0.028
The most common reason for a Honda 400EX not to fire is the need for a new spark plug. Try replacing the spark plug to see if that fixes the problem.
You need an 18 mm spark plug socket.
The gap for this car is 0.024" to 0.028."
The stock spark plug is the NGK DPR8Z gapped at 24 to 28.
According to the spark plug manufacturer NGK, the recommended gap for a 2001 Honda XR100 is .028"
Get a spark plug socket and unscrew the spark plug and replace with a new one.
.044
if you buy a new spark plug for your 2001 xr80r and it has a gap setting, set the setting all the way to the top of the plug as far as you can get it.
It is very simple in between your engine head uner your headlights you should see you canble running to it
18mm. But it has to be a thin wall socket. The stock tool that came with it is best if you can find one.
.020" to .025"
you need a special 18mm socket wth very thin walls. i got mine from pitposse.com, it cost $20.