A few questions regarding YZ125

[beaner]

I've been looking for a late model YZ125 to build a woods bike. They're lighter, and have a shorter wheelbase than any other full size bikes, handle well, and parts are plentiful.

In my research, and looking at ads I see a lot of 1-3 year old bikes with not many hours, but new cranks, new barrels, or complete rebuilds. We're talking bikes raced at the local junior/novice level. On another forum there's a YZ section, and a guy who does a lot of work on them who says at 60 hrs it's time for a complete tear down and rebuild. Other guys replacing or replating barrels at less than 100 hours.

My (CR150) Husky has over 100 racing hours, is on only the second piston, and on the big bore 165's, guys are getting 200 hours on a top end only and I've seen Husky 2 strokes with 400-500 hrs on them with not much work.

Are these YZ's really that lightly built, or are people doing a lot of unnecessary work?
I'm not that concerned (personally)  because I set my woods bikes up for strong low end power and rarely wring them out

I do remember asking the Husky dealer when I bought mine about replacing top ends with regularity and he said no, It's not a Japanese bike 

[eprovenzano]

My son had a 99 YZ125... When we purchased it, the top end had 20 hours of racing on it.  He road it for several years on both woods and track (no racing).  As time passed the took over my 250 and I sold the 125 to a buddy.  He wad beat the piss out of that bike... little to no maintenance.  He rode it for years knowing it needed a top end, but continued to ride it.  the water pump seal failed and he limped home for the woods with an overheating bike.  He parked it and life got in the way... it sat for 18 months, after me prodding him to get it out and fix it, he pulled it out of his basement, kicked it 5 time it fired up and he rode it onto my trailer. 

When we tore it down, the internals were in excellent shape...  Other then being filthy dirty, everything was pretty good.  Yes the water pump seal was bad, the piston was way past due, but the cylinder was in excellent condition (I guess all the blow-by helped coat the cylinder).  The rod was tight, and the crank bearings had no play that I could tell.  We put in a new top end, new gaskets, new water pump and seals and she still live today..

I guess the moral to my long winded story is yes a 125 needs a little more top end maintenance, but I think the crazy maintenance routines of some riders are a bit much.  Some seem to enjoy wrenching more then they do riding.  You should be able to go 100 hours on a top end, and 250 - 300 hours before thinking there's a bottom end issue.   To answer your question "Are these YZ's really that lightly built, or are people doing a lot of unnecessary work?"  I feel they are doing unnecessary work.