How can I adjust the valves on my atv? It starts hard and blows out oil when going top speed.

 

They are easy to adjust by removing the valve cover and use a feeler gage to get the correct clearance. Now...that is not what is causing your engine to blow oil out at top speed or causing the hard starting. You have other issues with your engine. I would highly recommend picking up the factory service manual for that machine and start trouble shooting.

 

You will require a manual....too much typing to try to explain. Here's a link for you. Only $5....will pay for itself in just a few minutes of work.
https://www.tradebit.com/G/manuals/14-atv