Think I may need a new head :(

[Detonation]

So the bike won't start at all, not even an attempt.

I have spark.

I seem to have fuel as the fuel in the fuel pot I'm using is going down.

Motor turns over easily on the button.

Once it stops raining I'm going to pull my carbs, clean them and have a quick look down the intake boots aswell

I move in 2 weeks so I can't afford to pull the head off have a look order one then try and get it back together in that time.

Any other ideas of what my problem could be?

I'm trying to track down a pressure tester ATM through friends.

There's a really TINY, TINY, TINY tapping noise from the top of the head as its turning over