Jet size for CNS carb?

Hi. Today im wondering, Why does everyone change to a 0.68mm jet it seems? Is that just people using the stock or speed carb? Does nobody jet to a bigger jet?

On my other bike (Fat cat exhaust, CNS carb, 80cc ZB motor), I had to rejet to 0.73 and I still need to blip the choke sometimes up hills to keep it from sputtering (well, 4 stroken really) Thinking of getting 0.74/0.75mm jets to try out next. Can't understand 0.68, it would be wayyy to lean.

New bike, Stock jet, I had the E-clip 2nd to the bottom (Needle raised, Rich)
it was 4 stroken about half the time, a little less after it warmed up, and engaging the choke killed them motor right quick with no improvement. assumed it was running too rich due to choke killing motor. Raise the E-clip to lean it out and.. its 4 stroken a LOT and almost never going into 2 stroke. Gonna try my left over 0.72 in it.. and likey order some 74/75's tomarrow.
(Note, e-clip near bottom with stock jet was fine with stock exhaust, but its **** with new SBP exhaust)

Maybe this jet problem is the reason why people think CNS carbs suck?

Allready checked for air leaks, And trust me, Running too lean CAN cause 4 stroken, just like running too rich will. No idea why, other then during 4 stroking, the air/fuel charge is not ignited every revolution, so there may be left over charge for the next cycle.

Moved to a 0.72 jet in my 2nd bike (biggest I had) and the 4 stroken is nearly gone at the exact same needle settings it was 4 stroken at with the stock 0.70.

I don't get what you mean by 'conditions not predictable'.
I make it more rich by moving needle up, It runs better.
I make it more lean by moving needle down, it runs like crap
I make it more rich by bigger jet, it runs better.

The only thing thats not predictable is the fact the choke on this carb seems to kill the motor outright when turned on, Where as my other CNS carb equiped bike that runs a little lean, it actualy makes it go from 4 stroken to 2 stroken, when used just right (Short blip on then off again)

Masterm222: I got my jets from the local motorbike parts place.. Took me awhile going through the catalog to find em however.

The package states this:
Importations Thabault ltee
Gicleur 72 BW's/Zuma
2344000 (for the 0.72)
2344070 (for the 0.70)
Theres lots of other sizes too.. I ordered in a 68, 70, 71, 72, 73, and just recently, 74, 75 and 78 (No 76/77 available?)

While the stock exhaust ran OK with the 0.70 in the CNS carb, Both my bikes after upgrading to expansion exhausts needed a 72 or 73 to even begin running well. I think I gotta up one of my bikes from 73 to 74 or even 75, since it still 4 strokes up hills now and then unless I blip the choke.

If anyone wants, I can check the catalog at the motorbike place when I go to pick up the jets I ordered in a week or two, to tell exactly what brand/model they are.

No idea on dealer, the place I went to was a second hand motorbike dealer slash repair shop.

a REALLY secure vise + two peices of wood on the jaws can bend pipes (And even expansion chambers) a degree or two without crimping them badly.

Sand+heat works much better however, especialy for anything past the most minor bending.