Finally got a couple nice days so I took some time and wired her up, trying to get it to fire up before I tear it down to finish up the frame.
Not having any luck, good spark and compression, fuel down the cylinders it gives a bit of a backfire but no actual "run" just a backfire. I'm thinking the valves may be stuck?
Did you rejet & tune the carburetors for the individual pod filters?
If so, what main jets & pilot jets did you install and did you shim the jet needles to raise them?
Other stuff. service fuel level check to make sure the fuel level in each carburetor is correct.
Accelerator pump operating correctly >> fuel should squirt thru the carb bores without hitting the walls.
Mechanical synchronization >> throttle slides adjusted the same or about the same. the slides have a square opening or notch that probably should be completely above the bottom of the carb bore. I don't recall what the 81 manual says about the throttle slide gap, but the drawing doesn't show the notch. ....
I actually went back to the stock air box, decided I'd skip the hassle of fighting with jetting, may play with it after I have ridden it some, the carbs have been cleaned and gone through.
I'm thinking maybe there is an issue with the timing, I removed the cover that goes over the pickup coils, and it is fairly oxidized in there, I'm thinking there may be an issue with the timing advancer. Unfortunely someone has been in there prior to me and stripped the screw heads, was late so I just gave up for the night. I'm hoping to be able to remove the screws with some vice grips, or possibly slot them and try a straight slot screwdriver.
If the pulsing coil plate screws are damaged, use a dremel to cut slots in them so that a screwdriver can be used.
The KZ650-CSR came stock with electronic ignition, so there's nothing to set. What you should do, though, is clean, check & lubricate the timing advancer. check that the springs aren't stretched or damaged or anything. separate the rotor from the advancer body, clean everything, then lubricate the advancer & fill the groove with grease. lubricate the spring ends & pivot points. Reassemble & check that the advancer operates smoothly. hold the body, then turn & release the rotor >> it should snap back. Use a torque wrench to properly torque the advancer bolt. Install a new engine cover gasket.
Important note: Put a 17mm wrench on the big crankshaft nut to keep the crankshaft from turning, then use a 14mm wrench to remove the advancer bolt. You must use both wrenches. Do not turn the crankshaft using the 14mm advancer bolt >> timing advancer damage could occur. ...
Looks like it's been wet, maybe from sitting outside w a bad gasket. It should be clean in there with only minor oxidation.
I would use a penetrant on the screws. and vibration. heat from a heat gun might help as well.
Timing advancer lube. I use high temp brake & wheel bearing grease. dielectric grease & white lithium grease didn't work. doh.