boring a cylender

[kickstartkx]

i have a 2004 kx 125 that im going to bore the cylender to a 56 mm bore making it a 134.2CC i know the extra cc will help performance but will it make a big diffrence because the porting was not designed for the biggger engine
it is about a 8% diffrence in size from stock
should i expect to feel 8% more power or not because of the porting being designed for a 134CC motor
i did a little bit of porting my self to aid in more flow witch i think would help because a bigger engine needs more gas and air
would i expect to lean , richen or keeps the same on my jetting
it runs on the rich side now
By the way it has a castiron sleave in the cylender.

 

[viking20]

If you have a cast iron sleeve , the bike probably ruined the cylinder at some point. If you just bore the cylinder bigger , the ports will need adjusting , or timing of these will be wrong for most people.
When a cylinder is fitted with a steel bore , the piston will have to use a different clearance than with a plated bore , you might not be able to get a 56 mm piston designed to run with a steel sleeve.
Be carefull when you try to port it yourself , its best left to someone more experienced...
I would try giving Eric Gorr a call , if I were you ,he often has cylinders already done for sale.
You can get the porting done as you would like it , and you will have a fresh , plated bore....
The prices are extremely good...