TOPIC:

mizztheman   -  Noted the Glass-syringe.  The plastic syringes supplied with the Cleaning Tool can and usually will become "sticky" from the lacquer-thinner.  May even require both hands to dispense the L.C.  The Glass syringe doesn't have this issue.  Too expensive to include with the Tool, the Glass option may be something to consider.   Ebay - 100ml Glass Syringe Standard Diameter Caliber Injector Laboratory 
Thanks for the info !
You've got some serious rust-chunks, there !  At the very least you should seriously consider a larger fuel filter.
......and there'll be NO KISSING on our first date !

mizztheman  - that's some serious rust coming out of your tank. Without a doubt, I'd start there. I'd suggest lining it with POR-15, which should last forever.

Dear all,

Latest report following the carb rebuild and flushing the petrol tank out which I completed yesterday. There is a couple of things to mention before I go on. The flaking rust particles in the petrol tank was only situated around the fuel sender unit and nowhere else. The filter screen around the petrol tap was spotless.

The tank was flushed with cold water and then with hot soapy water, rinsed again and then dried with a hair dryer. Inspected once again with the camera and all clear. For the purpose of testing the bike the tank was clean enough but I admit I will need to treat the tank with POR-15 or similar in the near future. Plus, I don't want to be kissing anyone's butt if the problem comes back.

If you look at the previous picture of the fuel filter you'll notice that the knurled nut is 2 to 3mm away from the plastic body that houses the filter mesh. Effectively, it was allowing fuel to by-pass the filter directly into the carbs. This has now been cleaned and reassembled correctly so there is no gap between the knurled nut and plastic body. Its worth noting that it was fitted directly out the box so it's always worth checking things are assembled correctly before fitting.

After fitting the carbs back on the bike last night I adjusted the fast idle, tick over and synchronised the carbs this is what I found.
1. Bike would tick over at 950 rpm without eventually stalling.
2. When revving the engine the revs would return directly to 950 rpm without hanging around 3000rpm and slowly returning to 950 rpm.
3. Bike revs cleanly with no misfires.

Looks like I've cured the problem and cant wait until the following morning to try it out.

However, the following morning although the bike is the same as the night before with regard to points 1,2,& 3, when I drove the bike away from the house and put the engine under load there is a slight hesitation and misfire between 1500 and 2500 rpm. Above this the bike is faultless except at a constant speed of 60/65mph which, is about 3500rpm. it feels as though one of the cylinders has the occasional misfire. it's hardly noticeable but I know its there. when cruising at speeds above or below this or under moderate or hard acceleration the bike doesn't miss a beat.

The other thing that has developed, that wasn't there before, is on the overrun the bike has started to backfire. When I stripped the carbs down everything was laid out in order and put back exactly how they came apart. When riding out of Llangollen today there is a long section of road, with long twisting bends, which is downhill. The above problems seemed to disappear, with the exception of the backfire on overrun, and I only conclude that this may have happened due to the engine being under less load although I could have been imagining it.

The other thing that happened today is the oil light came on after about 40 miles. My first reaction was to pull over and stop the engine. On further investigation there was no sign of any leaks and the wiring to the oil sender unit was connected. I restarted the bike and the oil light went out. I covered about 120 miles today and the problem never reoccurred.

Overall the bike is performing far better than before I cleaned and adjusted the carbs but the niggles are still there. I suppose I'll have to live with it in the short term as I'm back in Spain next week and wont get a chance to look at until after I return. I did check both filters which, are spotless, and took off one of the float bowls with no sign of any particles or residue.

If anybody has any ideas I'd love to hear your suggestions as to what this might be.

Kind Regards

Martin

under load there is a slight hesitation and misfire between 1500 and 2500 rpm.

This symptom is typical of one or more of some of the three "transition" ports being blocked.  The engine as you've discovered is very sensitive to these types of blockage.  By the amount of rust that has come from the corroded sending unit, it's not at all surprising.
Regarding your fuel filter -  I thought I'd try the same one some time ago, and it never made it onto the bike. nuff said ! 
Again - I'll suggest you buy a larger one from an automotive store. In your case a clear/translucent plastic body with a paper filter element. It won't cure your existing issue but will help in lessening the chance of errant debris making it to the carbs and creating more problems.

To be clear - Did you install  "Carb-kits". (Recently?)  

I agree with Scotch, you're hesitation at 1500 - 2000 is at the point of transition between the low speed / idle circuit and the main jet circuit. Could be a partially blocked transitition port but don't rule out the carburetor piston valves. If they are a little bit sticky, they won't lift in a timely manner. Also note that some of the aftermarket rebuild kits seemed to show up with carburetor piston springs and they should never be in the kz1300 carbs. Some guys put them in to assist lowering the piston. It's a stupid thing that's cropped up twice in the last 3 years as I remember. You should be able to raise the carb pistons with a slight pressure from your finger and they should fall under gravity.

You also noted backfiring on overrun (deacceleration) That indicative of sticking/stuck coaster enrichening valves located under that small cylindrical cover near the top on the left side of the carbs. There's a brass piston attached to a diaphram and the brass piston quite often will stick in the bore in the carb body. Remove the cover and be careful because there's a spring under the cover that will shoot across the shop. Then carefully remove the diaphram with the brass piston. I like to clean up the brass piston with "Autosol" which is a polishing compund for metal. I also like to clean the bore in the side of the carb body with a Q tip and Autosol. When the brass is shiny and the bore has been wiped for a few minutes, clean everything up with lacquer thinner and reassemble. That should rectify the backfiring on deacceleration.

Last but not least, these carbs for whatever reason are extremely sensitive to debris. Most of the inline fuel filters being sold for gravity fed small engine fuel systems are typically filtering at 70-80 microns. There are a number of "better filters" available which filter down in between 10-30 microns and I really think we need to pay attention to what we buy and install on these bikes. The only downside to using the finer filters is that they may plug up earlier and could leave you sitting on the side of the road if they plug up. It's a double edged sword. Too coarse a filter and you take the chance of blocking the transition ports (which are the smallest ports in the carb) or run super fine filters and have all the debris getting trapped in the filter and take the chance of no fuel flow. I think you need to pay attention to what the micron filtering range you buy and be the judge on what you feel is appropriate. I like the 20-30 micron range and will monitor the filter. And I certainly would be shy about carrying a spare fuel filter with me for change out if stuck on the side of the road. I have pulled filters off and blown them clear with my mouth and reinstalled but then I had to taste gasoline for the next 6 hours. Where's Tim Hortons when you need one.

Kawboys reference and explanation regarding the enrichment diaphragms/pistons is valid ! I presumed that these would have received the same cleaning attention as the rest of the carbs. and parts ?
I'm considering an other situation that may mimicking a "defective" enrichment assembly and am still thinking this through.
Still curious and need to know if you replaced the choke plungers?