When you sit on the bike, you'll hear it on the right side of the engine.

 

sounds like the CCT. The OEM ones are a common failure. You can pick up a manual one for pretty cheap, APE makes a nice one for about $60 there are also a bunch of threads on this topic too.

 

It kind of sounds like valves, but I am sure that it must have been there before you did your service work.
With the way your engine sounds, you really need to check and adjust as needed.
Be sure you feel confident in doing this or get help from someone you trust.
I bought an ATV with no compression and found out that someone over adjusted the intake valves, causing them not to seat. I was lucky that the valve never burned up!

GOOD LUCK

PS > Does anyone ever run LUCUS in their engines?