1981 KZ550C LTD running issues


New Member
Hey all,

Not sure if this is the correct spot for this.

I picked up a 1981 KZ550C off someone that couldn't get it running.
After a couple months of work I've managed to get the bike running, but I'm having some issues.
The initial start is very difficult. Have to crank it for several minutes, then manipulate the throttle slightly to get it to start.
After letting the bike warm up for about half an hour, when I rev the throttle, the rpms bog and the bike dies. I've tried driving it down the alley in gear but it has no power and will bog down and die if I go past 1/4 open throttle.

The following is the work I've done to it.

-New spark plugs. I'm getting spark at all the plugs but it looks weak to me. I measured the resistance at the ignitor coils and I'm getting 2.0 ohms. The manual says I should be at 3.2 to 4.8 ohms
-Carbs disassembled, cleaned in a sonic cleaner, rebuilt with a brand new rebuild kit with stock needles and jets.
The carb has been set up according to the factory settings found in the maintenance manual.
-installed all 4 new choke flaps.
-installed a factory airbox(PO had pods)
-Removed the valve cover and counted the pins for the timing chain which are correct.
-Removed the timing advancer to make sure its not seized and moves freely. The advancer is set to the T mark when #1 and #4 cylinders are at TDC
-Brand new battery
-New fuel and inline filter
-I checked the valve clearance and they all seem to be within tolerance.

Two of the airbox boots seem to be a bit short but still partially cover the carb. while idling I sprayed carb cleaner around the boots before and after the carb and there was no change in RPM so I don't think there is an air leak there.
However I've got all 4 new air boots arriving early next week.

Like i said the coil resistance is 2.0 Ohms. I'm not sure if that would cause a loss of power.
I tried adjusting all 4 fuel/air mixture screws by about half a turn both rich and lean and didn't seem to resolve the issue.
The bike has a 4 into 1 exhaust from the previous owner, not sure if that with original jets would contribute to a loss of power?

I'm really running out of ideas here and don't really know what to try next. Any help would be greatly appreciated.



Been Around the Block
Sounds like the pilot circuits in the carbs are still clogged. When you cleaned the carbs last time did you spray carb cleaner through all of the passages to verify that they were open?


Over 10,000 Posts
Clean the carbs again, use compressed air and carb cleaner and blow through all the small passages

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