2011 YZ450 with 119 hrs. Time for new piston?

I'm debating just doing preventative maintenance on my bike I use in the winter with a Timbersled snow bike kit.. It's still running strong with the stock motor and 119 hrs but am I playing with fire trying to put another 50 to 60 hrs on it?

If a new piston and rings are to be done, does the cylinder need work as well? I understand that depends on if the cylinder shows wear but is it mandatory if it doesn't?

Just checked the valves and they are all in spec, bike starts in one or two kicks.

I'd like to know what other guys recommend that have ran bikes with higher hours.

Thank you,

One never really knows without looking.  My '06 went to right at 300 hours on the original top (and that was just a little bit longer than it should have gone, but no problem).  The piston was worn out, but the bore was fine.  In a case like that, the bore needs to be deglazed, and that's best done with a "brush" or "spring/ball" hone.

Out of curiousity would anything need to be done to the valves at this point if they checked out good?

How many times have you had to reshim them? How much did they move?

One never really knows without looking.  My '06 went to right at 300 hours on the original top (and that was just a little bit longer than it should have gone, but no problem).  The piston was worn out, but the bore was fine.  In a case like that, the bore needs to be deglazed, and that's best done with a "brush" or "spring/ball" hone.

curious what type of riding and skill level? and type of oil used?thats some serious hours to go on a piston....im assuming a good synthetic and some short intervals for it to last hat long. thanks.

curious what type of riding and skill level? and type of oil used?thats some serious hours to go on a piston....im assuming a good synthetic and some short intervals for it to last hat long. thanks.

Expert, but an older rider.  10-15% MX, with the rest being recreational/"training" and desert racing.  Amsoil MCF (MCV in summer) or Mobil 1 Racing 4T (V-Twin in summer).  Original piston changed out in '13 after 5 seasons of racing, plus whatever the PO did with it (mostly it sat for the first year and a half 'til I bought it).

How many times have you had to reshim them? How much did they move?

I have not had to reshim them. It has never been raced, it runs great. It has 170 hrs on it.

Leak down test

I have not had to reshim them. It has never been raced, it runs great. It has 170 hrs on it.

 

If the clearance is in spec, and they pass a fluid leak test, they need nothing at the moment.

What is the leak test, how is it done?

Expert, but an older rider.  10-15% MX, with the rest being recreational/"training" and desert racing.  Amsoil MCF (MCV in summer) or Mobil 1 Racing 4T (V-Twin in summer).  Original piston changed out in '13 after 5 seasons of racing, plus whatever the PO did with it (mostly it sat for the first year and a half 'til I bought it).

that's awesome.....

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