newbie seeking advice

[chappers]

hi all... im a newbie on a mission!

first off let me start by saying that my name is karl and the virtual bar is now open!

to cut a long story short, i bought a half-project...half-running nc30 off of the dreaded ebay, and need abit of advice in getting it running right.
i have not ridden the bike yet as i am trying to get it to run propperly first, so you will have to excuse my retardedness..if it just needs a clearout!!
when running, the bike sounds fine and isn't missing or anything like that, but when you open the throttle, it revs sweetly up to 6k revs..then it sounds like its strugling to rev..almost like its starved of fuel(abit like when carb icing takes affect) then once it gets to 8k it clears and revs nicely the rest of the way up the rev range.

i have took the carbs off, and the inlet rubbers look ok, i have cleaned all the jets out and put frest petrol in it.

the bike has a scorpion straight through can..and the jets that are on the bike are 118's on all of the carbs
obviously im going to change the oil, fiklter,air filter and new plugs with the correct gaps..so basically a service!

but i think it is abit weird how the problem is only through 2k of the rev range.
i dont know exactly what carb ballancing is but i could shore do with some advice if it is that.

the last time the bike was taxed was 08/2006...so it has been stood a fair amount of time.

please help me!!
oh... and the bike is an import 1989 model (nc30)

[CMSMJ1]

Welcome to the site chappers.. we'll sort you out!

first thing - is this revving problem when under load or in neutral?

Also, what airbox have you got on it? Is it standard and looks unmolested?

What filter? A paper one? Foam?
Get some pics up too and fill us on a touch more on the situation where you agve this missing.

When you cleaned the carbs were they scabby? Should be no major stress to sort it.

[chappers]

carbs werent scabby...suprising clean, but there was some old waxy petrol dried to the inside of the bowl.(brown)
that all cleaned up nicely.
air filter needs replacing as it iis showing signs of age and is quite dirty.. but it is a standard honda paper item. the airbox itself is not modified.

problem is in neautral. however i havent ridden the bike yet as i have been busy at work..and stripping the bike.
will add pics in a little while as ive gotta take me lad out to get some ingrediants to make a cake!

[chappers]

ok...i forgot to mention that the bike has had a different engine put in it, at some time in its life..would this make a difference if it is from a different year?? and how can i tell what year is it?
bike also has mph clocks which must have been added afterwards..as it is a 89 model.

to be honest its abit of a dog at the mo..but once we get it running right..i can sort that out

[chappers]

just been out and investigated...engine is from a grey-1990/91 model

[Cammo]

bike also has mph clocks which must have been added afterwards..as it is a 89 model.

Yours also has later model forks. The engines weren't changed between nc30 models, but the carb jetting was. Later model carbs had 115f/118r jets in them.

Did you completely clean the carbs? Blocked pilot jets could be responsible for your symptoms, if the carbs were (very badly!) out of balance they might also contribute. You can balance the carbs pretty well without vacuum guages by following the haynes sequence.

These bikes often have charging problems, good idea to check what votage the battery is seeing at different revs. The standrad reg/rec is crap, change it for a yamaha or good aftermarket one if it hasn't already been.

Like CMSMJ1 hinted at also, airbox mods can cause running problems like yours, check on parts diagram that you have all parts there:
http://www.akhara.com/nc30/index.html" onclick="window.open(this.href);return false;

These bikes are bulletproof really and totally rebuildable, once your problems are sorted it'll go forever. Get youself a haynes manual if you don't already have one, it's invaluable for doing this sort of stuff.

[Cammo]

and more...

it revs sweetly up to 6k revs..then it sounds like its strugling to rev..almost like its starved of fuel(abit like when carb icing takes affect) then once it gets to 8k it clears and revs nicely the rest of the way up the rev range.

If the problem is fuel/carb related, these revs would probably point at needle issues:

Check that the right needles are in each carb (they're marked): J51A in the rear, J51B in the front.

Check that the float height is set to 6.8mm.

Check that the emulsion tubes (that the main jet screws into) are in the right carbs: 5-hole in rear, 4-hole in front.

Check that each carb needle has a 0.5mm washer underneath it.

Check that all 4 pilot screws are set to 2.25 turns out from fully in.


These are all standard settings (excpet the pilot screws but it'll suit your pipe), you'll be amazed at how much an owner before you has stuffed these around!

[chappers]

cheers boyo's ^^^^^ i will take a propper look at the carbs tommorow. got to the rear plugs today and they were a little sooty and wet with fuel..so im guessing that they are being over-fed fuel.but will take the carbs off tommorow and get them all out and take a propper looksy!

as for cleaning the carbs.. i took the flowt bowls off..removed both jets in each carb and blew them out...so i could see clear daylight through all the holes.

with the carb settings mentioned above....would those be fine with the race exhaust?

[chappers]

update pt 3!!

finally got the carbs off and took a propper look around them. i checked all the specs as given above( thanks fella ) and everything was as above apart from the mixture screw was further out. i also took the plugs out, which looked abit wet but fine. i did gap them correctly as they rewe a little off.
the strip down didnt really make a difference.. but i did give it a quick hammer around the block and the problem its self isn't that bad. you cant notice it on propper riding.the only time i did notice was when i went in to second and i tried pulling away and it took a second to clear itself at 8k revs.
it to me seems as though at a tickover and start-up it floods itself..but when on the move it uses the right fuel. almost like the idle jet is too big.
all in all...you can ride around the problems.

so a big thank you to you guys...i can now (after my wedding) enjoy the rest of summer!

[ibby4585]

hi, i am new to this biking lark and just bought a 91 nc30 and i am having exactly the same problems!! did you ever sought it or find out what was wrong??

Thanks
Kris