i have my engine and tranny apart to replace a spring on the shaft and now that everything is apart i can see that i need a new piston and valve seals also. the valve seals come with the gasket kit neway so im not worried about that but what kind of gains could i expect from a 10.1:1 piston and xr base and head gaskets. would it not even be worth the extra cash without a new cam to go with it. id like to get the cam also but i just dont have the cash. also what brand pistons are made for 400ex's with compression ratios in between 10.1 and 11.1 thanx in advance

 

Do the piston w/ high compression then when u get the money you just have to pull the valve cover and install the cam. Hott cams webb cams ... and a bunch more.

 

thats what i was thinking to but i dont know how long shes gonna be around after this. im trying to sell her so i can get a car by this summer

 

oops um wiseco je... and a bunch more i prefer wiseco.

 

Well if ur going to put a new pistion in it any way then do the higher compresson. I dont think there that much more. Im in the same place although i think im going to keep mine and work alot over the summer and have a car and a quad.

 

 

the bike won't run much different without changing the cam. the cam really opens the bike up. i prefer the je and ross pistons. the ross is the lightest. the wiseco just has incorrect compression ratios. the je and ross pistons aren't exact either, but are closer from what i read. anywhere around 1.6:1-11:1 shoudl be fine on premium fuel. make sure you jet it though. the hotcams are pretty cheap. i wouldn't even bother with the piston if you weren't going to change the cam. if you do both, expect a nice gain!!

 

ya thats what i was thinking, im going to put the piston in it now any way though becuase then if i dont sell it i can just put the cam in and not have to go into the top end. its only $20 more anyway...

 

My opinion is since the motor is apart, why not get a new cam, valves springs, and shortened valve guides, and install them at the same time you replace the piston?

But, if your thinking about selling it, then I can understand only wanting to spend some money for a piston - I guess every situation is different.

 

Yeah and every time you do it you have to buy gaskets... They add up quick!