Check firing boxes should be under seat one on each side.
SOURCE: honda 1986 vf400f nc13 engine front two cylingers not firing help
If the spark appears to be weak only for the two front cylinders, then I would suggest checking the electrical connections for the ignition coils.
If the spark for the other two cylinders looks the same (yellow), then I'd suggest checking the compression on the non-functioning cylinders. A compression reading of 140~160PSI is what you're looking for. Low compression indicates internal engine damage - or could be from something relatively simple - like insufficient valve tappet clearance.
If the bike has been sitting for a long period of time, it could be that the carburetors are plugged up with fuel varnish. This can cause some cylinders to not run. A complete carb disassembly and clean-out will be needed.
Testimonial: "thanks for that feed back . there is plenty of fuel and compression is non existant on front left and 80 psi on front right,I suspect cam wear????"
SOURCE: 1985 honda VT 500c shadow one cylinder when engine hot
how do i check the cooling fan to see if it is any good
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