Was running good but left cylinder stopped running

[Joeschwab]

Rebuilt motor completely it is bored .2 over it has decent sized porting running 300 main and not sure polite size 16cc cool head dome vforce reeds. Was riding at the track Sunday and all of a sudden left cylinder stopped rinning so when I got home I check compression I got 150 psi and I'm in colorado so that's about right cleaned carbs and it Semmes to be running again then I took it out it ran good for a couple pulls and now again same issue not sure what the problem is

[thomas h.]

Eletrical issue I bet. Check harness

[Larry's Shee]

Check that the filter on petcock is good. Might not hurt to clean inside of tank. Also check fuel cap vent.

[Seanzaay]

Check your plugs I remember I didnt tighten my plug all the way once and the left cylinder stopped firing.

[trickedcarbine]

Those dumb ass twist on tops for NGK plugs...