Kohler CH23 Low oil pressure on right cylinder head

Hello,
I have a Kohler CH23 with low oil pressure on the right cylinder head, the other side is great oil goes everywhere but for some reason the right is very low. any ideas where the obstruction could be located? 
This engine is on a Lexmark mower that the DOT owned, so I am not sure about the history although it appears to has sat unused for a while, so I am planning on running Liqui Moly 2037 Pro-Line Engine Flush through it this weekend to see if it isjust gunked up. 
 
any suggestion would be great. 

Hello,
The valve cover on the right side was damaged when I got the mower, so I removed the valve cover to repair it and noted the rocker arm was way too clean and not much oil present. I started the engine and had very little oil spraying out of the right head. I want to compare the volume against the other side, with the engine still running I started to remove the left side valve cover and a good amount of oil started coming out as soon as started loosening the bolts.