Top End Rebuild on 450's - # hours?

[Spokes574]

I have a CRF450R Y05.
I had a piston put in 37hrs ago.
The manual says to replace piston ~22hrs.
I have read in magazines about 450's taken apart at 75hrs and they say the piston and compression is still good.
I do not have a way to check compression and change the oil every 2-3 rides with synthetic. I changed it in the past at 50hrs and only noticed less vibration and smoother roll-on.

Whats the verdict for the normal population to change
a piston in the 450's - after so many hours?

Cost of a high compression piston is cheap ~$169
its the labor to put in $250+ .

Thanks,
Spokes574

 

[2 strokes for life]

I would say buy a compression tester and check when the manuel says to. I think most people i ride with get about 50 hours on a piston.

 

[krosser]

At least. I do my sons 250 at that and it still has life in it. Just in case.

 

[Spokes574]

Based from what I am hearing from folks ~50hrs is the sweet spot for changing the piston. I am at 44hr now, so I will change it at the end of January, by that time I should be in the high 50's Thanks,

Spokes574

 

[cthowards]

On my 2005 CRF450R I changed the piston and rings (as well as valves, springs, etc.) at the 80 hour mark (two seasons of riding). The cylinder was fine and all the parts appeared to be in remarkable good condition. You can see some pictures I posted last year in my gallery.

Good luck with your rebuild.

 

[truespode]

Here are some pics of my 2003 YZ250F when I did the top end at 80 hours.

Things were in real good shape.

http://truespode.net/temp/topend/

Ivan

 

[Rich Rohrich]

Ivan - We need to get you a decent camera. :)

 

[whenfoxforks-ruled]

How long you can milk a rebuild out to is a fine line between good maintenance, manufactured defects and how it is rode. With maintenance and good parts there are engines that get rebuilt more than recomended by the oem. More relaxed usage and yes 100 hours is not uncommon. As long as you understand what can happen! Spokes statement about his bike rolls on better and less vibration is everything in a nutshell! Your bottom end power and vibration go before a compression gauge will tell you? Maybe. That short skirted piston starts rocking in the bore, not good! Valves getting past 3 shim sizes or rods snapping is still the worst.

 

[truespode]

Ivan - We need to get you a decent camera. :)

LOL!

You have told me that before... one day I'll listen.

One day :)

Ivan

 

[Rotorranch]

I try to do mine about 2 hours before it blows up. :rotfl:

Rotor

 

[Rouse5369]

what special tools are required? besides a tourqe wrench? tahnks for the inf in advance