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Discussion Starter · #1 ·
Let me start by saying I'm an old guy that loves working on anything with a motor to keep himself busy. I recently received 2 Polaris Xplorer 300's with low compression issues. One is a 98 the other a 96. I rebuilt the 98 and bench tested the oil pump. It pumped fine. I put 2 gallons of premix in, and it started and ran fine. After a few runs I disconnected the oil line to the carb and noticed the oil pump was not functioning. Decided it would probably be a premix only machine. I did everything the same on the 96 except this time I noticed the drive shaft on the oil pump (worm gear shaft) was allowed to move in and out close to 3/16 of an inch. When I bench tested the oil pumps the shaft was not allowed to move because of my drive fixture. I took the cover off and the pin that holds the gear from moving in and out was missing. Problem solved. Being old with little to do, I removed the engine on the 98 and the oil pump had the identical issue. I don't have any history on these machines, other than I know they were rebuilt before because of the .020 over piston in each. Can anyone shed any light on how these machines could be 25 years old with that pin missing?
 

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Discussion Starter · #3 ·
I'm a retired machinist, and I agree with what you said. I did the measurements for the free play with the worm gear and the end of the drive, and it should stay engaged. Although it would be close. It seemed unlikely that the worm would fluctuate back and forth instead of turning the pump gear. But they now both work with the pin in place. I ran at least 2 gallons of gas through the 1998 before I pulled the oil line off the carb. And it worked almost immediately after the pin was installed. I hesitate to ask, but I have another question on the oil pump. I was unable to remove the pump sleeve in the motor. The sleeve with the o-ring on the outside diameter. Since the distance between the sleeve and the pump were in spec, I didn't try too hard to get it out. Could this cause a problem with pump function?
 

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I'm not familiar with that particular design of pump but I'd doubt it from looking at the parts diagram.. or from my knowledge of the old jap oil pumps... but.. I did see they have shims for in there by that tube/sleeve. I'm not sure why that would be so critical since it's just the worm gear that has to engage, and you would think that would have plenty of lee-way.
If it's going now though.. Happy days.
 
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