My NC30 is running quite rich. I've got an Ethos 1/2 system with a Tyga C/F end can. The carbs are running 118f and 120r with needles shimmed to 1mm, & slides drilled. Standard airbox. Any suggestions of the best way to lean her out a bit? I've had it dynoed and its way down on power ( 50bhp) as a result of the richness.

Fit the right jets....

" Fit the right jets"

Does this mean I go bigger on the mains, like 120/122? Surely this will only affect the upper revs. She's rich all over.

Have you got a dyno graph we can see?

If it is rich all over how healthy is your air filter? Might be time for a new one?

If not then you'll wnt smaller jets and to go back to 0.5mm washer under the needle.

115/118 might be a start - depends how rich.

Did the Dyno operator not offer any advice?

I don't have the graph to hand, but the air filter is only about 6 months old.
I only had a power run done and the fuelling was about 11.5 -12 all the way through. i'll remove the .5mm washers and see.
The only advice from the operator was maybe bigger jets??

emto wrote:The only advice from the operator was maybe bigger jets??

That'll make it richer. I'm confused?!

You're confused? I don't know where the dyno operator was coming from.
I think I'll remove the extra washers and bring the mains back to 115/118 & see what happens.
I'm in Ireland so my dyno options are limited, but I've just dropped my current operator.
Thanks for the input & happy new year.

Removing the washer will lean out the mid-range slightly.. around 6-9000rpm you'll see a difference at.

Firstly, check you pilot screws are set properly... when did you last check the valve clearnances?

Finally, smaller jets will help top end richness

There's an excellent set of CV carb tuning instructions on the Factory Pro web site:

http://www.factorypro.com/tech/carbtun.html" onclick="window.open(this.href);return false;

Main Jet size will effect fuelling over the entire range, not just the top end. Before you start adjusting things to "see what happens" check your plugs, your air filter is clean, valves correctly adjusted as suggested, your carbs are clean and the float height settings correct. Then find the best size Main Jets for WOT performance (I did not suggest you do this on a public road ) and proceed from there. There's a bit involved but it's not rocket science (ie if I can do it anyone else can), however it is time consuming. Take your time & adjust one thing at a time.

JB wrote: Main Jet size will effect fuelling over the entire range, not just the top end.

That's just plain untrue. Pilot jet size affects the whole rev range, but you don't need to deviate from standard size (#35) for most road nc's.

Emto: If your a/f ratio is 11.5-12 at the top end then this suggests it is running a bit rich (12.5-13 is what you should be aiming for - depending on gear/load). I think you're on the right track trying 115/118 jets. Your engine could be down on power due to condition also.