Correct mixture ???

After racking up about 50 miles,running on a new plug,i decided to check the condition and found it to be jet black,should it be light brown???
Been jet black does this mean its running to lean? or to rich?
i know were the mixture screw is on the carb,but which way shall i turn it? and by how much? is just trial and error?

Thanks guys in anticpation of answers..........

Too rich or could be oil fouled .Adjusting screw only affects up to app.1/4 throttle opening, lower needle in slide to lean off at larger throttle openings.To do a proper plug check run at full throttle for at least 30 secs.(longer if poss.)at or near top speed, switch off ignition and kill engine at speed and then look at plug-mid/dark brown is ideal.
Chief

Thanks Chief,but i,m confused, sorry i am no expert in laymans terms are you saying that adjusting the mixture screw wont work? do i have to dismantle the carb? and what does oil fouled mean (something else wrong)???

A plug could be black if your engine burns oil,ie if rings/bore exessively worn or valves/guides seal worn and allowing oil to drain or be sucked into combustion chamber.as a guide oil burns as blue smoke and exessive fuel black from exhaust.If your engines in good shape and not high miles it shoulnt be oil fouled.
Make sure you have correct plug fitted and do plug check as suggested.(engine fully warm)
Adjusting pilot screw wont make much difference really(only at and just above tickover)
To adjust needle height remove slide from carb,disconnect throttle cable,remove needle and raise circlip one groove if you wish to weaken mixture(if memory serves there are 5 grooves and std position is middle)
If your not confident to do these things find someone who is,severe damage can be caused by working an engine hard on a lean mixture!
Chief

Well explained, chief.

A small addition:
0/4 - 0/4 throttle = idle jet + screw
0/4 - 1/4 throttle = mixture screw
1/4 - 3/4 throttle = needle height setting
3/4 - 4/4 throttle = main jet
0/4 - 4/4 throttle = air leaks, dirt, mechanical faults

Cheers guys...... should not be serious as the bike has only done 2000 miles .

Spot on waynus,minimal typing too!!!!
A couple of other points too Arny-obviously make sure your airflow thru air filter isn't restricted.
If someone has been a bit rough handling the float and increased the fuel level in carb that would also lead to a richer mixture and check jets are fully home and seated.
Dont just use plug colour to diagnose a problem,thats really just one indicator,if there is a problem you should have other
symptoms -excessive fuel consumption,poor performance etc etc.
Chief

You no what chief,you have just struck a bell !! recently i had to dismantle the carb as the float was sticking and fuel was leaking after the engine was off. i did clean the jets and the float had a lot of scale which i cleaned off, i may have been a bit heavy handed !!?? and maybe accidently adusted the float Bugger do i have to dismantle the carb again or could i raise the needle as you have described above ?
Arny.

Set the float Arny,the fuel level needs to be correct before you would make any adjustments elsewhere.
I'm not sure if a figure has been given for the exact float height (Waynus ?)but if you look carefully at it,make sure it is symetrical with parallel angles etc and basicaly looks 'true and right' View it whilst holding the carb body and letting the float hang down (pivot uppermost) with the tang just in very light contact with the valve.
Measurement is usually taken in this position from carb body (were the float bowl seats) to nearest(upper) of float.
To make an adjustment in the fuel level you very carefully bend the tang and then re-check float position.
Only very small adjustment at the tang will change level significantly.
Nearer float is to body(higher) the richer she'll run.
Chief

Cheers my friend,i shall give it a go..............