Re: Engine noise and idle trouble
Idling can be affected and tuned up by eliminating any possible air leaks (check for them first) and proper jetting/ slide needle/ slide height settings.
Also if you have a CNSv2 carburetor, the "choke" plunger can be messing with you.
Some do not seal closed all the way when the "choke" is turned off.
There is no perfect "this will work for you" settings as no 2 engines are identical.
It also could be a bad spark plug.
If we are discussing an HT 2-stroke then......
The whirring is most likely the sound of the gears meshing together.
Some engines are louder than others.
It could also be the flower nut locking screw or clutch fingers digging into the inside of the clutch cover. Take the cover off and have a look.
As TBN said, try adding a teeny bit of grease to the gears, a blob about the size of a pea, right where the 2 gears mesh. Do not worry about spreading the grease around all of the gear teeth, they will do that automatically when they are spinning.
Caution! Too much grease will only make a mess of the inside of the gear case and possibly contaminate the clutch pads and friction surfaces.
Remember these engines are not knows for stellar quality control and precision fitting parts.
They are cheap, they run well (usually) and they are cheap to buy major replacement parts and tinker/ modify with.
"It's a chinagirl. It's a sometimes fun little engine that often will break your heart. It's disposable.
Does not come with a fortune cookie."