how much does just boring a raptor out help like to a 686, how big can you go just boring? and who does it cheap?

 

1-4 hp depending on other modifications and compression ratio

102mm, or 686cc, or .080 over.

Just find a local machine/engine shop, its usually only about 40-75 bucks for a bore and hone depending on application.

 

if your looking for the 1-4hp gain from a 686. just have your head ported by a engine builder, and swap the cams and you'll gain over 4hp. it depends on what pipe your running also. you could pick up that much hp just by switching pipes.