How much do i mill the head on my 2008 honda trx 450er?

Question

want to raise the compression but dont need a piston yet.

the bikes new and im putting an hrc cam in it.

Answer 1

As a rule of thumb..You dont want to go over 20 thousands..

to be safe.....If you want to go any more then that you have to take the motor to the shop and they will putty up the head to see how much room you have....

We use to go 20 on my sons bikes and it made a huge diff....

Answer 2

Buy a crf head gasket. it will raise compression some, but not a whloe lot. Make sure uit is jetted right, and you may have to run race fuel.