Need help with jetting

[hardkoratvmxr]

My motor is getting a .060 over 11.1 compression piston and new intake valves ( stock size ). I also have a K&N closed air box and an HMF slip on with stock header. Before getting the piston and valves i had a 128 main, sotck pilot, needle moved down one notch and it ran fine. i just want to get a good idea on how many main jet sizes i should go up. o yea the plug i pulled out was a golden brown so i had it spot on before.

[reconmaster]

it shouldn't change anythign just wait till you break it in then check your jetting

[hardkoratvmxr]

yea it should because i have a bigger piston

[Sjorge450R]

Originally posted by hardkoratvmxr
yea it should because i have a bigger piston

acually, its going to be real close. Just put like a 135 and see if it boggs down and go from there.

[bwamos]

I would agree. It will change some, but not a whole lot. Simply, because you're running with the airbox lid on and unpunched. You're airflow restriction before the overbore is the intake.. that restriction remains the same after the overbore.

You could try the 135 keihin.. but I'd be willing to bet that that would be too rich with the airbox lid on. 130 keihin would probably be more accurate. Swap the lid with a Prefilter lid, and you'd be around a 140 keihin.