[maviczap]

Can't see how changing the cct's is going to cause your issue, unless the chain has jumped and the timing is out, but as there are no rattles. Think if you'd got it wrong, then there would have been a big bang.
However you could check the compression on both cylinders to see if there is a loss, which might mean the timing was out and the valves had touched the piston and bent them, but if expect the engine to be noisy.

Perhaps when removing the plugs you've disturbed the plug lead and it's not sparking properly, our you've not seated the plug cap properly or not got the plug in tight?

Have you disturbed the airbox when lifting the tank to get to the rear plug?

Have you trapped the fuel line or not attached the vacuum line to the tap properly?