Took head off to see what size piston. It was stamped 38B on top of piston, can’t find anything online about it except standard bore is 83.00mm and that should be stamped 38A. Anyone have an idea of what 38B bore is?

 

Sounds like the engine may have been re-bored to a larger piston size in the past. Some companies identify oversize pistons by a letter. "A" is normal, "B" is maybe a few thousands oversize, then "C". a few thousandths larger and then "D", usually the largest oversize. I never saw an "F".

However, due to problems in the castings, or machining issues, sometimes the factory bores out the cylinder to an oversize piston in a new engine and you find it in your brand new ATV, Motorcycle, truck, car or boat. I rebuilt a Ford 302 back in the 80's that had 3 oversize pistons and it was bought brand new by my mother 9 years before.

 

It seems that Polaris has three piston sizes for that engine and year. Standard, .25mm and .50mm oversize. Interestingly, it seems the oversize pistons are quite a bit cheaper. Naturally, they also sell oversize rings.

looking around the net, I see markings of 5W25 for .25mm oversize and 38B50 for .50mm oversize on the top of pistons. The standards just have a triangle and a 3 digit number.

 

Mine has a triangle then 38B opposite of triangle