Ok guys I have a 2010 klx 250fs modded air box full fmf exhaust one down sprocket stage 2 dyno jet carb it tops out 82-84 I want to go faster more power I’m 220 lbs bike won’t clutch up in 2nd will a 351 kit solve my problem or should I go lower just want a little more power and on YouTube the 351 kits I watched topped out around 90 how can 100ccs only give u 8 more mph advice please and no I don’t want a bigger bike I like the light 250

 

You can only go as fast as the rpm lets you. Big bores don't jump the rpm up, so speed isn't added, except that the power allows it to push a bit harder at the top. Thing it will allow is to gear up a bit taller to gain a bit of speed.