Unscrew those grease nipples……put the nipple in your gun and see if grease goes through it….If not…..replace with new ones…If it does go through…you will need to pull out the shaft from the skid and take a small drill bit and drill out the tube because someone did not…I just put an M-10 in mine 2 days ago and found the same problem with my upper rear shaft (with the two tip wheels)…..
After removing the nipple use a small center punch to mark the hole…Carefully with about a 3/16 bit, drill it out…make sure to clean out the cuttings and you may need to use a round file to remove any burs on the inside…Its an easy fix……I have had the same problem on a couple Polaris sleds…..Check once to make sure the shaft goes in….pull it and grease it up with a wad of grease on a rag…..reinstall…give it a few pumps with the gun and you should be good to go…..Bye the way I did let FAST know about mine……It’s a great skid you will love it….JD