NC30 base carb setting without air filter etc

[james66]

Hi all

Has anyone got some sort of base jetting + needle heights for nc30 carbs, 4-1 system, Just airbox + snorkel, no air restrictor or filter etc

Cheers
James

[thunderace]

You really 100% sure you want to run an NC30 without an air filter? It'll run like shit unless you spend a fortune on a race setup.

[james66]

Any bike with carbs will run shit if filter just removed due to upsetting the AFR + its just down to correcting the fuelling + will be ok again, nc's are no different, No filter or air restrictor is pretty much the beginnings of a race setup, none of the so-called race setups cost a fortune, I think alot of people get suckered in to believing they need that that + that

If main air jets are blocked off it helps alot in the midrange dip

Ive also got a huge airbox that the carbs sit in which has a scoop coming to the front which will be going on very soon
It is on my race bike, i just wondered if anyone had a rough setup so i could get it close'ish before snetterton next weekend as there as a dyna-pro dyno there

cheers

[Drunkn Munky]

Has anyone got some sort of base jetting + needle heights for nc30 carbs, 4-1 system, Just airbox + snorkel, no air restrictor or filter etc

That wont work, bin the airbox altogether and fit a carb tray, cut down the stacks and restrict the air jet or fit HRC rep stacks. You can try 1mm washers under the needles and obviously massive jets 140+ as a start point but with something as major as that id be checking it on the dyno.

[james66]

It does work, the RLR system is pretty much that except there is a scoop that comes down over the rad

Dont need massive mains if MAJ is blocked off
We have a 35 with RLR air box lid no filter etc + thats only running 98 mains

Will be finished + set on a dyno but we only have setups like it for 35 carbs, I just need something so i can get a roughish run on dyno so we have a starting point

Drunkn Munky - what sort of results have you had with the Air tray? Ive got one of them here aswell but never realy been interested in trying it

James

[Drunkn Munky]

It does work, the RLR system is pretty much that except there is a scoop that comes down over the rad

Well that makes a big difference and the RLR setups are ram air based with carbs modified to suit

98 mains, ive never heard of a setup running such small mains. Ive had 2 RVF RLR ram air setups and both were running 140+ mains hence why they need a fuel pump to keep up.

[james66]

Ram air is irrelevant on 99% of dyno's as there are very very few with air feed fans that run according to wheel speed

The only modification to carbs for Ram air are to run the float bowl breather into the air box + closed off main air jet, closing the main air jet allows the use off much smaller mains
If the float bowl breather does not go into the airbox then there is a lower pressure in the float bowl than the venturi on the carb + the fuel wouldnt get out of the float bowl when upto speed

The fuel pump has nothing to do with keeping up with the 140 mains its because the fuel wouldnt get into the float bowls if by normal gravity fed due to the bowl pressure so it has to be pumped

[Cammo]

With no air filter or air jet restriction you'll need around 160 mains on nc30 carbs. But it'll run like a turd because the fuelling transition from needle to main jet is too much, seen this countless times.

As you say you'll get a far better power curve if you restrict the air jets. I've only ever used the HRC velocity stacks which reduce the amount of air getting into the air jet, for that sort of setup I used 145 mains. Rick Oliver sells replica stacks if you want to go down that route.

I'm not sure what sized jets to use if you block off the air jet completely but it would certainly work once the mains were sorted. I would start with a conservative (rich) size an go from there. 125's would probably be a safe bet but I really have no idea.

Let us know what you end up using.

[Drunkn Munky]

Well you seem to know more than us so let us know how you get on as i for one will find the information usefull.

[thunderace]

its just down to correcting the fuelling + will be ok again, nc's are no different

Yes OK, if you say so You do need a proper set up on any bike to prevent ingress of nasties if nothing else.

But you obviously know a lot more than we do, even the seasoned racers among us, so get on with it and let us know how much the re-build costs you when your engine has swallowed something it shouldn't.