quick question - I just got my je piston today, I wanted to be sure about mounting the piston. The arrow should point toward intake, correct? I can see on the top of the piston the size difference between the intake and exhaust valve clearances. I just wanted to double check.

Thanks, ogre

 

I'm not sure of the direction the arrow is suppost to go, but make sure you check valve clearance because I just got a TC cam and 87mm JE piston for my 400ex and the valve reliefs in the piston were cut wrong from the factory so I had to have the piston sent back.

 

You need to know which way the arrow should point because the valve relief on the intake side of the piston is smaller (diameter); obviously, because the diameter of the intake valves are smaller.

This brings up a quick question; I will be reassembling my 400 soon, how can I be sure that my valves will clear my piston? Manually turn over the motor and listen? I'm sure they will, I have an 87 mm 10.5:1 je piston w/o a cam upgrade, but I've never upgraded a 4 stroke with an aftermarket piston.

Thanks, ogre