Rebuild miles?

Probably one of the stoutest motors ever, but but pistons are still susceptible to metal fatigue overtime. I would put pistons in it. Not that guys certainly haven’t gone to 10k before, probably even longer.

what is the compression at??
, as I never just go off miles or hours, I base rebuilds on a few other things besides miles and hours, like
starting with a compression test, and then, evaluate t how hard a motor was used or abused, and what fluids were used along its life!
big difference iMO in wear and tear on a motor being run at max or worked hard all the time, as to one that was run a little more mild !
how the operator also, runs things from cold start up , some folks start and hammer away, some let things warm up first or go easy first few miles,
all adds up to wear and tear IMO!

SO, IMO< there is no real set rule on WHEN to rebuild,
start with compression test and go from there !~

That’s 100% correct, but since he’s at 8k, that means it’s been taken care of/warmed up/etc. or it wouldn’t have made it that far.
I’ve found more than one motor to have excellent compression (as new), but noticed that the exhaust side skirt was cracked (or even half missing) while servicing the exhaust valves.

My buddy's 2007 F1000 locked up solid around 4,500 miles iirc. Torn intake boot. Happened at 100 mph.

Totally understandable with use and maintenance plays a big role. We maintain the sleds impeccably with servicing and good oil, put new intake boots as a maintenance thing and tear it apart every year and clean it. secondary clutch is getting worn, just haven't had to touch engine yet!

I would order new Ac pistons, base gasket and head orings now. Incase it takes a bit to get them.