Topic: Engine Sound?

[Vintageguy]

Ever since I bought my 1978 CB750 F (May of this year) it has made a noise in the lower, front-center engine area. Not a banging. Not a knocking. Not a ticking. It's not the clutch. The best I can describe it would be a "mechanical motion" noise. Sort of like friction, but no squealing or grinding. Just a sort of non-descript "hushing" noise, like something metal moving. The bike has good power and does not exhibit any other issues I'm aware of in terms of the engine. Starts easily and runs strong. My first "quiet" bike in many years so maybe they all do it. Any thoughts?
Thanks to any and all. 

[beemerbum]

Perhaps a cam chain tensioner adjustment could help

[BobbyR]

If you pull in the clutch handle and it goes silent it is the usual clutch rattle. If the carbs are out of synch you will get a cam chain noise which usually goes away if you increase the idle.

[alacrity]

That's like turning up the radio in a car that is out of tune because it's making bad noises.  Better to synch the carbs to quiet the symptom (and enjoy the added benefit of riding around with your carbs in synch -- performance, ride ability, throttle response, mileage...). Or put in ear plugs and turn up the idle.  haha. that's certainly easier.

If you pull in the clutch handle and it goes silent it is the usual clutch rattle. If the carbs are out of synch you will get a cam chain noise which usually goes away if you increase the idle.

[PeWe]

My CB750 K2 get a high pitch singing sound on 5th gear and 4000 rpm only. Gearing 17:48.

I think it is the cooling fins on cylinder or head vibrating. The reason of the rubber dampers between cooling fins. Head and cylinder older, K1.

My K6 got bad squeeling sound around 4600- 5100 rpm on 5:th gear. I first thought it was cam without oil due to blocked oil passage. Found when searching on the rpm range and inline fours, this rpm range is the resonance frequency of the engine. Bad sound could be exhaust not really tightened. Found ex spigot cyl3 was loose tightened it and OK.