I've got a Honda 300 Big Red with a very strange fault. It is a bad starter but once running is OK except for a flat spot at just above tickover. Open the throttle too quickly and it stalls, but once above that it will rev fine, you can blip the throttle no problem as long as you don't let it drop back to a steady tickover. I changed the carburettor, coil and plug, re-set the valve clearances, with no difference. Checked compression, 150 psi. One other symptom, give it any choke and it won't offer to start, or give it choke when running and it stalls. Plug colour is spot on, brownish grey electrodes.

 

Solved it! As a firm believer that CDIs are either right or dead I was loath to get a new one but couldn't find anything else wrong so got one, put it on, and the bike starts like a 300 should and has no flat spot. Another odd thing with the old CDI was it "ran on" for a couple of seconds when you turned the ignition off. It doesn't do that now.