120/120 jetting?

[AdrenalineJunky]

Hi everyone,

I've been working on the carbs on my NC30 that I bought a couple of years ago but haven't used in almost ten months.
The exhaust on this bike has a removable baffle with the "road legal kitemark" stamped on it, so it is either "quite free-flowing" (baffle in) or "extremely free-flowing" (baffle out). I hadn't opened the airbox or carbs before, so I was surprised to discover that the previous owner (who only used it for trackdays) had the following setup:

Standard air filter
No sub air filter fitted
Slide holes drilled out to 3.05mm
~1.5mm washers on the needles
120 main jets in the front and the rear carbs

Despite all this weirdness, the bike used to run pretty well - I got over 50mpg(!) all the time and decent riding experience, also tested top speed at slightly more than 130mph on the speedo.

I also did the valve clearances and found that a lot of them were out of tolerance (all of which were too tight; obviously nobody bothered to check it, bike's on +30,000 miles now) and the number 4 cylinder had a Denso sparkplug where all the rest were NGK. Now I am putting it back together with all NGK plugs and correct valve clearances.

I'd like to hear from those in the know about the airbox/carbs, about whether I'd be better off to reset everything to the recommended settings. That is, should I:

(1) put the main jets to 118/120 or maybe 120/122,
(2) put the 1mm needle washers instead of the 1.5mm,
(3) put the sub air filter in.

Also if anybody knows anything about the 120/120 jetting setup - is this likely to be something that people have used for a reason, or is it just some random decision by a previous owner? I don't actually know why the front and rear jets should be different sizes, but all the setups I've read about say slightly smaller in the front than the rear.

[AdrenalineJunky]

should have mentioned, despite the high MPG and decent performance, the bike idled really badly and would often cut out. But I dunno if that was more likely to be a carb//air problem or was due to the sparkplug being different in one cylinder (also with way too large a gap on that plug), or maybe to do with the valve clearances being so out of tolerance.