On a atv.what oul shoyld I use if theres a knocking noise starting?

The knock is either piston slap or a failing bearing. There is no special oil or magic fluid that will repair this. It is not going to fix itself, it is only going to get worse.

Continue to ride in this condition and you risk catastrophic engine failure. Right now, the condition is repairable. Wait until the engine fails and you may end up with a worthless pile of junk.

Personally, I would not ride this until it has been looked at by a reputable professional mechanic.

Knocking at idle andit sounds like the top end. The first thing I'd check is the cam chain tensioner. I'd assume it has an automatic tensioner, but that doesn't mean it's doing its job. Some of the old Kaw tensioners on the 6 cylinder engines were famous for letting the chain get loose, jump a tooth and then pistons would hit valves. Also make sure the idle is high enough. You should do a pressure test on the oiling system. On my old KZ1000 the oil pressure light started coming on at idle at around 35,000 miles. I had to remove the oil pump and lap the body to tighten up the clearance and that took care of the problem for the next 80,000 miles. In short, there's a number of things it could be and you need to do some serious troubleshooting before you continue using it OR start buying parts. Could be something really simple or really serious.

you cannot go a heavy viscocity in ectreme cold if you have a bearing knock you need to fix it before it gets any worse. The oil may be too heavy now when its cold what do you have in it now? and go check with the shop I would take the vehicle in for service just to be on the save side. engines are expensive.

Has it had maintenance at any time? Maybe it's valve noise. Read the manual and find out how often it says the valves need to be adjusted, or take it to the dealer for a check.

There isn't any oil that solves incorrect metal on metal contact.

Ride it really hard that will make that noise stop