TOPIC:

I don't have an interesting repair story to tell while waiting for the snow to melt, so I pose a question instead.

I thought one advantage of the use of shims was that valve change intervals are longer than engines that have rocker arms.  Yet, 5000 klicks is not very; I'm past that and can tell.  Does anyone know what is with the engine that requires such frequent valve check/adjustments?

Lots of info to decipher here.
first, we have to realize that the KZ1300/zn1300 were born and thrived in a 10 year window. 1979-1988? and during that time, a lot of development happened in engine valves due to the change in gasoline requirements to meet emission standards.
Tetraethyl lead was added to gasoline for the sole purpose of lubricating valves and because of that the quality of the valve seat faces and the valve seal faces was not as much of a concern. As soon as we removed lead from the fuel all kinds of issues happened at the valve sealing faces that needed to be addressed with better materials. Even cast iron cylinder heads had to be modified to accept hardened valve seats.
Valve seat inserts for aluminum cylinder heads way back in the beginning were made from high carbon steel or chrome moly. When unleaded gas came into effect (and by law, that happened in 1996 in the U.S.A. ) Valve seats had to be upgraded to a much more tolerant material to high heat. Sintered metal seats came into play. The ability to create a matrix of variable compounds and create a material that could not be created by foundry practices made a huge difference in the wear capabilities of valve seats. In this day and age, sintered metal valve seats is the go to for replacement seats. Beryllium seats are used with titanium valves but that's another kettle of fish.
Valves have also come a long way since the late 70's- 80's and able to withstand the hotter environment. And of course, you get what you pay for. What's available for the KZ1300 is probably the good old Chinese valves materials of the 1970's 1980's and the only way you're going to get better valves would be to custom order valves from companies like Vesrah, Mahle, Crower etc. My go to here would be either Ferrea or Supertech Performance and either option is not cheap.

Then there's the human variable. The initial machining fitment of the valve seat faces and the valve faces is a critical aspect to how long the valves will last. Not enough attention is paid to the information provided requiring seal face widths and location on the face of the valve. If the seat isn't wide enough or is placed to far up the valve, then cooling of the valve face will not be adequate and premature wear will happen.
That's just the tip of what I know about valves but it may give you an idea as to how complicated the subject is.  I'm in the process of replacing my valve seats in the cylinder head and as soon as time allows, I'll get back in to it. The biggest problem I have is that a direct replacement seats were never made available and the cylinder head doesn't have enough material in the web between the intake and exhaust to allow machining of the head to accept the next size up valve seats so I have bought the next size up seats and Ill have to machine them down to fit the head and keep a .005" interference fit. Then heat the head to 300F and cool the seats with N2 and install. Not a job for the average guy.

 The initial machining fitment of the valve seat faces and the valve faces is a critical aspect to how long the valves will last. Not enough attention is paid to the information provided requiring seal face widths and location on the face of the valve. If the seat isn't wide enough or is placed to far up the valve, then cooling of the valve face will not be adequate and premature wear will happen.

And again I feel compelled to say :  This is why my Cyl.-head ( also pistons & cly's) went to a machine-shop and why; when the machinist said I should get new valves - I did.  If the journeyman machinist didn't have confidence in re-grinding my originals - Where would that have left me if I were trying to do this work myself ?   The Vesrahs were expensive but my mandate was simple:  "Do it correctly the first time" !  .......... with the exception of the piece-o-shit "Italianmetal"  head-gasket !      (Ya......another  "dig" and a reminder for others!)

Would a lead substitute reduce the need for as many valve adjustments/checks? 

Whiskey1300 wrote: Would a lead substitute reduce the need for as many valve adjustments/checks? 

This is a take off from a wikipedia discussion on leaded gasoline   

Valve Wear Preventive -  Tetraethyllead helps cool intake valves and is an excellent buffer against micro welds forming between exhaust valves and their seats  Once these valves reopen, the micro welds pull apart and abrade the valves and seats, leading to valve recession. When TEL began to be phased out, the automotive industry began specifying hardened valve seats and upgraded materials which allow for high wear resistance without requiring lead.

So, yes lead additive would help but it's a band aid as opposed to a cure. Really, if you want to do it right, replace the valves with high quality valves and replace the valve seats. Now Scotch will tell you that you can get 100,000 kilometers out of a valve job before refacing, so why not just live with the issue? 

The biggest problem is that little attention is paid to is the carb mixture jetting. Most people just live with how the engine is running and not make any adjustments to correct a bad running engine. Ultimately, if you tune your carbs for a brownish color sparkplug, you should be just fine. The trick is to run lean enough to achieve good fuel mileage and rich enough to keep the valves cool. Light brown sparkplugs is the happy place. white plugs are running hot and you're just asking for trouble. Most automobiles produced in the last 20 years run sparkplugs white hot and they can only do this with fuel injection managed with a closed loop system that continuously monitors the O2 and adjusts the fuel ratio based on a fuel map, engine temp, air temp, throttle position  + the O2. So they are able to run extremely lean all the time BUT they also have components that can run hot all the time. 

The Zn1300 fuel injection runs in open loop which means it follows a fuel map based on air temp, engine temp, throttle position and RPM's and the fuel map is conservative to the rich side because it doesn't monitor O2 so in reality it's not much better than a well tuned carb

So, what is achievable ?? As per the topic  Defeating the Enemy  Scotch has been able to achieve
52.84 MPG  @  100 KPH (max).    .6214  Kilometers per mile &  4.54 L = 1 Imp. Gal.   Used all 3 decimal places 

     This is the 4th time for this mileage so now have a solid base-line.
Look out "55" .....Next year I'm coming for you ! 

    ( Double platinum plugs and Gold Plated Coil and Spark-plug connectors ! )  

 So, if you're not anywhere close to 50 MPG (imperial) You have work to do. If Scotch can run lean enough to achieve 52.84 MPG and get 100,000 Km out of a valve job and only have to reface the valves and seats without replacement, then you too should be able to tune to that level.

A small correction?    I replaced all the valves.  None burned or damaged in anyway but was the machinists recommendation because he was concerned that reground valves and seats would create a shimming issue.   ie:  Too close to or even tighter then the thinnest available  shim - 2.0mm. 

And to reiterate regarding my mileage.  Strict 100KPH limit and multiple identical rides for comparisons..
Stock NGK spark plugs, a GM  6-pack ignition coil and typical silicone jacketed wire wound carbon-core plug leads 

• Modified pilot needles - Polished to a point with a new arbitrary setting of 2 turns.  More sensitive then the stock tip,  the adjustment range for the Color Tune is now approx. +/- 1/4  turn which makes mixture adjustment far more accurate.
• Enricher mod (Disabled)
• Precisely sync'd 
• minor adjustment to Ign.-timing.
• New Brass throughout.  Stock jetting !