I`m looking for jet sizes for a 98 MXZ 670 all stock @ 2000ft.
altitude.

start with 300 on the pto side and 290 on the mag side. this should be a good place to start.

Stock jetting on the 98 mxz 670 is 310pto/290mag for 0'-3000'.

MAINS 310 PTO 290 MAG--- NEEDLE JET 224 AA3--- PILOT JET 60---7EDY1 NEEDLE 3RD FROM TOP POSITION---AIR SCREW 2-1/4 TURNS OUT--- 2.5 SLIDE CUT-AWAY

Awesome info guys. I`ve got those spark plugs looking like a perfectly done marshmallow.

What did you end up running? Mine was 2 sizes fat from the factory. I ended up with 290 - 280.