New Engine, Won't Start!

The moment I'd been waiting for never arrive. New 110 engine, all fitted and ready to go but no sign of life. Petrol running through the carb, health looking spark. I've obviously got something wrong, any ideas where to start?

Set the carb to it's standard settings.
Did you use all new gaskets on the carb?
No signs of cracks in the engine?
Check valve clearance and timing.

What brand of engine? What kind of ignition?
New engine with warranty or sold as new on fleabay?

Thanks Waynus
It's a zongshen, Chinese repro, purchased from monkey bike uk, warranty shouldnt be a problem if it's an engine fault. All new gaskets and will give it good look over tonight. I did change fuel pipe for something a bit sleeker, plenty of fuel seems to be running through carb when I tip it over so can't imagine it fuel flow. Will check carb set up, points ect.
Thanks again.
Morris

Zongshen is a pretty good brand. (Chinese-wise speaking)
Unfortunately, there are some repro Zongshens as well.
(replicate the replication?!)
The engine doesn't have points, so no need to check those.
It really sounds as if you got ignition issues. Sure it's a good (timed) spark? You did the 6v-12v conversion yourself or is it an original 12v bike?
You filled the engine with oil, didn't you?

You could try to pour some fuel in the inlet of the cylinder head, and try to kickstart it.

Engine checked for oil, all good. I wondered if I'd flooded it as the plug was wet with fuel but still wouldn't start with a clean. Think I will have a look at the carb again and check for any air being sucked in.
Any way thanks for the pointers, I will update on how it goes later.
Thanks

Just spent another hour going through possible causes. Checked fuel flow, seems ok, checked for air sneaking in around carb all seems ok, dosnt seem as though fuel system is the problem. 12v loom fitted to electrics of new engine so I can't see that is part of the problem.
Not sure what too look at next!

If you have got a wet plug it will not be a carb problem you only get this if it is an ignition problem, couple of questions
is the plug gap correctly set as plugs can get knocked easily also did you try pouring a small amount of fuel into the manifold as even if the timing is incorrect it should still ignite the fuel and you would get a misfire, was the plug supplied with the motor ? and when I had problems of a similar nature I replaced the plug and this cured the problem ?
dont give up it's all part of the ST experience.
Tufty

Thanks Tufty, I will have a look at the plug and check the gap. Waynus also suggested petrol in the manifold, which manifold are we talking here, carb, exhaust?
Don't worry I'll stick with it, keep the advice coming, it's probably something very obvious I've missed.

It's the carb manifold.
Do you still have the original 6v coil fitted?
That could be the problem as well...

She's a runner, at last but still bemused by a couple of things. It only started with a bump start, would not start kicking over, not even a whisper of starting. Bumped it out of desperation and it started and runs fine. Tryed to kick it again and would not have it. Left it for a while and came back and managed to kick it over and start it. Turned it off and then it wouldn't start with a kick again. Maddening, at least it runs though and seems fine.