Wondering if anyone has ever ran across this and wondered? I am building my 2010 rzr 4 engine and need a balance shaft. I realized the journal bearings are the same part number on all 800 rzr models but the balance shaft changes part numbers in 2011? I know the 11-up is sequential fire, and older ones like mine are batch fire but wouldn’t think that would make any difference. I’m sure the weights are different on the two different part numbers. The hot rods crank I’m putting in is a 4091 supposed to fit all years 800 rzr and sportsman. My question is this, if the crankshaft weighs the same for all years, and the pistons are the same, why 2 different part numbers on the balance shaft and which one is best? Did they change something later to make them run smoother? Any insite would be appreciated.

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