carbs being re-built....which needle kit should i purchase?

[powerbio]

i have decided to do something about the flat spot of have on my 1990 nc30.....so ive taken my carbs off and im having them stripped down...cleaned..and set up using an onboard gas-analyzer.

im running standard exhaust but with an scorpion race can cut down by 3'' and air-box/filter etc is standard.

im wanting to get larger main jets just incase it is running a bit lean top-end and a needle kit that have the grooves/circlip for adjustment.

i had found a dynojet kit...but unfortunately it has been sold. so it looks like ill buy an assortment of main jets off rick oliver but im unsure as to what make of needles to get and where from? FI? keihin?...i have a total budget of around £100 for jets and needles.

i have been researching on here for the last week but its very hard to really work out what is best etc.

many thanks
duncan

[powerbio]

so no one knows what the best needle kit is to get...or where from...or how much?

[Psychosomatic88]

Hi Duncan,

I would almost certainly call or contact Rick Oliver, as he would be best able to advise and also supply his reccomendations.

Here is a snippet from one of his documents on tuning:

" Without getting too technical, there are basically three overlapping phases in carburettor operation.
The pilot jets and airscrews control tickover and initial pickup, the needles and needle jets cover the
mid-range and the main jets take over when the throttle is fully open.
The very least that you will need to do is get the main jets right. An alternative set of needles will
improve mid-range, and there is a carb slide modification which will improve the speed of pick-up.
As I mentioned in the last magazine, early (RK) Model NC30s have 110 main jets, which need to be
changed for 115 front/118 rear as fitted to later models, or 118F/120R if you are using a race pipe.
This is a rule of thumb guide to sizes, which you can double check by giving your bike a good flat out
thrash and then having a look inside the tail pipe of the exhaust, which should be coated with a dry,
coffee-coloured deposit - if it’s white, it’s too weak, dark brown or black, too rich. (In an ideal world,
you should check the colour of the spark plugs, but this way is a lot less trouble, and accurate enough
for a road bike).
Mid-range carburetion can be improved by changing the carb needles, this will fill in the noticeable
flat spot which is present around 5 - 7,OOORPM on most NCs. I have personally tried two different
carb needle kits (both of which come complete with main jets). The first was the American-made
“Factory” kit, and must as I hate to slag off anyone’s products, I have to say that, fitted as per
instructions, it made practically no difference to the power curve, but did put fuel consumption up
from high 30s to low 20s of miles per gallon. Putting that one down to experience, I subsequently
tried a kit produced by Jonathan Collins at Cayman Products. This uses dynojet main jets and their
own custom-made needles, and it works just fine, filling in the mid-range and improving peak power
by 5BHP with a race exhaust. It would be noted that Dynojet main jets as used here are, because of
their better flow characteristics, effectively one size larger than standard Keihin jets, i.e. Dynojet 118s
are equivalent to standard 120s. Pilot jets will not need changing, just make sure that the pilot air
screw settings are as per the Workshop Manual or carb. kit instructions (usually around 2-2 X turns
out from fully seated).
The last carburettor mod. is to reduce the degree of damping on the slides to enable them to rise more
quickly when the throttle is opened. This has no effect on power, just improving throttle response, and
is achieved by increasing the size of the air bleed holes which you will find in the bottom of the carb.
slides, off to one side the needle. Remove the slide from the carb. as per the instructions in your
Manual, and extract the needle from the slide. Carefully drill out the air hole from its standard 2mms.
to 2.5mms, blow out any swarf and reassemble the carbs."

My jetting on my RVF is 145's for the front and 148's for the rears, but im using a modified airbox and filter, modified induction ducting, full race system and HRC carbies. We all have different parts fitted and different needs, but im sure Rick can put you straight.

By the way, which part of glos are you from?

[powerbio]

cheers for the reply mate....

i have spoken to rick oliver....he has suggested the main jet sizes i will need (im going to order standard jets, sizes - 120 x2 and 122 x2 and already having standard jets at 118.....i can make up combos of either 118f 120r or 120f 122r).

rick suggested FI international needle kits to sort out my mid-range flat spot....but im not sure where to get them from or how much?...i have looked on the net and ive phoned elliots who basically refused to sell me any on the premises that adjusting the needles wont help with the mid-range flat spot!



i live in tewkesbury.....

thanks
duncan

[Psychosomatic88]

In which case I would...

1-Order bits from Rick that he reccomends if you havent already done so
2-Road test the new settings

Then you can either a- Shim the needles, (I know a few people who have done this and report success, not total but much improved, certainly good enough for road use) to IIRC 0.5mm or b) or re-ring them up later but dont state what they are for... remeber that Rick is basically a V4 honda God and his word is above all others on the matter

Tewkesbury isnt terribly far away from myself or a few other forum members actually. Im from Lydney, but am usually gloucester way, in fact, im off up there now :D

[powerbio]

hi


rick has said to get some FI needles...its good to have the ability to adjust the needle height....i guess ill have to order them from elliots without saying too much to them! any ideas of cost?

when the weather is better we will have to meet up

cheers

[Cammo]

rick has said to get some FI needles...its good to have the ability to adjust the needle height....

You'll get pretty similar results just by raising the needles with a 0.5mm washer, it fixes the midrange up nicely. The nc30 has one 0.5mm washer as standard, add another to it to make a total of 1.0mm.

The standard needles are adjustable, just add more washers...

[powerbio]

hi,

thanks for the reply......the guy doing the work on my carbs knows about shimming the needles but he doesnt want to do that....he has said when you buy a kit, you usually get a guide for what 'groove' to have the circlip at according to what set-up you have...making it an easier starting point.

thanks

[Cammo]

thanks for the reply......the guy doing the work on my carbs knows about shimming the needles but he doesnt want to do that....he has said when you buy a kit, you usually get a guide for what 'groove' to have the circlip at according to what set-up you have...making it an easier starting point.

Meh, it's your money.

I've had FI and a few other sorts of needles, raising the standard ones by 0.5mm is near as identical to the performnace the aftermarket ones give.