4 Stroke Spark Plug Question

A lean condition sounds right. For two strokes, you would increase the size of the main jet, to get rid of lean bog at 3/4 or open throttle. I'm not sure if four strokes have the same jets and everything. I would assume that they do so try opening up the carb and looking at what size the main jet is, then get some larger ones to replace it with.

Things to check before going any further:
1. Is your air filter dirty?
2. is your needle still seated in the carb with the clip? (this same thing happened to me).
3. What is the color of the plug at 3a. the bottom ring, 3b. the farthest up the insulator that you can see (hopefully it's not white).

if 1 and 2 are ok, then you need to make some changes:

A. You are too lean on the pilot jet. Make adjustments (out) in 1/4 turn increments to the fuel screw (small screw on bottom/front of the carb). the bottom of the plug should not be bone dry.

b. Xr's typically do 2 things when they aren't jetted right. If it revs but doesn't make power, then it's lean. If it sputters it's rich.

What is your main jet size, what pipe are you using, what spark plug?