Carb help!! pilot and main jet advice needed!!

Hey Guys I'm running a 76 kz900. I have a set of Mikuni 28's with a pump accelerater and a kerker pipe. when I start the bike I get a whole lot of back fires out the exhuast and some smoke out of the carbs!!! Ouch!! I'm thinking it's a gas issue any ideas or help would be great!! Also I'm pretty sure I have coil wires on the right spark plugs but am not 100% sure. I have a Dyna electronic ignition and dyna coils but the coils were not labled as far as firing pattern. I think I have it right but if I didn't would that also maybe be why the bike is running so ruff!! And last but not least what size pilot jet and main jet would be right for this set up?

Thanks in advance for all your help!!
JC

JC, You need to approach things a bit more methodically or you will go nuts. Leave the carbs alone for now. You can't tune them if your wires are not on right.

To check the wires, note your Dyna S has TWO pickup coils. The left is to fire the 1 and 4 plugs. The right is to fire the 2 and 3 plugs. Trace the wire coming off the LEFT pickup coil up to where you soldered or connected it to some other wire that connects to the coil. This will be a BLACK wire on many Kaw models but who knows what color wire you used? Anyway, this wire makes this coil the 1 and 4 coil. LOOK AT THE PLUG WIRES coming off this coil... they should go to the 1 and 4 spark plugs. If they don't remove the wires going to those plugs and connect the wires from 1/4 coil. Obviously, you should do the same with the right pickup coil which is the 2/3 pickup. The wire connected to the DYNA S wire that connects to the coil should be going to the LEFT coil and be green. Make sure the plug wires coming off the left coil (connected to the right pickup) go to the 2/3 plugs. OK, we have that taken care of...


OK the carbs. Your carbs are from a 79/80 KZ1000. First make sure the accelerator pump is working as it should... if you don't know how, this is kind of detailed and complicated. Suggest you consult a manual. You can CHECK them by taking them off the bike with gas in the bowl and pulling UP on the pump actuator lever to see if gas comes out each of the little spigots in the center of the carb throat venturi. If it doesn't, consult a manual or find pro help. Next, rejet... the 28s tend to be rich with a pump and bigger pilot jets. You can use the stock size #15s and while the bike will start and warm up a little cold blooded, will be crisper once it warms. You can also use the larger #17.5 pilots to get it started/warmed better but need to be very careful adjusting the accelerator pump so it doesn't get rich off idle (when throttle twisted)... again this is kind of a tricky adjustment. The main jets will be #102.5 stock and you can bump those to #115s with pods/pipes.