General Jetting for Aftermarket pipes ?

H

Hilltop Cycle/ATV

Member

Apr 11, 2004

23

0

• Jul 19, 2009

• #1

What would be a good starting point on a 01' YZ80 with a pro circuit plat. pipe and a FMF powercore II silencer ? The jets are standard sizes from the factory . Just wondering if generally you go up on the pilot jet and main jet when you go to an aftermarket pipe or do you go down on jet sizes ? How much bigger generally , one ,two ,three sizes ?
Thanks,

 

H

helio lucas

~SPONSOR~

Jun 20, 2007

1,020

0

• Jul 20, 2009

• #2

http://www.procircuit.com/jettingspecs.htm
http://www.boyesen.com/cwo.php?id=14&id2=20&id3=&page_id=58
those give you a good starting point. normaly you have to jet leaner one or two steps on the main.

 

H

Hilltop Cycle/ATV

Member

Apr 11, 2004

23

0

• Jul 20, 2009

• Thread starter
• #3

what series of jets do i need to order ? there are so many ot is confusing and I have to mailorder and don't want to send them back and forth to get the right ones. There are like VM,TM,BS30/96,VM22/210, for the pilot jets and aren't there two different sized hex main jets ?
Thanks,

BTW: All i know for sure is that it is a 26mm mikuni ,has a hex main, and I need to tune it.

 

Patman

Pantless Wonder

LIFETIME SPONSOR

Dec 26, 1999

19,774

0

• Jul 20, 2009

• #4

Talk to local shops and better yet people you run in to at the races / practice with similar bikes. Jetting is part black magic and part science which changes with the weather.