jetting

How to know which of the 4 carbs on my motorcycle needs the rejetting or if it needs some sync?

I'm racing snowmobile this summer in iwa watercross and I need to kno as much as possible about changing the jetting and Wat weather is for Wat jets

I am putting a 1979 rotax 503 fan cooled engine in a go kart for summertime use and I'm wondering what the correct jetting would be? Much leaner I would assume, but how much? Temperature to be around 70-80 degrees.

I am putting a 1979 rotax 503 fan cooled engine in a go kart for summertime use and I'm wondering what the correct jetting would be? Much leaner I would assume, but how much? Temperature to be around 70-80 degrees.

i have a yz250f 2002 that wont stop back fireing. the engine is completly standard. i think the jetting is a little lean. i dont have a clue a bout the new 4 strokes. i mean i know every thing there is to know about two strokes but 4 stokes. could you please tell me how to change the jetting...

...and putting a set of micron gp pipes? rd350 jetting problem