kz550 carb issues

yes I read the dynojet manual thoroughly. The first day it ran nice and I never noticed anything odd. I pretty much drove it around town to test it out and then parked it and the next day my troubles began. I won't say that it was absolutely perfect but it was very drivable and would pull strong through most of the powerband without hesitation or bogging. The weather was not great here today so I could not test it further. Hopefully tomorrow I can drive it around and see what happens. If I have no luck I think I'll go back to the recommended 98 mains and dynojet needle at 3rd clip, resync the carbs and double check everything. I just can't think what could have changed to cause these issues. Like you said it should be drivable with the dynojet settings so if I find it not to be I'll have to start troubleshooting elsewhere. hmmmm...

Just to add, when I say "drivable", that is, with the bike fully warmed up. If it's lean just off idle, you'll get some popping in the exhaust when you close the throttle, when the bike is still cold.

I guess that is a problem.

jwe2 wrote:

I guess that is a problem.

1 and 4 look okay.

On 2 and 3 would:
a. assure correct ignition timing;
b. use new plug to check spark quality (want fat blue);
c. check for adequate compression;
d. assure correct valve clearances;
e. assure correct fuel level (use clear tube test method).

If sooty condition persists after above, would try leaning the carb pilot circuits.

Good Fortune!

For some reason I can't get a closeup on the photot, but it looks to me 1 and 4 are slightly rich, but 2 and 3 are really rich.

2 and 3 are fired from the same ignition circuit and coil. So maybe an issue there.

Best to rule out ignition first before going too far into carbs.

If the plug wires will reach, swap the plug wires at the plug ends... 1 with 2, and 3 with 4. Then swap the green coil wire and black coil wire. This effectively swaps the coils. (Whichever coil has the black wire fires 1 and 4, the one with green fires 2 and 3.)

If the plug wires won't reach, then try to swap the wires as necessary to get the correct lengths. I believe the plug wires will be removable on the 550 coils, but I'm not positive.

Then run it again and see if the plugs come out opposite of what they were like (come out 1,4 black, 2,3 lighter). Then you know it's ignition coil problem. If plugs stay the same, it can be igniter/pikups/wiring, or still the carbs.

But since all four are not the same, we know it's a condition/maintenance issue and not strictly a jetting/needle issue.

1 and 4 are light tan/brown, 2 and 3 are black. i was checking the wiring and noticed the green wire going to the coil for 2 and 3 was connected to the positive side. I can't remember which wire goes where, but i have a feeling the yellow/red wire goes to the positive side of the coil. I switched the wires and the bike immediately drove better. i'll have to wait until tomorrow to drive it more and check the plugs again. ill probably have to go back to the dynojet needles now.

if the coil was indeed connected wrong, how would i get those sudden bursts of power during the surging? wouldn't the coil just not work at all?

Coils can be intermittent.

The + and - shouldn't matter theoretically, but they must have been marked for some reason... maybe just uniformity in wiring. In either case, yes, yellow/red would go to the positive terminal.

Surging could also be an intermittent pickup coil. That is the pickup with the yellow and red wires. It could also be an intermittent igniter. And there's always the possibility that it is just some loose wiring somewhere or a bad connection.

If you have a timing light, you may be able to tell when the 2-3 is misfiring (if the problem is really electrical). Then you can use the light to determine if the misfire moves to different cylinders when you swap coils or pickups.

First is to swap the coils as I described. Then you can rule them out. However, if they are original coils, then you may want to get new ones anyway, if you are going to keep the bike. The ones to get are the gray Dyna coils. They are the 2.2 ohm ones. Z1enterprises should have them.

Ditch the inline fuel filter and see if that doesn't solve your problems

Is that fuel filter for a gravity feed system?

vacuum petcock

don't mean to interrupt... but, great info in this thread.

jwe2 wrote:

vacuum petcock

With a correctly functioning vacuum petcock:
Vacuum to petcock allows gravity feed fuel flow from petcock in ON and RES positions;
Vacuum isn't needed to allow gravity feed fuel flow from petcock in PRI position.

With a correctly functioning manual (non-vacuum) petcock:
ON allows gravity feed fuel flow from petcock;
RES allows gravity feed fuel flow from petcock;
OFF disallows fuel flow from petcock.

Good Fortune!