erratic engine performance

I recently acquired a 1976 KZ900 B LTD with 9000 original miles on it.  Since the bike was stored for many years, the bike was sent to a restorer in Ohio, and had typical work done to make it usable: fuel system cleaned, new intake manifolds, new plugs, valves adjusted, fluids changed, new fork seals and the master cyl rebuilt,  The restorer said a Dyna ignition was needed, and installed.  However, he only installed the Dyna plate, either failed to or set the ignition timing incorrectly, and did not change out the original ignition coils.  I needed to purchase the Dyna 3 ohm coils that are matched for this bike and ignition system.  I'm waiting on new K&L carb rebuild kits, as bike still does not run great.  I put a compression gauge on the motor and all cylinders were 99-105 lbs.  A 4 set of bike vacuum gauges was used and calibrated to each other.  The gauges all read about the same value, but all fluttered about 10 inches up and down 5-15 inches.  My question(s) low but even compression in all cylinders, similar low and erratic carburator vacuum values.  The engine header pipes are discolored a brownish tint.   I What could be  contributing to these conditions?  Possible incorrect valve adjustment/shims?   Possible frozen piston rings?  Burned valves?  Bike takes a long time to warm up.  Once the bike is warmed up it runs and rides well,  What could be causing these unsettling readings? Any advise is welcome!  Thanks. 

How far have you ridden  it ?  The rings might  release and start to seal better .. Have you rechecked compression and what method did you use  ???
Tune it up completely  and let us know what happens
Pictures will  always help hold our attention 
Dave

The Dyna S points replacement kit is designed to work with stock 5 ohm coils.  Dyna 3 ohm coils are okay, but on the low end of the resitance range for the kit.  Point being, the rebuilder didn't do you wrong there.

As Street Fighter mentioned, you need some miles on the bike before a proper compression test can be performed.  The 'ol Italian Tune Up is called for when bringing an old bike out of long term storage.  And when doing a compression check it's important for the engine to be hot and the throttle held wide open.  

Carb kits, particularly K&L, are suspect. If the carbs are still dirty they need to be fully taken apart and the carb bodies soaked in carb dip to clean the internal passages.  Slamming in some aftermarket parts is NOT a carb rebuild.  Short cuts are long cuts.

 

Your carb problem could be caused by a couple of things.  You can check one easily.  With the bike idling in neutral spray a little carb cleaner on each carb boot on the intake manifold.  If the rpms rise then you have leakage.  Tighten the clamp.   

Second, your choke plungers are probably leaking a bit.  Maybe one or maybe all of them.  There is a seal on the bottom of the plunger that wears in over time, allowing fuel to leak by.  They should be replaced.  Zed1015 on this site can fix you up.

Based on the fact you say it runs good after it’s warmed, I’d wait this out till you have more miles on it. These bikes are typically cold blooded. They are not start and go like fuel injection. Did you adjust the dampers correctly while setting up the vacuum sync gauges. If not that is the problem with the fluctuation on the vacuum. I would suggest you get a factory service manual and do all of the periodic maintenance adjustments described in the manual. Check the battery and charging systems also.