Originally posted by 86atc250r@Jun 3 2004, 01:14 PM
Two things to remember when waiting for overbore "kits" with the 450R:
1.) The 450R cylinder is plated - so you can't just go out and have the cyl bored & slap in a new piston like a 400EX or 250R.
2.) With the 450R, any overbore what-so-ever will raise it above the limits for anything but the open classes in most forms of racing.
These two items will significantly reduce the options that become available for the 450R.
The last thing to think about is - how much power do you really expect to get from a simple overbore? Is it worth the costs of replating, possibly a new cylinder, a high priced custom piston kit, machine work, and thinning your cylinder walls which may adversely affect reliability (to get any significant cc gains, you will have to bore rather large)?
When changing the piston, the bulk of your power increase is going to come from changing the compression, not small increases in bore diameter. In my opinion - staying with the stock bore and increasing the compression a bit is going to be the best option for this engine.