I have no idea for fuelling on a 33hp restrcited NC.

The pilot screws only affect the bike at idle revs and just off idle, no more than that.

What revs are you having issues at?

Hi Cammo, thanks for the great guide, i'm using it atm to set up my carbs.
I've now realised that my carbs are UK spec as the needles in were J1GA and J1GB, there were no washers under the needles so i have put a 1mm washer under each, also the jets in it were 115F and 117.5R so i have changed these to 120F and 122R.
With the UK slides being different, do you suggest still drilling out the 2mm hole to 2.5mm?
Currently they have a 2mm hole but also have a 1mm hole which is 2mm countersunk, see pic below.

Previously the bike had poor throttle response, when trying to accelerate hard the bike would bog down for 5 seconds or so before actually accelerating. Also there was a flat spot between 8-9k revs, the bike revs fine before 8k revs and fine after 9k revs, but really struggles inbetween.
However i've just took the carbs apart and found one of the front jets had unscrewed out of the emulsion tube completely and the other front emulsion tube wasn't screwed in tightly, so obviously this would have had a bad effect.
Any help would be much appreciated
Cheers, Richie

TheRehabKid wrote:With the UK slides being different, do you suggest still drilling out the 2mm hole to 2.5mm?

Hi mate, no I wouldn't suggest drilling them out any further, it looks as though the extra hole will act in a similar way to a larger hole. I haven't always drilled them out on my jap spec carbs, it doesn't make a world of difference (but every little bit counts I guess).

TheRehabKid wrote:I've now realised that my carbs are UK spec as the needles in were J1GA and J1GB

It might be worth checking that you have these needles in the right carbs. In the Jap spec carbs, 'A' needles go in rear carbs, 'B' needles in front carbs. I don't know if this is true for UK needles. The difference in the 2 Jap spec needles is about 0.5mm in total length, the shorter (richer) needles go in the rear carbs. You could follow this logic to determine which needles go in which of your UK carbs. Let us know the result, there's not a whole lot of info out there on the UK carbs!

Your jet sizes sound fine, though it might be an idea to try the carbs with the 1mm washer and with only a standard 0.5mm washer, checking the performance of each at about 5-7k rpm. The UK needles may be richer already than the jap spec needles and may not like being raised further.

Let us know how it goes.

Cammo wrote:

TheRehabKid wrote:With the UK slides being different, do you suggest still drilling out the 2mm hole to 2.5mm?

Hi mate, no I wouldn't suggest drilling them out any further, it looks as though the extra hole will act in a similar way to a larger hole. I haven't always drilled them out on my jap spec carbs, it doesn't make a world of difference (but every little bit counts I guess).

Your jet sizes sound fine, though it might be an idea to try the carbs with the 1mm washer and with only a standard 0.5mm washer, checking the performance of each at about 5-7k rpm. The UK needles may be richer already than the jap spec needles and may not like being raised further.

Let us know how it goes.

the midrange problem could also be caused by being over rich, (to much fuel flooding the cylinder) which im currently trying to solve so also bare that in mind that raising 1mm may be making it worse, try dropping them out and see, try the 0.5mm also, but with carbs ive found its best to one thing at a time then you know if its better or worse and whats caused it etc

Hello,

I am in the process of seeing what I got in the 400 I just bought. Pulled off the carbs as it was running terrible and big trouble starting.

All jets and emulsion tubes blocked, gauze under the float needle had crap in it etc etc.

Bike is Standard 89 NC30 (I believe), does not need key to run, megacycle exhaust, HRC tray, No air filter, standard rubber trumpets

I found the following and hoping someone can suggest why the previous owner may have done this.

Main Jets: 125/125 (There was 125 stamped on the top, they are round have groove around outside edge but do not have the keihin star stamped on as the pilot jets do.

Pilot Jets: 35/35

Washer under slide needles: He put 1 * 1.5mm spring washer (6mm diameter) AND 1 * 1.0mm Spring washer(4mm diameter) as well as the standard 0.5mm washer.

The slides had the std 2mm hole in them.

.......

Any ideas for this genius's theories please ???

999Gomerz wrote:Any ideas for this genius's theories please ???

Err yeah, the previous owner thought this would be a fully sick setup bro?!

I would be very surprised if that runs properly at all. Those jets are way too small for that type of open carb setup. I've seen heaps of race bike's carbs butchered like this. I just sit back and wait for them to pass the bike on cheap when the owner can't get it to run properly....

It would be easiest to return it to a standard type setup IMO, it will certainly run better than it currently does. Fit an nc30 airbox and a genuine honda filter, and remove the hrc tray. Fit 120/122 main jets and use a total of 1.0mm washer on the needles. That would be a great start.

RB racing (Sydney) can usually help with parts, or try the classifieds here on the forum.
http://www.rbimports.com.au/

Cammo wrote:

999Gomerz wrote:Any ideas for this genius's theories please ???

Err yeah, the previous owner thought this would be a fully sick setup bro?!

I would be very surprised if that runs properly at all. Those jets are way too small for that type of open carb setup. I've seen heaps of race bike's carbs butchered like this. I just sit back and wait for them to pass the bike on cheap when the owner can't get it to run properly....

It would be easiest to return it to a standard type setup IMO, it will certainly run better than it currently does. Fit an nc30 airbox and a genuine honda filter, and remove the hrc tray. Fit 120/122 main jets and use a total of 1.0mm washer on the needles. That would be a great start.

RB racing (Sydney) can usually help with parts, or try the classifieds here on the forum.
http://www.rbimports.com.au/

Thanks Cammo,

Happy to put it back to a known value and then see how it goes.

I have the NC30 airbox (minus the scoop at the front)

i don't have:

- The air cleaner inlet duct (part numbe 3 from this diagram) http://www.akhara.com/nc30/nc30parts/files/35.htm
- The rubber flappy bit asembly that directs air from above the rad to somewhere near the carbs. I think part number 5 in this image http://www.akhara.com/nc30/nc30parts/files/51.htm

My questions are:

1- Would it be easier to continue oon the HRC tray route? What would I need?

2- Do I need the rubber flappy bits and the inlet duct for the oem airbox?

Cheers,

Thanks for the great write up.

I wonder if i could get some information please

after a year of tinkering in spare time, now have my NC30 engine with NC35 carbs fitted, dynoed today it was making 66.18bhp after jet changes ect up from 58bhp previous test and torque well up as well, but what it was showing was that it was running still too rich across the whole test really, NC35 carbs fitted with RO jet kits i used the middle needles B's all round, holes drilled to 2.5mm, new springs, 1x 0.5 washer under each. jets down to 118 all round, started at 140's!! but 118 showed best resualt on dyno (appreciate on track might be going up to around 120, 122, 124's), No air filter being used instead using fine metal gorge and RO program CDI.

Can anyone shed some light on which needle does what as standard i.e A needle, B needle and C needle and to which one is the richest and which would be the leanest so we can look at what steps to take to improve fueling again and can anyone PM me with some helpful information on fitting a TPS sensor as well please and which ones will fit the RVF carbs?

Thanks Guys

James

999Gomerz wrote: 1- Would it be easier to continue oon the HRC tray route? What would I need?

Do you mean the full hrc open carb setup?

You'll need a replica hrc jet kit (from Rick Oliver) and you'll need to restrict the air jets as the nc30 hrc velocity stacks (which shroud the air jet) are no longer available. Not difficult, but some trial and error involved in finding the right restrictor/main jet size. Check out Jim's build thread for some info on a replica hrc setup: viewtopic.php?f=62&t=23105&start=30

Good info also at Mike's site: http://www.akhara.com/nc30/nc30hrccarb/index.html

2- Do I need the rubber flappy bits and the inlet duct for the oem airbox?

Difficult to say for a track bike. Certainly a must for a road bike if you want ease of carb set up, both of these parts are critical, many threads on here about problems when these are removed! I think it would be a good idea to try and get hold of both parts. Your setup is so out of whack currently that having these parts will get a much better result much quicker than without them!

jamesvfr wrote:Can anyone shed some light on which needle does what as standard i.e A needle, B needle and C needle and to which one is the richest and which would be the leanest so we can look at what steps to take to improve fueling

Good result.

Take a look at the nc35 kit manual, I believe Rick's needles are based on measurements of the hrc needles. You can find a copy here: http://www.400greybike.com/docs.htm

It lists the needle diameters on page 1-5. 'A' is thinnest (richer), 'C' is thickest (leaner).

Not sure that drilling the slides is a good idea, a better option is to use only the hrc springs. This is potentially richening up your midrange too much.

Best also to stick with the standard sized (#35) pilot jets, any bigger can richen up the rev range. I agree with your thinking that you may need bigger main jets when tested at speed on track. Let us know how you go.

HTH