Standard NC30 jet sizes?

[SimNC30]

I've taken my carbs off to give them a clean as my bike has an intermittent fueling problem. They look pretty clean, but have nonetheless been blasted through with an airline to clear out any blockages, of which there seem to be none. I've noticed that two of the float springs aren't that springy anymore - if you tap the floats they either stay down or don't rebound very quickly at all. I'll be replacing those tonight as i'm assuming that if they aren't working exactly as they should be then they'll be a contributing factor to my fueling issue. What i'd like to know is what size are the standard main jets meant to be? On my carbs the rear two cylinders are running 120 jets and the front two are on 122s. Is that correct? It seems strange to me that they aren't all running with the same size jets.

Cheers,

Si

[VtypeV4]

I could be wrong but i thought the stock settings were 120 rear 118 front. Mine has 120 fronts and 122 rears. They run the rears a little richer as they don't apparently get as good cooling. It supposedly smoothes the power delivery out a bit too.

[CMSMJ1]

Stock on a K model - 1989 was 110 all round IIRC

the later models were 115F and 118R

Common mods for people with pipes who follow the crowd are to put 118F and 120R

The rear cylinders, being hotter, run a richer mix to help keep them cooler.

[SimNC30]

Stock on a K model - 1989 was 110 all round IIRC

the later models were 115F and 118R

Common mods for people with pipes who follow the crowd are to put 118F and 120R

The rear cylinders, being hotter, run a richer mix to help keep them cooler.

The guy who had the bike before me put an end can on (he told me it's a full system, but I don't think so) and i reckon he just assumed the jetting needed to be changed for larger jet - so he just put massive ones in that made it run badly. My bike is a 1991 NC30, is it a K-model then? I've spoken to someone at a dyno near me who knows these bikes and his advice was to start with 110s in the front and slightly larger jets in the rear two cylinders, so i think i am going to go from there - it's justt such a pain in the arse getting the carbs on and off.

I stripped the carbs off last Sunday night and cleaned them. Getting the bottom part of the airbox off along was more work than it should have been becasue the heads in every screw were mashed beyond belief, so each one had to be drilled out. I left the bike like that Sunday night as it was getting late and put the carbs back on Monday evening. Once i got the bike running again it was even worse! I assume this is because if the jets are too big in the first place and then i've cleaned my carbs so they are more efficient, then they were letting even more fuel through once they'd been cleaned. Nightmare! I will be getting some smaller jets very soon to see how the bike responds.

Out of interest - what exhaust modifications have you guys got on yours? Full systems, just a can etc, and what jets do you use, if not the standard ones?

[Cammo]

Common mods for people with pipes who follow the crowd are to put 118F and 120R

My bike is a 1991 NC30, is it a K-model then? I've spoken to someone at a dyno near me who knows these bikes and his advice was to start with 110s in the front and slightly larger jets in the rear two cylinders, so i think i am going to go from there

Bad idea. They run very lean on 110's, so lean that they don't always rev out with some pipe mods. Your bike isn't a K model, so 115f/118r is standard jetting for it, you don't want to go lower than standard especially with a pipe on it.

Stick with CMSMJ's jet size suggestion above, it's tried and proven!

[CMSMJ1]

Ref jetting I use

No9 - Has RVF carbs and a half system, no airbox lid but std filter - runs 130 main jets and loves it.

Race bike - Has VFR carbs, full system and std airbox - runs 118/120 and is too lean.

I'll be fitting my wannabe HRC carbs with 145/147 jets, no filter and see hoe that goes...badly for starters I guess..lol

110 was lean on std can so stay away from that. 118/120 will be right for you or close enough