In a word...NO!
Some guys get all anal about changing oil on the older machines. Those engines are a "dry sump" meaning the oil isn't stored in the crankcase. It is in the oil tank behind the left front wheel. There is a small galley in the bottom of the case that holds about 1/2 cup (approx. 4 oz.) of oil and a little plug on the front of the engine to drain it. The manual also speaks of removing the bottom oil line on the tank to clean the screen there. Total waste of time as there's never anything in it and you will often have a leak there afterwards!
When you do all that then you're supposed to pinch the line, hold your breath, scratch your butt and start the engine, release the pinch and listen for the whoosh of oil being picked up by the pump.
Forget all that foolishness!
You simply drain the oil tank and change the filter while it drains. Then you put the plug back in the tank and pour in two quarts of oil and go riding...easy peezy!

 

I have changed oil in hundreds of Polaris's and have never done the vent line pinch and never had a problem - if the engine was a fresh rebuild it might be necessary if the oil pump was not primed during assembly, but I always prime an oil pump during installation and all parts are lubed prior to start up - I start the engine and loosen the pressure check plug - if oil pumps out around the threads of the check plug, I tighten the plug and forget it. I have never had an oil related failure on either new or used engines

 

In the manual is taught you must pinch the line when changing oil, but ONLY if you remove the bottom oil screen, which I suppose can create an air lock that will starve the oil pump on startup.

Here is the relevant article from Polaris

https://www.manualslib.com/manual/131457/Polaris-Sportsman-500-Ho.html?page=76

MAINTENANCE Oil and Filter Change Oil Pump Priming

This priming procedure must be performed whenever the oil hose connection between the oil tank and pump inlet has been disconnected.

1. Clamp or pinch off the vent line approximately 2" (5 cm) from the oil tank, between the end of the oil tank vent fitting and the vent line's pressure relief slit.

2. Start the engine. Allow it to idle for 10-20 seconds.

3. Remove the vent line clamp. If the line is bled properly, you should hear a rush of air, indicating that the line is properly primed and ready for operation.Tip: If you do not hear air, the line has not bled. Repeat the priming procedure.

 

Agreed on it being unnecessary if you don't remove and clan screen. I did it once on my scrambler 500 the first time I changed the oil (2005) and removed the screen. There was nothing on the screen at all and the engine is so loud that I don't think it was possible to hear air rushing in in the first place. From there on out I didn't bother with removing the screen and or pinching the vent line and had zero problems in the following 11 years of ownership (sold in 2016).

my 2 pennies

-j-rod

 

How often do you guys remove the lower metal screen in the remote oil tank to check for gunk and blockage?

I plan to do it when I change the oil, since I have never changed the oil myself, and who knows what is in there.

And it's another reason I added the oil pressure gauge, I want to see oil pump pumping oil after I do that. Some forums, I read they dont hear that air whoosh, some do hear it. Someone said he ruined his engine by not doing it after oil change and cleaning out the screen.

Other thing is draining the main crankcase, manual says it holds a cup of oil. I am not sure with the plow base bolted on to the frame (I am left with a short square hole to reach in there) I can actually remove that plug anymore. How about just not draining it and only draining the remote tank, check the oil screen and change the filter?

I figure the oil is getting flushed all around all parts of the motor, its not like that cup of oil is stagnating in there.

 

I've got the manuals and 40 years experience working on engines - the only time I remove the inlet filter from the oil tank is when I am working on something that has had a catastrophic engine failure (cam galled, broken piston, lower end rod bearing failure or worse) or a damaged oil tank that is being replaced. I still have not performed the vent line pinch as instructed.

I view it the same as the direction of rotation arrow on tires - it's a release of liability issue for the manufacturer. With tires, the direction of rotation has no bearing on traction, tread wear or balance. It all has to do with the lap of the ends of the tread rubber as the tire is constructed. A rear tire can be used on the front and a front tire can be used on the rear - just reverse the direction of rotation, similar to some tires that have two arrows one for front use and one for rear use. If you run the tire with the arrow in the wrong direction, you will likely never know even when the tire is worn down to the cord body.

But, if you have the engine under the hood and an oil tank in the trunk (similar to a NASCAR racing vehicle), to assure oil getting from the oil tank to the oil pump on initial start up, you pressurize the oil tank to push oil from the tank through the feed line to the engine.

The Polaris pump does not have the volume of a V8 engine oil pump and there is a remote possibility that air could cause the pump to lose it's prime, therefore Polaris recommends that the vent line be pinched off utilizing crankcase pressure that is normally vented to the air box to pressurize the oil tank.