NC30 carby jetting - DIY guide

[Mananon]

Not enough to stop it firing Geoff but it just won't be quite on song.
What it does mean is that someone has played with the carbs in the past so check everything.

[uber pikey]

A personal thank you to Cammo for this thread, I was in two minds to buy my mates VFR 4 as it hasn't been run for 10 years, the thing started but that was it, it died and wouldn't fire again, I stripped the carbs re-jetted with the standard set up, set the pilot and also set the butterfly's and choke up. It runs a treat and am looking forward to it's MOT and 100mile ride home through Wales.

[Cammo]

No worries mate, glad it was of some use to you.

Enjoy the ride!

[dom-tune]

hi just stripped some carbs i got from a local yard and this is what i got


NSF ................. OSF .................. NSR ............. OSR
122 MAINS ....... 122 MAINS ............. 120 MAINS ........... 120 MAINS
4 HOLE ............. 4 HOLE ............... 5 HOLE BUT THE 5TH IS TO THE SIDE SAME AS
J1GA NEEDLE .................................. J1GB NEEDLE
NO WASHERS UNDER NEEDLE .
2 HOLES IN PISTON ONE LARGE ONE SMALL NOT INCLUDING THE ONE THE NEEDLE POKES OUT OF.

What do you think the carbs look mint inside .i take it the mains are ass about face but whats going on with the
needles (ie no washers )any help would be very welcome
Regards Dom

[Cammo]

Yeah does sound a bit stuffed up. Usually it's just because someone before you has had a crack at some home maintenance.

Sounds like you just need to change the main jets and needles around to the correct carbs, and stick a washer under each needle. I assume you mean J51A & B for the needles, if not then they're not NC30 needles!

Post a pic up of the holes in the slides if you want some further info, it sounds like a previous owner has drilled an extra hole.

[dom-tune]

thanks cammo, defo J1GA J1GB needles ,the holes in the slides are one hole is counter bored down about 2 mm to an approx 1mm hole the other hole is about 2mm all the way down .they are in very good condition. i have the carbs that are on the bike should i try the needles out of those or just put the new ones the right way round and try it on the bike ?
regards Dom

[Cammo]

defo J1GA J1GB needles ,the holes in the slides are one hole is counter bored down about 2 mm to an approx 1mm hole the other hole is about 2mm all the way down

My bad mate, J1G needles are uk spec, sounds like you have a set of UK spec carbs (your jet size is also standard uk size). A needles go in the rear carbs, B in the front, and they should still have a washer underneath them (you won't be doing the bike any favours by not fitting some!).

The other big change to the uk carbs is that they have metal (instead of plastic) slides. The holes in them are probably different also which may explain yours.

[dom-tune]

thanks again cammo, yes they are metal slides one or two washer under needle what do you think?
cheers Dom

[Cammo]

1 washer is standard, I would only stick another washer in if the bike feels to have a weak spot from about 4-7k rpm.

No harm in trying both if you want to see what difference it will make.

[dom-tune]

will do, removed the old carbs and found the rubbers are shot new ones needed so will not be runing for abit . will let you know when i get it runing