My KZ900 has had a rough idle for a long time. That and a lack of oomph were the reasons I "found" time to install another set of cylinders bored out to 1015cc. I wasn't sure what the problem was, the intake manifolds are a few years old, dyna ignition timed with a light, carbs cleaned many times.
The carbs I had been running were VM26's from Sudco. I changed out to a set of VM29's that I had sitting around. I cleaned the 29's before installing. Still the same problem with idling. When cold, it didn't want to idle, Adjust the idle speed upwards, then when the motor was warm it would idle too high and still be unsteady. I sprayed WD40 on the carb boots and didn't think there was a problem.
I noticed the #1 carb seemed to cough more than the others and figured I'd change the intake manifold even if it doesn't seem to need it. Pulled the carbs off, started unscrewing the bolt and.... it wasn't tight! Both bolts were a bit loose. Next I removed the manifold, cleaned it along with the head with brake cleaner, dabbed some permatex ultra black then reinstalled the manifold. Next day, started it up and the bike now idles better than it ever has since I bought it!
Lesson: check everything. I was looking for cracks in the intake manifolds, dirty pilot circuits and the problem was two intake manifold bolts that had worked loose or I forgot to tighten them.
1978 KZ1000, 1976 KZ900, 1975 H2, 1973 H1, 1973 H2, 1978 RD400, 1977 RD400, 1974 RD350
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