Carb suggestions please!

[Smev]

I am stuck as to how to set up the carbs on my NC30.

I have fitted a Yamamoto half system, carbon fibre air tray and done the needle raising mod. However.....

When accelerating, most noticably in 1st gear, the bike seems to bog down and it sounds quite raspy too.(almost like a 2 stroke!!)

Does anyone know what needles or jets would be good for this set-up?

Basically as a starting point?

Thanks
Smev

[royster81]

more info needed i'm afraid ,are you running a fliter,what mods have you done to the airbox,what jets are in at the minute,when it sounds raspy where abouts on the rev range are you,does it hesitate at all

when you say you fitted the scoop did you just put it under the carbs and remove the front flap above the radiator and leave the airbox alone ?

[Smev]

ok heres the extra info,

I did just remove the flap and fit the HRC style tray, the std filter is still fitted.

I believe it does have the std needles and jets.

It hesitates/splutters/bogs down in the mid range - 4000 to about 9 or 10,000.

Hope this will be of more use?!

Tried a local dyno place for info today but they were closed

[CMSMJ1]

The needles are your main tuners for the midrange ..so I would stick them back to srandard mate and go from there.

Remoc-ving that flap can cause poor response as the air is not as still as the bike would like. Does the airbox have a snorkle still?

[Smev]

I'll try the needles back to standard first - and see how it goes.

The snorkel is still fitted to the top part of the air box as I thought it would still be needed. I have several spare ones too, to try things out!

I guess dyno time helps but can be expensive

Thanks for the pointers though :)

[Cammo]

Removing the flap will probably be responsible for most of your symptoms, the air tray might also be contributing. I would replace these back to standard, and jet the carbs.

Raising the needles won't do much harm, I've only ever had good results. 118 front and 120 rear would be a good start regarding jetting, also check that the pilot screws are set correctly (2.25 turns out).

[superlite]

I have fitted a Yamamoto half system, and it sounds quite raspy too.(almost like a 2 stroke!!)

My old Yamamoto sounded exactly the same - I think it's something to do with resonance. It's not related to your carb set-up though.

[Smev]

Thanks for the advice guys,

I'll be giving them a go later - after the moto gp :D

I thought about trying to re-pack the end can, or re-do the joins with some exhaust paste making more of a seal - that could possibly help with the raspyness!

I'll also try it back to std wth the flappy piece.

Once I've checked the carbs to see what needles are fitted I'll try some 118's and 120's

Cheers All!!

[royster81]

my castrol bike runs a similar set up,
i have the airtray fitted and the filter base unmodified (so it still comes forward to the headstock),the snorkel is still fitted as is a filter
jets are 116/118 and 0.5mm shim under the needle,A/F screw 2.5turns,2.5mm slide hole

to be honest i think the only thing the hrc tray on the castrol bike is doing is circlulating a bit of cold air around the carbs and maybe shielding them from the hot motor,when i rised the needles the bike hated it and ran similar to what you are saying,needles back to standard first and see how that goes

the hrc tray on the track bike is a different matter but .....

[Smev]

Right - had my carbs in pieces last night -

Found that the carbs were running 115 front, 118 rear jets The slides hadn't been drilled and the needles only have the original thin washers underneath them.

I've also removed the HRC style tray and put the std air tray back on.

Hopefully it'll run better when its all back together now.