st70 carburettor settings

need some advice on the 3 adjusters on the carburettor. there are 3 adjusters are there specific settings on these or you just adjust as you go

Starting point before fine-tuning the carb on a healthy stock 70cc engine and carb.
- maker sure all rubbers, washers are in place and in good shape!
- gass needle: clip in middle position
- air screw: close, open 1,5 - 2 turns.
- idle screw: (screw with spring) open up untill the engine is idling steady

I have tried a few positions on the three adjustments but just can't get it to fire as many years sitting.
I am having to hot wire it as there is no ignition barrel and key with brown connected to black.
I have checked the spark plug with it out and theres a good spark even tried with full throttle but won't start any advice?

Try to kickstart in a dark room, check for sparks under the flywheel
Check the ignition timing (F) and cam shaft timing (T)
Also, check the points for wear.

got it started and running but breathing oil from broken exhaust stud
whats this mean?

Sure this is oil and not regular exhaust gasses?
Worn piston rings, cylinder or valve gaskets.

definitely oil
what needs to be changed on the engine to rectify

I'm afraid you'll need to take the top engine apart and visually check all parts and gaskets on both condition and correct placement.

Do I have to remove both engine block or just the front one?
I have seen a guy selleng one on ebay for £40
http://www.ebay.co.uk/itm/Honda-Cylinde ... 19eb96023d

Yeas, start with the cylinder head.
You also might need to check / change the piston / cylinder.
The bottom engine should be fine.

From what I read in the ad, it's possibly a cylinder head for a OT50 or NT70, not for a 6v 70cc engine (OT70)