larger carburetor size than you could have with a "regular" carburetor design. This gives you more top end power. If you ever experience bog and hit at lower rpm's, the pumper carb will make that go away. If you are someone who spends lots of time at one low throttle position (about 1/4 throttle), you probably won't like the pumper carb, becuase it will have more of a tendency to make the engine "surge". For my money, a properly set up pumper carb is the best option for a four stroke. But if you get a pumper that's not set up correctly, they are a headache. If you do purchase a pumper, make sure you get it from a performance shop that knows about how your specific engine works (like Stroker for your kawie). Don't purchase this item from a Carburetor only supplier. It probably won't be set up correctly. Actually, I'd give the same advice for any aftermarket carb purchase! Hope I answered your question without talking your ear off (or eyeballs out, as the case may be!). [/QUOTE]
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Pumper carb on KLX 300?
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