Guide me step a to z for jetting the carb on an 08 yfz 450, i have an hmf and needs to jet it, but it is ported, what does ported mean, and wtf is a spark arrestor

 

A spark arrestor keeps hot stuff like sparks from coming out of your tail pipe. You need to have one to ride national forests trails and some state forest trails. I can't help you on the rest. I know what porting is on a 2 stroke but not a 4 stroke. I guess we'll both find out.

 

Yes, the spark arrester for performance exhausts is generally a screen placed at the end of the can to stop sparks from exiting and starting fires. HMF uses a small, dome shaped screen usually.

Porting is the same general thing 2 or 4 stroke in the sense that the areas fuel enters/exits the cylinder are getting smoothed, polished, enlarged. The difference is on a 4 stroke you get the valve area cleaned up in the head, and a 2 stroke the transfer ports on the cylinder walls are what is altered.

The good news is HMF has a great website that gives jetting specs that should be pretty close in your case. Be sure to hop on over to the forum for further info or if you need more help. A lot of great jetting advice over there.