Hello everybody, this is my first post (I think I'm posting this in the right spot) I need some help. I recently rebuilt the engine to a CBR600F2 approximately 3 months ago (my first time ever doing something like this by myself. I'm not the smartest when it comes to motorcycles as I'm still very new to the mechanics side of it). At the time of me posting this it just cranks and cranks and does not fire. Yesterday I sprayed starting fluid in the carbs and it backfired twice (that's it). It's not getting spark and I don't know why. To my knowledge I have everything hooked up and hooked up properly, CDI Box is good and the Voltage Regulator is good, the Battery is charged and I replaced the ignition coils, everything is grounded correctly. I'm stumped, my instructor is stumped (he doesn't really know anything about bikes to begin with). If anyone knows anything, any suggestions and help will be greatly appreciated, because I want to get this (at this point) started and being able to ride before I graduate.

Thank You All

(FIXED THE ISSUE, THANK YOU TO ALL FOR THE HELP)

However I have encountered something else, under the headers, there are these two holes under the headers. (4 total), I don’t know what they are for, and I don’t know how to go about closing them up (cant find anything online). Can anyone help me. (These holes were not on the last engine head that I had on this bike)

 

From the backfire, try swapping the connectors to the coils. ISTR that the two connectors are identical and getting them the wrong way round would mean that you’re firing at bottom dead centre rather than TDC.

 

They're hooked up correctly and it's still not starting. (Crank No Fire)

 

If you are not getting a spark and coils etc are all hooked up correctly then it would point to the ECU, how do you know that it is good?
Follow the steps at point 2 below to identify the problem: