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gotta 78kz650b2....dyna ignition, wires, coil mod....started missing and popping the other night and the next day it progressively got worse....at 3/4 to WOT pulled and ran great....just cruising or at idle it popped, backfired, spit, sputtered.....I adjusted the cam chain, changed plugs, but still does it...I don't think it is a fuel issue, if so, it wouldn't run at WOT...originally posted in the engine section and tried some suggestions and came up with this....
checked the battery at idle....11.5 volts......at 4000rpm.....12.5 volts.......switched batteries with my other kz650 that had 12.5 at idle and 14.5 at 4000.....same thing...........charging issues.......what's next??????...I hate lectrisical stuff.............

I dunno sounds alot like the problem I had with my 650 before I got new jets... backfire popping at low rpms but at WOT ran and pulled great.. got my new jets in and no more missing and such runs great all the time.. sounds like you might have a couple of clogged jets but if you think its electrical you might try testing your coils and checking for good spark that would be where I would start.. if you've already done that check your timing

what rpm is does it idle at? And how smooth is the idle? Wanna know if u have a plugged pilot jet or jets? put your finger over the holes inside the carb mouths (one by one) If the motor idle does not change with each block, you have a plugged jet on the one that does not change the idle. Make sure that you don't have a sneaky intake leak or any spark jumping around the coil or wires. Loosen kill switch and make sure the little screw inside is still tight. Make certain there is no rust in the tank or youll be stumped forever. Screen filters do nothing for rust. Don't forger to examine the intakes closely. AS long as there are 11 volts directly to the coils there should be enough spark. Make sure the reley is not causing a voltage drop, as sometimes this can happen. plug boots should be ohm tested even if almost new. The resistance can change, if you test one that does not give a steady readin throw it away. Try fresh gas. Gas doesnt want to burn unless the piston speed is up and the temp gets high enough, given certain conditions.

Post edited by: nads.com, at: 2007/10/19 01:33

take a look at the plug wires and ends to make sure nothing has gone bad,
It sounds more like you might have a vacum leak around the carbs and it is getting lean in that range,
in addition to the jet question, do you have a inline fuel filter just wondering of you may have some trash in the carbs

will try everything this weekend......knowing my luck it ain't something simpl though.........