Main jet size for a NC23

[The Novice]

from what you say i think they need turning in a bit, cant remember the revs hanging but i will have to check, will give it a go and let u know how i get on..... not sure when i will get to do it tho as its about -2 in the garage !! I love this site, someone always knows the answer or can lend some advice, invaluable when you aint got cash for a mechanic!

[The Novice]

Had the carbs off again, cleaned them all up. Out of interest the jet sizes in mine are 110. its an nc23rrj, haynes manual says should be 115, i am not up on the jetting think but i assume these are ok with stainless headers and a slip on. Anyone else havea comment on the jet size? should i be concerned?

I turned the pilot screws in half a turn, i did check and they are turned out 2 full turns now, haynes manual says 2.5 turns (which is what i set them to last time i had them off), again i assume the jets, headers and slip on meant it needed leaning off a bit from honda recommended settings?

Anyway sealed the float bowls again with hylomar and jobs a good un !

I then balanced the carbs with a carbtune pro i bought last weekend. It was pretty easy, bit fiddly but saved me a garage bill. Did try and take a video but my phone wouldnt work for some reason so i concentrated on the bike!

Just need to fianlly get the brakes done (i have had loads of issues with them so far) and i can take it for a spin to check if its behaving now.

[c7ll]

I will have a fully rebuilt set of nc23 calipers fe sale soon if you're interested.

Cheers,


C

[Wozza]

Aftermarket can means you should be upjetting from standard, not downjetting. You may have Dynojets but they still wouldn't equal 115 Keihin jets. I would fit 115s and get it on a dyno.

[The Novice]

I did wonder that, I wasn't sure if bigger numbers meant bigger jet or vice versa if that makes sense. I am not sure what jets they are, they just said 110 and had a little star on them? I will leave as it is for the moment till it's roadworthy again and see how it runs before I strip it down again.

[Wozza]

They will be Keihin (standard) jets then. You really don't want to be running smaller jets than you should as the engine will run lean, leading to burnt valves and pistons - bye bye engine.

I imagine someone in the past has wanted to fit standard jets and has mistakenly put the 110s in, or at some point the carbs have been replaced with standard K model carbs. You could check the carb number - VG04A is J, VG04B is K.

Have you checked the colour of the spark plugs?

[The Novice]

Last time i checked they were fairly black - hence thought running rich - which to me would point to them being k as if they were j you wouldnt expect 110's to make it run rich.

I am not too sure about the carbs, I def need to check if they they are J or K model because as you say, makes a big difference. Where are the codes for the carb, doesnt tell you in the haynes..... please dont say underneath, they need to come off....

[Wozza]

I don't know where the numbers are, sorry. I would've though on the side somewhere.

You say yours is a J model - how have you verified this? If by the frame number, I would check your engine number - you never know, you might have a K engine hence the K size main jets.

The main jet affects the top end of the revs. So, if the bike is running rich at low revs, and you spend most of the time riding at low and mid revs, looking at the plugs won't help unless you go for a ride keeping the revs high, then kill the engine from high revs and immediately check the plugs. Personally I wouldn't bother. If you use the method I described in my second post in this thread, and you cannot tell a difference in acceleration between WOT and gradual opening of the throttle at the top end of the revs, and there are no flat spots, then you are not far out on the main jet. Mid range revs are affected by needle height, low end revs are affected by pilot screw and float height. To progress from this stage you need an AFR reading which means getting on a dyno. Check in advance that the dyno place will provide you with a printout of the AFR reading with the power/torque graph.

This is a good website if you fancy a bit of reading:
http://www.factorypro.com/tech_tuning_p ... gines.html

[The Novice]

Thanks, first things first, i will check the frame and engine numbers, and carbs if i can find the numbers when i get home from work.

If its a k - and fingers crossed it is, then the jet in there will be fine, if not i need new ones.

Its an f reg, 88 - so i just assumed its a rrj.

[Wozza]

If its a k - and fingers crossed it is, then the jet in there will be fine, if not i need new ones.

Fine for a bike with standard exhaust system. In theory yours would still need to be larger, but there's only one way of knowing for sure...