Hey folks, I'm having an issue with my Sportsman 500, non-h.o. I think I know what it is, but before I spend a bunch of money to fix it, I thought I would ask the experts to see if there was something I'm missing.

The main issue is that I'm not getting any oil flow. I did some work on the upper end - camshaft, rocker arms, and timing chain replacement. While doing this, I completely drained the oil including cleaning the screen in the oil tank. After re-assembly, I could not get the oil pump to prime. I have tried the priming procedure repeatedly, maybe 20 times, without any success. I started to troubleshoot the issue, I've:
- dissembled the oil tank to check for blockages
- replaced the oil check valve, which actually did have a chunk missing out of it
- blown out all oil lines I can access with compressed air - all of my lines are clear
- completely drained and re-filled the oil
- added oil directly to the engine through the oil filter inlet and I'm still not getting any oil out
I'm out of ideas here. I'm thinking the oil pump is shot. This could explain why I had to replace the timing chain in the first place. If I wasn't pumping oil up top, it could have stressed the old chain enough to break. Anyways, do any of you see anything I'm missing? Is there a way to test or diagnose the oil pump without complete removal?

Thanks for the help!