I have a banshee that needs to be honed before I put in new pistons. I am thinking oh just getting it bored though. I feel I will get more for my money since I have to do engine work anyway. What is an average price for a shop to bore a banshee? Also, what is the difference in .020 over, .040 and so on compared to like say a 370 or 420 kit (is .020 like a 370? does anyone know the calculation to figure this out?).
Thanks. Any responses will be greatly appreciated.

 

If there are no deep scars in the bore, I would go just to the next oversize. You don't gain much in displacement just with overbores. I prefer to not need a new sleeve by blowing away my overbores. I have even gotten extra bores due to Wiseco's crappy quality control. I am on the third '80mm' piston in my FL350R. The second was .002" larger than the first and the third is .006" larger than the second.

Here is the calculation for the displacement:

(bore / 2) x (bore / 2) x PI (3.14...) x stroke x # of cylinders

347.44cc for a stock Banshee
352.88cc for .5mm (.020&quot over
358.38cc for 1mm (.040&quot over

 

The Banshee engine kits you refer to are usually more than simple big bores. I believe the typical 370 kit uses a long rod which, among other benefits, often provide better torque (low end) than a standard Banshee engine. Other kits may stroke the motor, meaning that the rod is pivoted further outward on the crank lobes. There are numerous posibilities to engine kits and many are much more than simply boring the stock cylinder and slapping in a slightly larger piston.