life span of a k5 motor

[powerfreak88]

Hi everyone! This is my first post I have been lurking in the shadows for quite some time so i figured i should pop in and show my appreciation to the site. This site is awesome!! Gobs of usefull info to be gained here. I'm the proud owner of a '93 K5 and have had it about 3 years now. It is very clean and in great condition. Bike starts in 1 or 2 kicks, cold or hot and runs very crisp from bottom to top end. Runs strong and pulls like a freight train. It is my only bike so it has been ridden alot since i bought it. So here is my question. How long should i be able to go before i need to rebuild the engine? I clean the air filter every couple rides and last time i checked compression it was almost 170 psi. I'm pretty sure it has a stock piston but not positive as I have never had it apart, but i looked up the exhaust port and it looks to be a cast piston(not sure though, how do you tell cast from forged?). I want to do the top end but money is very tight right now and is probably going to be that way for a while. Should it be ok as long as it maintains good compression? I've heard of cast pistons blowing apart and thats what worries me. Any input is greatly appreciated. Here is my setup in case anyone is wondering.
fmf gnarley(woods)
powercore silencer
twin air filter
boyesen power reeds w/stock cage
boyesen super bowl
power now
DP clutch kit w/steel drive plates
engine is stock (i think?)
P.S.  sorry if this topic has already been covered but i don't remember ever reading it. Thanks in advance
LET'S ALL STRIVE TO KEEP THE K5's ALIVE    

[Suva]

My brother's K5 is just now going through its 2nd rebuild (2003 model?) after being raced hair & hound and hair scrambles and hard woods riding.  Not currently his primary bike, but he's put more hours  on it then a large portion of bikes see in the same time-span.  K5s are tough if you maintain it properly 

[oic0]

Just think of billet aluminum vs cast aluminum. Cast looks sort of dull, forged is shiny (though probably scuffed to  being a bit dull) and probably has horizontal machining marks on it.

When you make your power with CCs instead of just running the piss out of a smaller motor, you get a much more reliable motor.

[mxaniac]

Obviously most of the wear comes from hours not calendar days.  Our weather only allows us to ride for 6 months per year.  In that span when we raced and practiced constantly I needed 2 or 3 pistons per year for the CR85, 2 per year for the CR125, and 1 per year on the CR250 to avoid power loss.  If you ride a lot I would project that out to mean at least every other year on the KX500.

[powerfreak88]

thanks for the input. Hopefully it
makes it through this summer without grenading lol lol.