CB750F 1981 Engine noise mystery knocking? need to synch carbs? serious trouble? скачать в хорошем качестве

CB750F 1981 Engine noise mystery knocking? need to synch carbs? serious trouble?

Noise disappeared when starter gear freewheel bolts were tightened, please see my other video for more details. My cb750 from 1981 has a loud rythmical knocking at idle and up to about 2-3000 RPM. it runs well and no noise can be heard at higher RPMs or under load. I have thought it to be cam chain rattle and tried to adjust the cam chain tensioners, both drive chain and connector chain, without any change in the noise. The knocking or clanking is not heard, at least not as loudly when the ignition is killed while rolling at speed and with the enginge being pulled around up to 3000RPMs. - Could this mean that the noise comes from misignition or detonation? I have little prior experience but have tried to listen to other videos to get a reference to be able to diagnose the noise. I have tried to listen with a screw driver, but have not been able to say with certainty where the noise is coming from. I have also suspected misfiring cylinder, especially since #2 exhaust is always markedly cooler than the others. I just recently found and fixed a vacuum leak from #2 Carb by plugging the vacuum nipple that had been left open. Could this vacuum leak have caused permanent damage leading to the noise? Could it be carbs in need of synch? Or could a dirty and gummed up carb lead to misfire with this sound as a result? Or am I in serious trouble? Crankshaft failure? something else? Please, if anyone has the ability to hear what the cause of this noise is, or have any further info questions about clarifications etc. Please help!