mikuni carb question

How do you know what size float needle and seat goes in the carb? I have a 430 with a 3.3. I took the carb off my 250 and it has the same thing. I can't say either carb is original to the bikes. Does anyone know where I can get info on what size my 76 cr250 would take?

3.3 is fine all that means is flow thru it to fill float bowl, when it's to the float level it is shut off.
Later George

I have a 2.0. I'm wondering if that will be ok for my 250.

Should work fine.
The thing that really matters is does it keep the float level high enough?
If you are riding on off throttle say in the woods where not going WFO for more than a second or 3. it doesn't matter. This type of riding your on the pilot jet,needle jet, 3/4 to WO is main jet this jet is the one that gulps fuel the others just sip.
But if in the desert or Baja and are pinned for miles you can starve for fuel, because the 2.0 won't flow as much fuel as a 2.5 or 3.0.
Later George