Hi all, just an old guy here that likes to work on anything with an engine. I tried to post this question once before, but I can't seem to locate it anywhere so I will try again. I recently received 2 Polaris Xplorer 300's with very low compression. One a 96 the other a 98. I tore the 98 apart and replaced the crank seals and did a top end. I also bench tested the oil pump and it worked fine. After reassembly I filled it with premix and it started and ran fine. After several runs I removed the oil line from the carb and noticed the oil pump wasn't working. Decided it would be premix only. I did the same procedure on the 96 but noticed the drive gear (worm gear) on the oil pump had close to 3/16 in and out play. I took the cover off and the pin that prevents the shaft from moving in and out was missing. Problem solved. Being old with little to do I pulled the motor back out of the 98. The pin was also missing on that pump. The drive I used on bench testing didn't allow the shaft to move, so I didn't see the problem then. Now both pumps work fine. I have no history with either machine other than they both had .02 over pistons in them when I tore them down. Can anyone explain how these pumps could have functioned as long as they did without the pin.
Many novice mechanics took the cover off the pumps just to see what was in there and probably more than half that did, turned the pump over and never saw the pin fall out. In some cases the pump was replaced with a new one - in other cases the pump was reinstalled and never used enough to be a problem - the pump is not positive and oil can flow through the pump when it the engine is not being run - it's one of the reasons the motor smokes heavily upon startup and has to run about an hour to more or less quit smoking. Also while running a low speed oil will be drawn from the pump by vacuum. Anyway - congratulstions on being observant enough to find the problem and fix it.
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