missing at cruising speed

my '78 kz 650 just recently started sputtering and missing at cruising speed (about 3 or 4 grand) and i am not sure what could have suddenly happened i bought new spark plugs and readjusted the timing and it still does it but i had it running great before and i haven't done anything different to it so any ideas or suggestions would be helpful. thanks

3 or 4 grand is where the advancer starts to move the timing forward. Check that, they get sticky, rusty. It should be lubed once in a while.

double post

Post edited by: OKC_Kent, at: 2007/10/15 11:58

If you have a fuel filter on the bike, remove it and install a new one. Check the screen inside your gas tank on the petcock. Make sure that a vacuum isn't setting up in the tank by having clogged gas cap venting. Next time you get the miss, open the gas cap and see if the problem goes away as a result. You might also check your coil voltages... see our tech tip called "Coil Repowering" under wg's Tech Stuff Index on our website.