After reading the thread about valve lash and what is involved with adjusting the valves, I have a question for those more knowledgeable than I.
As I understand it.
The reason the lash gets tighter with this valve train system is mainly due to valve seat wear causing the valve to get progressively deeper in the seat and reducing lash. Is this correct? If so, I remember right after the lead was removed from fuel those of us with older cars used a lead replacement fuel additive to help protect valve faces and seats. Doesn't Kawasaki use hardened seats in the heads? If not, would it help extend the seat life by adding this to the fuel?
#1, Mostly correct. It is both valve & seat wear.
IMHO, Kawasaki probably purposely used softer than I'd have preferred Intake Seats. The Exhaust seats are harder, in part to deal with the extra heat.
IMO, the softer intake seats will wear quickly enough after an Improper Air Filter Servicing to become a hard or Non-starter, then a wise mechanic can chastise the errant owner for his error.
Perform a air box cleaning, maybe find and repair a Burn Hole in the bottom of the air box, install a properly oiled air filter, perform a valve tappet adjustment & get another 10,000 - 50,000 miles of use out of the engine before requiring a top end rebuild.
IMHO, probably not.
IME, Kawasaki does Not perform a 3 angle cut of the valve seats on their lower performance engines, Only a 2 angle cut. This usually leaves Too Wide of seating surface. Too wide of contact patch reduces the psi of that contact. This reduction of seating pressure allows more seepage than desired, which causes some erosion of its own.
But it won't hurt to try a lead substitute, if you desire.
I had to perform a top-end job on my own bike because it acquired a burn hole in the air box Way Back when. Caused by a failed mid-pipe exhaust gasket, which I think Kawasaki had even up-graded before my failure date, IIRC. But failure date was beyond warranty period.
Anyways I eventually ran out of available valve shim sizes by 33,590 miles and was using 16oz oil per 400 miles. Once an engine has been 'Dusted' the wear continues, because the grit is embedded into all of the affected surfaces.
Anyways, I performed a 3 way re-cut of the valve seats to near the minimum 0.8mm / 0.032inches
with my Neway cutters. Then lapped the new valves in.
My engine has since run 49,503 miles since that work and I have only changed down 1 size shim on each valve, so far.