take the spark plugs out, and crank it over, wait till you can smell fuel in the bores, then put plugs back in, and crank it over, See if it starts then.

i recon you got an air lock in your fuel line, if you change a mettering unit or like i did, took mine of to clean it out etc. You will 99% of the time have air in the fuel lines. The way above will let the air be pushed out of the hole where the plug normaly is.

give it a go, if you haven`t already that is.