Jetting help

[t-balls400ex]

Recently bought a 1999 Honda 400ex has an E-series pipe and two 2 inch holes in airbox.The man I bought it from said his shop put a 170 main jet is this too big seems to run ok this is the only one I've rode.

[tj's400ex]

seems big, check the spark plug, what is it telling you? if the plug looks good I would check the jet to confirm the size.

that's what I would do. :)