Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
Because a cylinder head exchange requires removing and installing the cams, re-installation can be a problem. The first thing I would suggest is doing a compression test. An internal combustion engine only requires 3 elements to run, and you said you have 2 of them, spark and fuel. The only other element needed is compression. Run a compression test on all 4 cylinders, with all spark plugs removed during the 4 tests. Let me know what you come up with.