KZ 750 4 stumble

Old age has caused me to downsize. Picked up a 1982 KZ-750 4 cyl last fall- Love the bike with exception of the following
From a standing start the motor seems to be leaning out- poor power until 3000 Rpms- Bike is strong runner above that rpm. This is also a problem when riding at speed and rounding turns and accelerating out of turns unless Rpms are kept above 3500 or so.
Any ideas would be appreciated?
P S The carb intake boots seem to be in good condition

Couple of possibilities come to mind.
Imperfect pilot circuit (needs cleaning);
Too tight valve clearance.



Symptoms of marginally too tight valve clearance are usually worse at lower rpms.

Good Fortune!

Just to add to Pattons post
When I bought my 1980 750/4 several years ago I had a persistant stumble at about 2500 - 3000rpm. To make a long story short it turned out to be dirt at the pilot bypass. See #3 in the attached schematic. If you think this might be your problem then look for 3 tiny holes at the indicated location just behind the throttle butterlfy and poke them out with a fine needle or bent @ 90 degree guitar string and do the spray procedure which Patton describes above.
Wear eye protection

Good luck