76 KZ 750 B Twin issues

I have been working on this bike for a while now.  Got it as a rolling frame and a box of parts. 
I have it running,  Kind of....
I can not get it to go above 3k rpm or it starts choking, sputtering and backfiring.
I have cleaned all carbs (have not gotten a rebuild kit yet, but everything seems clean)
Fuel mix screws have been re-seated, and backed out 1 and 1/2 turns, (adjusting the mix screws seems to make little to no difference in the idle, unless completely seated, then engine dies)
timing light flashed properly at the F mark. 
I am lost. This is my first bike, and first time working on a bike. Any ideas / help?
Or even better, if anyone in Ohio is willing to come take a look at it? 

What state is your ignition in? 3k is about full advance. if the advancer springs are worn out or the advancer is stuck you bike will run poorly at high RPM.

I know very little about the advance.  I know there are 3 screws to adjust on the plate behind the points.  I fear I know little more than that...
is there a rebuild kit for the advance?

Use your timing light. As rpm raises the F mark will move away from the index line on the case. If the F doesn’t move the advancer is stuck.

Thank you.  I shall be attempting tonight.

ok.  so after getting timing light (borrowed the last one) it appears to be firing before the F | mark.
when I dial up to 30 on the light,  It is right on the mark.  
I will try to include video of timing, and of light dial mark
Initial timing, light set at 0
art-innovate.com/bike/video-1.mp4
Timing light adjusted to 30
art-innovate.com/bike/video-2.mp4
Timing light adjustment
art-innovate.com/bike/dial.jpg
As always I am most grateful for any assistance.

In your original post you mentioned with a timing light it was on the F mark. I mentioned to use the timing light and watch the F mark as you increase rpm. The F mark should move away from the timing pointer cast into the case, if the advancer is working. So, you have proved is the bike is not timed correctly. That will most definitely cause it to run poorly. 

1. Did you check that the advancer is working?
2. Did you reset timing as described in the manual DoctoRot posted?

The advance dial on the timing light does not correlate directly to degrees on Kz.  The light's advance knob is usually calibrated for a car using a mechanical distributor.  This means the light is expecting to see one fire every 720 degrees of crank rotation, but on the Kz it sees one fire every 360 degrees of rotation.  As such, the timing knob is off by a factor of two.

If the knob reads 30 degrees, you are seeing the strobe flash at about 15 degrees of Kz crank rotation after the actual fire happens. 

So ideally on the Kz, when the knob is set to zero, the strobe should flash when the F mark is lined up (at idle).  When the knob is set to double the Kz's timing spec., the flash should happen when the T (TDC) mark lines up. 

The Kz timing marks are very convenient in that it gives us an F mark, so we don't really need a light with an advance knob.  I just leave it at zero.  I actually put a piece of tape to hold it at zero because if you unknowingly bump the knob and set the timing, it will throw off your timing.

At higher RPMs, there may be a further set of timing marks to indicate the timing at full advance.  Sometimes it will be two marks and the timing needs to be anywhere in between those marks.

It's hard to see where the flash is happening on the video due to the nature of how digital video scans the image over time.  That's why you get that moving flash appearance. If you have a slow-motion capture ability, that will probably give a better result.  I'll try to look again at the videos.

From what I can tell, I agree, the timing looks a bit to far advanced.

thank you,  Yes,  I did use the timing light, when I throttle to higher RPM,  the timing marks do advance (and move back when I release throttle)
I set the static timing by aligning the F | mark on the on the compression stroke and setting the points to a gap of 0.330 (using gap gauge)
sorry I did not mention in last post

wrote:

The advance dial on the timing light does not correlate directly to degrees on Kz.  The light's advance knob is usually calibrated for a car using a mechanical distributor.  This means the light is expecting to see one fire every 720 degrees of crank rotation, but on the Kz it sees one fire every 360 degrees of rotation.  As such, the timing knob is off by a factor of two.

If the knob reads 30 degrees, you are seeing the strobe flash at about 15 degrees of Kz crank rotation after the actual fire happens. 

So ideally on the Kz, when the knob is set to zero, the strobe should flash when the F mark is lined up (at idle).  When the knob is set to double the Kz's timing spec., the flash should happen when the T (TDC) mark lines up. 

The Kz timing marks are very convenient in that it gives us an F mark, so we don't really need a light with an advance knob.  I just leave it at zero.  I actually put a piece of tape to hold it at zero because if you unknowingly bump the knob and set the timing, it will throw off your timing.

At higher RPMs, there may be a further set of timing marks to indicate the timing at full advance.  Sometimes it will be two marks and the timing needs to be anywhere in between those marks.

It's hard to see where the flash is happening on the video due to the nature of how digital video scans the image over time.  That's why you get that moving flash appearance. If you have a slow-motion capture ability, that will probably give a better result.  I'll try to look again at the videos.

From what I can tell, I agree, the timing looks a bit to far advanced.

so... if I am reading this right, I would adjust the plate 15 degrees counter-closckwise?

What condition is the battery. It must be good and able to take and maintain a charge. At rest voltage should be 12.6 volts. A backyard mechanic test is to keep your multimeter on the battery. Turn the run/stop/run switch to stop. Turn on ignition and headlight if it does not come on with ignition. Watch meter till battery drops to 12.0 volts. Turn everything off, remove meter, let the battery rest for about 15-20 minutes. Use meter to check voltage, it must return to 12.6 on its own. If not the battery is suspect. You can pull it and take it to a auto parts or a battery shop to diagnose further.