Hey there,
Allow myself to introduce, err, myself. Just signed up here, lots of useful info, which I've been sifting through, cheers.
I bought a track project 89 NC30 recently, wasn't running, had been sitting around for a few years by the looks. Pretty much stock as a rock, and in quite good condition. Anyway,I've taken the carbs off, had a look inside, and put the mixed up bits back in their correct positions. ie. needles were in reverse order, emulsions tubes the same. Thankfully the bowls and slides were spotless and in good nick. However, the main jets are all 122s, which if i understand correctly is probably too big for stock airbox/exhaust? I put everything back on and it started up straight away and it runs with the throttle opened a bit, but blows a fair bit of smoke and won't idle (just bogs down and dies.) Seems to rev fine, but still with the smoke. Would the jet sizes account for the smokyness?
The other issue I have is that the throttle cable is too tight. even with the adjusters at maximum slack, the throttle is pulled open when the bars are turned to the right. Any ideas?
Much obliged if anyone has any suggestions.

Is it blue smoke?
If so and if you're lucky someone put some oil down the bores before leaving it standing.
The rings may also be gummed up and it might settle down after a while.

In life a pessimist,
With bikes an optimist!

Stupid question but have you turned the idle adjuser up?

You can set it too low too idle.

if it holds an idle at 2500rpm or so then wont idle any lower( gradully back the idle screw out until it dies) you probblay have blocked pilot circuits in the carbs (common from long term storage) and / or air leaks on the carbs.

Idelaly you want to get it to be able to idle at some sort, check your coolants not leaking when its upto temperature and your oils all ok (ideally change oil and petrol and maybe coolant if it looks minging if not for now at least it should be fine, just make sure its filled up)

take it for a gentle ride to work everything but not over-stress it.

this will burn off any crap from the engine, if its still blowing smoke after a decent run then investiage further.

thanks for replys. to clarify, I have played with the idle adjuster, in fact when it first started on choke it shot up to 3K revs as it was set high. I can bring it back to a more reasonable idle on choke, but after running for a couple of minutes and taking choke off it still bogs down. All the carb jets were cleaned/checked. air leak is a possibility - the carb rubbers were very hard and carbs took forever to ram back on the engine block. not looking forward to that again.
On further inspection it also seems the oil level is too high - i hadn't changed the oil as it appeared clean, but I'll go through an oil/filter change and coolant flush too. Spark plugs seem a bit blackish (though otherwise appear new). have ordered some 118/115 jets.
I'll try put up a youtube clip of it to show it better. Really hoping the engine doesn't need overhaul.

Hi there, when starting from cold with full throttle (as you should!) the engine should rev at 3000-3500 revs, so yours sounds normal in that regard. Leave it idling with full choke for perhaps 3 minutes, then try turning off the choke and seeing if it idles.

It sounds as though the throttle cable is getting moved by the lower yoke on the forks. The cable route is displayed in the workshop manual, info and download in this thread: viewtopic.php?t=28460

The main jets only come into play above 8000 revs or so, they won't be an issue with what you're trying to resolve.

These engines are very reliable, I wouldn't be concerned unless it's blowing a lot of blue smoke! It's probably just condensation evaporating and crud build up burning from the engine.

ok so i hooked up a new battery, changed the oil and filter, fired it up again and the plot thickens...
I took some video to try and show the smoking/idle fluctuations, but also something else came up, fuel started dribbling from somewhere as you can see on the video. https://www.dropbox.com/sh/vaqk9jhphxjy ... HsBCLCgiSa
This didn't happen before, however before i ran it on the sidestand with old fluids/battery; this time upright.
I traced the leak to the carb overflow hose and it seems the two rear carbs are at fault. Damn it, i thought i had the carbs more or less in order. somethings obviously still blocked, what usually causes this? (At least I'm less concerned about the engine internals now - the smoke seems to have cleared up).
Thanks again

Katoom wrote:ok so i hooked up a new battery, changed the oil and filter, fired it up again and the plot thickens...
I took some video to try and show the smoking/idle fluctuations, but also something else came up, fuel started dribbling from somewhere as you can see on the video. https://www.dropbox.com/sh/vaqk9jhphxjy ... HsBCLCgiSa
This didn't happen before, however before i ran it on the sidestand with old fluids/battery; this time upright.
I traced the leak to the carb overflow hose and it seems the two rear carbs are at fault. Damn it, i thought i had the carbs more or less in order. somethings obviously still blocked, what usually causes this? (At least I'm less concerned about the engine internals now - the smoke seems to have cleared up).
Thanks again

Either your floats are set wrong (did you set float heights) or the float pins are not sealing.

This will cause fuel to overflow and bike to run like shit.

Good then.
Off with the carbs we go again.

so the carbs came off again, i can't see any obvious problems with the float valves/heights. all parts look in good condition and seem to be sealing when I blow in the fuel line. The rubber connecting boots look reasonably farked though, along with the float bowl gaskets so have ordered new sets of these. would an air leak cause carbs to overflow at all??

Katoom wrote:so the carbs came off again, i can't see any obvious problems with the float valves/heights. all parts look in good condition and seem to be sealing when I blow in the fuel line. The rubber connecting boots look reasonably farked though, along with the float bowl gaskets so have ordered new sets of these. would an air leak cause carbs to overflow at all??

no.

How did you measure the float heights?

And if you turned the idle adjuster down when your bike was idling at 3k with the choke on the idle adjuster will be too low now.