i had piston problems on my 400ex and had to send it to the shop. I found out that i am going to need to bore it.

my question is: will this add power and speed? if so, how much faster will it make my fourwheeler go? and will it add a noticeable amount of power?

 

it depends on how big you get it bored.

 

A bigger bore will give it more power, however it not not make it faster (top end) unless you change the gearing and/or the cdi.
Your top speed is limited by the gearing and more importantly the cdi. The engine with still only turn the preset amount of rpms that the cdi allows.
A bigger bore can make your quad quicker (not faster) and will give it more torque.

 

You may get to your top speed quicker with the increase in power. But if you have the stock gearing even 1,000hp will still get you to the same top speed you had before. You'll need to drop a few teeth on the rear sprocket or add a tooth on the front to increase top speed. You will notice a difference with an over bore. Gain the most out of the new piston by going with 11:1 compression.

 

hey sprayedgt ...what you think bout the 12:5:1 piston..I got that in my quad and I wouldnt go to anything else!!