2003 Polaris Sportsman 400 Oil pump will not prime

[Brian Sosebee]

I just rebuilt my 03 sportsman 400. Put everything back together added oil per the manual. Pinched off the oil tank vent line 2" away ran for 45 seconds then cut it off. Check oil level and it was still way high so I wasn't confident that it primed so I did it again. Checked again and it's the same. Remove the oil filter and it is dry. I did the procedure again and the same results.

I'm worried to keep trying this as the only oil in the engine is what I used to lubricate the parts when reassembling the piston. The crankcase was drained as well.
I Removed the oil tank and checked all the lines for obstructions and the screen filter and the vent hose and everything is clear. I even pulled a small vacuum on the oil tank while it was pulled off to make sure there were no leaks. The dipstick cap was on tight so I'm not sure why this thing is not priming.

Anyone have any suggestions. I thought about pre-priming the oil lines from the oil tank to the crankcase to hopefully help the system prime. I'd like to be able to add some oil to the crankcase to so I wouldn't feel so bad about running the engine for another 60 seconds without oil. I dropped just a little bit of oil in the spark plug hole to help condition the sleeve right now.

What do I do? Anyone had or heard of an oil pump failure on these. Btw oil pump is working fine before I did the top-end rebuild and the oil pump was not touched.

Please help!!! Thanks all for any and all help.

[gillies_robert]

only oil pump failure ive seen is the counterbalance gear coming loose on the shaft. my own personal sportsman 500 has done that. what does your relief or check valve in the crank case look like?