Engine knocking noise

Hi, I finally started my VF1000F2 to my delight after it sitting in my garage for the last 7 years, Upon it starting and running I heard a knocking noise coming from the front cylinders and then turned off the ignition. Will add, before I laid the bike up, the engine was running sweetly. All I have done during its long lay up has been to remove and refurbish the front exhaust pipes and balancing box (and replace studs), and change the oil and filter. I was careful when refitting the front exhaust downpipes not to overtighten the studs and did think it may an exhaust leak but quickly dismissed that. Now thinking the worst with it being a stuck valve perhaps and hence causing engine damage! . Now considering taking the top radiator and cooling fans etc off to get the front rocker cover off to start investigating. Any thoughts or comments would be welcome. Not a good day!

Sounds like a blow from one of the exhaust ports.
I’ve had this happen when replacing the exhaust.
It sounds horrendous but on one occasion it just needed tightened up,worth checking before pulling the engine apart

Thank you for your response and I believe you are absolutely correct as to what the noise could be, as after writing the above I did start the engine again and detected the exhaust leaking from the right hand side exhaust port (where the noise was) but wasn’t convinced on Friday it could make such a noise. I did go ahead on Saturday and remove the radiators, exhaust and rocker cover to check the valves and their clearance, and all was well. I will now reassemble and try to make sure I get a good seal at the exhaust port and fingers crossed. I’m always conscious of not over tightening the nuts on the exhaust studs! Will provide an update when done.