sounds like your dealer is a crackpot, how many people he services have 50 hrs. on their quad? There was a post a couple of weeks ago that said you have to rebuild a yfz every 25 hrs. My grandma might get 500 hrs., where as bill ballance requires the utmost in performance, and might rebuid every other race or so. We all ride differently, and also expect different things from our quads, me I'm looking at getting 2-3yrs. on a top-end, and that is acceptable to me.

 

Rappys, probably not
Shees, I'd say yes (if you want to avoid the possibility of trouble)

Why is this?
Because the YFZ is a high revving 4-stroke (10,500 RPMS), highly strung motor, with a high compression piston (11.9:1) and extremely short skirt. This is why it performs so well.

You can probably push them longer, but I have read many reports from YFZ forums where the piston let go at approx 150 hours or so, and took out a lot of motor with it (resulting in 2000 bucks or so worth of damage).

Most ave riders don't put 100 hours on there machine very quickly unless they are riding every weekend. the 100 hours is actualy ride time, not counting the time spent with the machine off BS'ing with friends.
Say I go for a weekend trip to the dunes. I probably actually only put about 8 hours or so of actual time that the motor is running for the entire weekend (actual time that the motor is running and on the gas). So basically 12-14 full weekend trips for me would equal a rebuild. It takes me an awful long time to put that many weekends on my quad.

Like I said, you can probably get away with a longer period, but I feel you are pushing the envelope if you do.

If not, at least pull the piston and check the measurements on it. Once it starts to wear, it is going to wear pretty fast after that.

I know guys that race quite often, and are still on the original piston and rings a year later, but I think they are pushing it, and when it goes, it goes big! (usually takes ot the head, cylinder and sometimes the crank).

To each his own, but if you have a 7000 dollar race tuned ATV, why not take proper care of it (say once every 1-2 years for the ave rider).

Get an hour meter attached, and you might be surprized at how long it actually takes to rack up 100+ hours (of actual run time).

 

i have aproximatly 1500+ miles on my yfz in one year, of hard riding a pussying it, and i havent had to rebuild mine yet, but dirt got sucked into the motor (thanks to the airboot falling off) and it still runs a lil faster than the 450r and it makes engine noise but 1500+ miles and it hasnt needed to be rebuilt

 

How are you determining that the engine does not rebuilt? Because it has'nt blew up?

 

is this true for all 2 strokes?

 

maybe the dealer ment reclearence the valves.