NC30 carby jetting - DIY guide

[Cammo]

hey guys ive checked everything and am still having the same problems as per this post viewtopic.php?f=24&t=40192.

but the bikes been sttutering at high revs when the bikes warmed up.

That's a typical symptom of the main jets being too lean.

Fit 118 front, 120 rear and it should be improved. 110 size jets are too lean on standard bikes let alone one with an aftermarket end can.

[Jac-al]

i reckon that should work, wont sea level or the climate here play a role?

[Cammo]

i reckon that should work, wont sea level or the climate here play a role?

Nope.

We have similar weather here in Australia and also have a sea level...

[Jac-al]

ok, thanks, gonna get new jets today

[CMSMJ1]

JO'burg is several thousand feet up though..so it will matter. But hey, swapping jets is fun and going between rich and lean will give you a good feel for it.

[Jac-al]

being several thousand feet above as u say would mean i would need to go lower than u on the jets sizes wouldnt it?

[CMSMJ1]

Yes -you have lower air pressure and so less oxygen to burn with your fuel - so you need to run leaner.

[vfrman]

If you put a freer flowing exhaust on AND went smaller on the jets then I would bet you are right, it is too lean even at a higher altitude.

[Jac-al]

im confused, putting smaller jets would make it run even leaner

[Drunkn Munky]

im confused, putting smaller jets would make it run even leaner

Yes, in simple terms where you live you have less air going into the engine so you need less fuel to balance the mixture out hence you want smaller jets.

You could go the other way i spose and try to get more air into the engine but Nc's tend to be very temperamental when you start messing with the air intake yet living in an area of low air pressure it may work for you.