Looks like I need to replace the timing chain on my Grizzly. I checked the timing and found that it is out probably two teeth on the top sprocket. A few questions:

1. Do I replace just the chain or do I have to replace both sprockets and the chain? I know on a car you always do it in a set. I am just not sure about these machines.
2. Is there a good aftermarket set or do I just go back with Yamaha parts. The chain is about $25 on yamaha parts house. Yamaha #94591-40126-00
3. On the cylinder head cover, I noticed there is not a gasket on it when I took it apart. Didnt see one on the parts break-down either. Surely this is not just metal-to-metal with no gasket. Use RTV when I go back with it? I just dont want it to seep oil down onto the cylinder.

   

4. Anything else I need to be replacing while I have this broken down?

Thanks,
Kirk