I have a 1985 Honda 250 SX, with about 20 total hours on it (I haven't gotten out much with it). After not riding it for several years, I tried riding it today. It starts & runs okay, but starts to sputter at higher RPM's. Almost acts as if it's running out of fuel (kind of like vapor lock on a car). The fuel filter screen (in the shutoff valve) is clean. The spark plug is clean & appears to be gapped appropriately. I'm not sure if this tells anything, but I tried hooking up an automotive timing light (to see if it was the ignition system faltering), and it seems to quit at higher RPM's; however, after it quits flashing, it won't flash even at lower RPM's until I bring it back down to idle (even though the engine seems to be running fine at mid-RPM's). This makes me suspect that the timing light can't keep up with the flash rate of a 1-cylinder engine at high RPM's.
Does anyone have any suggestions on what to try?
Thanks and regards,