AkRacing Garage                            Polaris 440 PreMix Mod                                                 AkRacing

Here I will describe one way to prolong your Polaris motors that do not have oil injection.  If you have any '04 or newer 440 or 600 that is not oil injected you should consider performing this mod.  This mod allows extra PreMix fluids to reach the center bearing and water pump shaft.  It is recommended that you split the case to perform this modification but if you take the proper precautions you can perform the mod without splitting the case.  If your sled has been races extensively or had more than 500 trail miles it would be best to split the case so you can add another helping of IsoFlex grease to the Crank Bearings.  Splitting the case would ensure several thousand trouble free miles.

This procedure will describe the steps to perform this modification without tearing the motor down completely.

1.  Pull PTO Cylinder and clean all gasket material from the upper case and Cylinder.  Do not allow any debris to fall into the case.  As you remove the gasket material wipe away the gasket shavings often to minimize any debris from getting where it's not supposed to be.  Pay special attention to the Water Pump cavity toward the front of the motor.  If any pieces of gasket fall under the crank or in the water pump cavity, immediately take the time to get them out with a long sharp pointed poke.  A poke with a 90* tip is also useful.  Here are some pics of the cleaned Case before the Mod.  The case should clean and ready for reassembly before going to the next step.

2.  Next build a dam out of a blue paper shop towel to prevent and drill shavings from getting into the crank case.    Wet the towel with WD-40 or similar oily lube so it sticks to the case and tucks into the corners of the of the case.  Use your poke to tuck the towel into all the nooks and crannies of the case and counterweight. 

3.  Devise an adaptor to neck down your shop vac so you can vacuum the shavings as you drill them.  I used a fuel jug spout and wrapped a small hand towel around the spout and stuffed it into the shop vac hose.  Make sure you can pinpoint your sucking while you are drilling your hole.  Mark your hole with a Snap Punch, if you don't have a snap punch just use any punch to mark your hole.  The hole is put in at a 45* angle toward the water pump shaft at the front of the case recess in the case this would be toward the exhaust of the motor.  Make a 45* template out of shoe box card board and tape it to the Head Stud to use as a guide for drilling your hole.

4.  The cast recess in the case is a place where oil accumulates as the motor is running.  Make sure you drill your hole so its in the bottom of the recess not into the side.  Any liquid that would accumulate in the recess should be able to drain right down the hole.   Use a tie wrap to tie back the piston so it doesn't move.  Use a Sharp New 3/16" drill bit to make the hole into the water pump cavity.  Use the angle template to line up your drill and begin drilling into the case.  Keep filings clear with the vacuum positioned right next to the case and drill bit.  Clear the drill bit of shavings often especially when you get close to penetrating through the case.  The case is just over 1/2" thick where you are drilling.  The cases are very soft so drill slowly with very little pressure.  Do not allow the vacuum to suck up the dam you made out of the paper towel. 

5.  Use the vacuum to suck out the hole after you have drilled it.  If you think shavings may have fallen to water pump cavity you can turn the motor up side down and suck on the hole.  It will pull air from the other hole under the Mag side Cylinder.  Remove any big shavings before removing the dam.  Use the pick to carefully remove the dam ensuring no shavings or debris fall into case.

6.  With the dam removed and all debris cleaned out of the case it's time to prep the motor for assembly.  Dribble about 1 to 2 ml of 2 stroke oil down the new hole you just drilled, also hit the big end of the rod and a little down each counter weight.  This extra oil will provide lubrication to the center bearing and gears and help ensure long bearing life if a few particles of aluminum fell into the cavity.  Reassemble motor with new gaskets.  Torque base nuts to 28ftlbs. Head nuts to 22ftlbs. Motor is ready for final assemble and installing into the chassis.

The above motor was a 440 from a '04 ProXr raced during the '03-'04 SnoX season then retired to the shelf till '06.  It raced about 8 races and lots of practice laps.   These pictures were taken of the motor after it sat on the shelf for about 2 1/2 years and then was disassembled to make this modification.  You can see the piston wash that was left by the race fuel when the motor was in the race chassis.  This depicts about .240" wash, just a tad under 1/4".  The motor was completely cleaned, Reeds, EV's, etc.  trail converted and reinstalled in the chassis after this mod.  As of 03/15/07 this motor has seen about 800 trail miles and is running very good.  You can see in the pictures the condition of the original pistons.  The pistons and cylinders mic'd out good and were in good but not near new condition prior to this modification.  I performed this modification to an '04 and an '05 440 in Nov. 2006 and I am calling this a success as both motors have performed very good.