What jets should I run?

[CalebG0770]

I have a Predator 212 Gen 3 with a billet rod, 10k aluminum flywheel, 275 Superjet cam from brown box cams, flat top piston, 26lb springs, with a center exit 3 stage trumpet exhaust, full gov and oil sensor delete, oil return hole drilled out for better return.

I have a vm22 clone on it now and it runs okay but I bought a Nibbi PE24 Carb for it with a jet kit. I don’t know what jets I should run for my altitude and the build I have cause jetting carbs just ain’t my thing but I want my bike to run good so I need help. I’m 932 ft above sea level and I live in a colder climate with an average yearly temp of 48.25 degrees Fahrenheit if that helps.

any help or suggestions are appreciated thank you.

 

[Minimichael]

Notwithstanding your altitude and temperature, I'd say count on jetting upward of 110-120 for your main, and 36-38ish on your pilot, just due to your engine's size and potential for moving air. You'll also want to get used to reading spark plugs to check your mixture. In my limited experience of running this carb (on a 120cc flathead), I found the air screw's sweet spot can be a narrow window to locate by ear, but I expect you'll want to set yours a little rich, and you can confirm that better by eye and noting the plug's color. You might also find that dropping the needle clip (thereby raising the needle) will help you dial in your overall mixture, and counteract what I feel is one of this carb's downsides: a mix that's too lean at early throttle. I don't know if your 212cc will encounter the same; maybe the carb responds best under big stroke conditions and so none of this applies to a 212; or maybe 932ft of altitude dictates not going so big on your jets after all; but I note the 24 is officially rated by Nibbi for only 140-150cc. Also, the PE24 slider is pretty short and the throttle body is quite wide compared to a VM or PZ slider and throttle body, so I really get the feeling that Nibbi's wide throttle body makes it an air hog from the start. And I think this makes it difficult to suddenly richen up the mixture with all that air already rushing through upon the slightest blip, or even gentle acceleration with light throttling. So, you may find if you go generally rich on the air screw, and bigger than stock on your jets, you'll start to overcome the leaning affect of this racing carb's high airflow design. I also think that raising the needle is a key adjustment here. Last I checked, Nibbi sold only one needle size, so we should expect that adjustments of 2 or even 3 notches may be necessary to get your taper to where it needs to be for both your overall mixture and your gas flow readiness. You may find that, after enriching the carb with bigger jets and dialed-in air screw, finding the ideal position for your needle can help pre-charge your system and ensure that the slider's instant high air flow is more immediately met with gas, and in the proper quantity across the throttle's range.

Just my experience. Best of luck.