NC30 carby jetting - DIY guide

[Jac-al]

so whys everybody telling me to put in 118/120's when std was 115/118

[bikemonkey]

Because you have a free-er flowing exhaust than standard.

[CMSMJ1]

so whys everybody telling me to put in 118/120's when std was 115/118

Not many people actually "know" what they are on about.. some of it is parrot fashion to be totally blunt.

Your ideal fix is to get a dyno run for the air/fuel graph - you will categorically know whether it is lean or rich.

The set of the pants, in my experience -
very lean - it has no power, runs shit and just cannot rev out
lean - will rev out, still lacking power but seems to make the right noises and is almost clean
rich - will rev out but is not clean with it - sooty exhaust tip
very rich - is a bastard to start when hot, uses a lot of fuel, sooty. Will bog quite easily and does not always clear as fast as it should do.

[Jac-al]

thanks cmsmj1, thatscwhy i made a comment about 2 pennies awhile back. i know what bigger or smaller jets do, what i dont understand is why some people are telling me to go smaller and some bigger from std

[hrc rr]

hey cam quick question, if you push back a slide (89 NC30), should it spring shut almost immediately, or gradually?

Reason I ask is if i install my slide with the diaphragm cover screwed on (diaphragm rubber sealed), it takes a while for it to slide shut. But if i have the cover open just a bit (unsealed with outside air allowed in and out), the slide with snap shut almost immediately when i release it. Carbs have been sitting for a while but i've done my best to clear all passageways with water pressure/degreaser spray and soaked the rubbers in kero as you know.

Is this to say there's a blockage somewhere when the diaphragm cover is sealed and only releasing/sucking air at a slow rate, or the diaphragm is too dry to keep up? Kinda confused since if the diaphragm rubber was the fault i'm guessing it would still shut slowly with and also without the cover being sealed? Slide hole is undrilled and clean.

[CRM]

so whys everybody telling me to put in 118/120's when std was 115/118

As mark has said, a few have no idea and only go on what either worked for them, or on what they have read.
However a few of us have owned and stripped more 30's and 35's than is healthy and kinda know them pretty well.

the default 115/118 is fine with a healthy motor and standard induction and pipe, with a different can / system then rule of thumb would say up one size to compensate - however this can show holes in a lean midrange and other symptoms depending on the pipe

I had a NC30 that was standard and needed a 130/130 setup to run anything like and then it was still not right. turned out to be cam gears pressed onto the cams wrong so all the timing was out yet appeared to be correct.
once cams were replaced the standard jetting worked and made a massive difference to the bike.

Each bike is pretty unique and what works for one might not work for you. your arse is a good dyno, and with each strip / rebuild you get better and know your bike just that little bit better.

[Jac-al]

hi, does anybody know of any thread or how to explain how to do jetting and carb cleaning on a RGV250? I know nothin about 2strokes

[Jac-al]

??

[CMSMJ1]

Carbs are carbs - clean them, make sure they are set to the manufacturers basic specs and go from there.

And you need to go and have a loom around rgv250.com!

[Jac-al]

thanks CMSMJ1