Polaris 800 Durability replacement Piston kit (CAST - or - FORGED)

** NOT FOR USE IN TURBOS **


THIS KIT INCLUDES (CAST - or - FORGED) MCB DUAL RING PISTONS! (choose from the drop down menu)
This is a Durability "replacement piston kit" for Polaris 800 monoblock Dragon / Switchback / RMK all monoblock CFI motors. This kit is designed for use in ORIGINAL MCB FULL DURABILITY KITS ONLY !!! If you have a different suppliers "durability kit" then this kit will not work !! This is just for replacement - Pistons/Rings/WPB - 2 New Base Gaskets 1 - Y-pipe Gasket. Again, these are to be used in MCB DESIGNED KITS ONLY !!!

MCB's durability kit was designed for improving the reliability / durability of this motors design. It used .240" taller pistons, with tighter tolerances and less skirt taper. This reduces the piston "rock" or "slap" improving the reliability of this motor. This kit includes taller pistons, dual rings, pins, clips, wrist pin bearings, complete top end gasket kit, (factory style coated metal gaskets), machined .240" shim and the extra base gasket for the other side of the shim, eight new .240" longer bolts (not shown), two .240" taller dowel pins, instructions for installation with torque values.

Polaris 800 CFI fix it explanation

The stock 800 CFI motor runs a piston that is a total height of 2.885". The stock piston to cylinder wall clearance on the CFI motor runs from .0070"-.0090", this is considerably larger than the typical piston to cylinder wall clearance of most other water cooled two cycle engines of .0045". The stock piston also has a considerably larger taper from bottom to top .0026". These three main factors (short piston, larger piston to cylinder wall tolerance, and larger taper top to bottom) allows the piston to rock or slap within the cylinder. This results in premature ring wear, loss of compression and eventually piston skirt failure or cylinder skirt failure. The MCB fix it kit uses a piston that sets the piston to cylinder wall clearance at .0055". It uses a piston that has significant less taper, and is .240" taller or 3.125" total height. These three factors eliminate the rock or slap described above, improving the reliability. Stock fuel mapping is as lean as it can be for emmissions. This causes "hot spots" in the fuel mapping and can cause the piston to swell, this is why we run the piston to cylinder wall clearance at .0055" instead of .0045". We MCB recommend a slight fuel map change and the use of Ice Scratchers to optimize the cooling of the motor and eliminate the "hot spots" that can cause cold seizure like failures, especially if ran at the tighter tolerances other than what we MCB recommend.



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