Hi
Have a look at the fuel first. Are you using fresh fuel?
Check and make sure all four carbs are getting fuel. If not check for blockages, kinks etc in the fuel line. Next have a look at the fuel tap it might simply be blocked.
When you are happy the bike is getting fuel check for sparks. Make sure each plug is the correct grade and is gapped correctly. Also check to see each plug gives a nice fat spark.
If the bike has got fuel and sparks and it still won't start then you will have to dig a little deeper. Hopefully the above will get it going.
Good luck
Grizzly
