I just got this atv and I had to replace a rocker arm so I bought a new head for it. When I try to start it it made a humming noise so I turned the engine back a little ways then try to start it and it tryed to start but stoped in the same spot so can anyone help with what is wrong with it.

 

It may just be a flat battery, but be sure, certain, positive, you got the valve timing right, as it could be a valve hitting the piston if you got the timing well out, this would bend the valve, so another strip down would be needed.

 

so then I probably have to adjust the rocker arms

 

No, not valve clearance valve timing.

 

how do I do that one

 

Sorry to be blunt, but if you have had the head off and don't know this throws valve timing out, give up and take the bike to someone who knows what they are doing. If you must do it yourself, get the workshop manual and follow the instructions in that on how to remove and re-fit the head.

 

Everyone makes mistakes when you first start out on this stuff. Don't let it detour you. I don't call these things mistakes anymore, they are tuition. Get the manual and carry on.
I haven't worked on Grizzly but they will be like any other engine with timing marks to line up and away you go. Take your time and I would also check to make sure you don't have a bent valve.

Fixitup

 

I will do it my self because if I do it I will learn and the next one i will be able to do if I take it to someone that knows what they are doing they are going to charge me a bunch and I will always have to take it to them but thanks for you help