Mechanically
The pistons got a bad reputation so I went over to TZ almost from day one so have no experience of failure. I do know some that raced on stock pistons and they did let go. I do suspect that some of that might have been down to not getting an engine warm properly.
If you are ham fisted with the assembly of the barrels and heads you can warp the head or crack a barrel. Not had one fail but as I shorten the barrel by about 2mm which weakens them at the point they break I now get a plate weld across the back of the barrel. There is so little metal on the barrels that they flex which allows the base gasket to push out. To prevent this you need to dot punch the cases or barrels (and I use a bit of Yammy Bond) to give the gasket something to bite against.
If your crank isn't trued up properly, especially generator end, then they can crack the left side of the crankcase.
I know people have had problems with detonation but that is running too high a compression ratio - I avoid that as it stops the engine over reving. You also can get a bit of detonation in the gap between the head and barrel where the head gasket sits. Can avoid this by using Honda three bond when assembling - this squeezes into the gap and seems to stop the detonation damage. On fuel I run 50/50 just to be safe - compression is so low that I could run 97/98 octance pump fuel but why risk it.
Engines are pretty reliable. In 8 seasons racing the only problems I have had were me being sloppy in preparation. Two seizures - one didn't have enough fuel in and with the tap on the left you starve the engine when going round Gerrards. The other forgot to drill the oil holes in the pistons
One cracked crankcase - threw a crank in with out checking it
Broke a bunch of exhausts when I fitted long silencers - for looks we don't run the rear support - the long silencer changed the mechanical resonant length of the pipe and they kept fracturing. Gone back to short TZ cans and no problem.
Tuning wise - though there was a F3 kit all the KR stuff is unobtainable. So you need to improvise and make do the best you can.
The KR runs stock ignition, standard road expansions, standard Carbs (albeit KR-1R) tuning is a bit of porting and heads reprofiled to match the TZ pistons which have a 120mm radius dome as opposed to stock 150mm radius - so in that respect Kawasaki got the basic package pretty much spot on.
The challenge I have is making more power as with what I have got I reckon I have pretty much maxed out. I have a few alternative head profiles to try and I am presently revising the profile of the boost port but that is about it with out going to different expansions and ignition next.
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