I'm thinking about lining up some winter projects and I'm considering wiseco pistons in the TB's. How difficult is it to get in there and take the cylinder off? I'm thinking of going with the standard piston but I guess I really won't know what I need until I get them apart. What increments do the pistons come in? Should I have it ported while it's apart? Does the head need done if I do decide to port?

 

Wiseco offers pistons in STD, .020" to .080" oversized in increments of .010", other brands only go from STD to .060" in increments of .020". I've become pretty partial to the Namura Hi-performance pistons - they are moly coated and don't seem to be as "noisy" as the Wiseco's.

The cylinder is pretty much a piece of cake on the 250, unless someone has torqued the snot out of the 2 nuts on the clutch side, which will require removal of the clutch cover to access.

The 400 is a little more involved, but basically the same principle as the 250.

Any mods you are wanting to do (porting, head milling, etc) should be done while they are apart.

 

Since you already have other HPD gear....it's always a great idea to stick with the same company that made your pipe and clutch kits. The pistons and the porting will drastically wake up your machines. Also, your sig didn't mention any air filtration mods....that's also a great area to increase performance. Polaris offers complete ATV line-up service manuals. Not much has changed over the years, but since both of your's are 2003 one manual will cover both machines (you can also get model specific manuals for each of them). Make sure to retorque both machines cylinders after you get a good heat cylcle into the motor. Helps re-squish the base gaskets. [img]i/expressions/face-icon-small-happy.gif[/img]