Carburetor Tuning Basics
People often contact us about feeling like their watercraft is bogging or feeling sluggish. Bogging is often a symptom that results when the carburetor is not properly tuned. Many people feel that bogging is caused when the carburetor is running rich (i.e., the engine is getting to much fuel); however, bogging may also indicate a that the carburetor is actually running too lean (i.e., not letting enough fuel to pass.) How does one know which problem they have?
The answer is relatively simple... if, from a dead stop, you apply full throttle and it seems to take a few seconds to clear out before the watercraft goes, then the carburetor is running rich. If after idling or running at low RPMs and it dies when you apply full throttle, then the carburetor is running lean on either the low adjuster or the pop-off circuit.
Properly tuning a carburetor is based on trial and error, good instincts, and tuning experience.
A good indicator for what your tuning requirements are for low jet and/or pop-off circuits depends on where your low screw ends up. If your watercraft runs best with low screw all the way in, then you likely need to raise your pop-off. Alternatively, if your watercraft runs best with the low screw all the way out, then you need to drop your pop-off or install bigger low jet. It's been our experience that on larger bore carburetors, the pop-off and low jet can be tuned interchangeably. However, we have also found that on smaller bore (38 and 40 mm) carburetors, pop-off changes does little to change tuning. Low jet changes on small bore carburetors seems to be the most effective tuning method.
For high jet and adjuster tuning, ALWAYS START RICH and slowly lean it out! You can very easily detonate an engine if lean. The proper method for tuning high speed circuit is by dropping RPMs. The way we do it is by finding the "sweet spot" where the peak RPMs are the highest and then doing a plug chop to read the plugs. You can go online and find a 2-stroke plug reading chart to fine tune your watercraft for optimum performance.
Text by Watercraft Tuning Tips and Tricks
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