How often do you re-build

You've logged your hours or kept a close eye to the hour meter and its time for a top-end, how often do you re-build?

If it's a race bike I could see doing it ever two seasons or so. Mine isn't so I'm not gonna rebuild it until there's a reason to. I take good care of mine so it should last a long time without a rebuild.

I wait until the shim size on any valve is reduced more than .2mm below the original. In the case of our YZ250F, that took 4 years.

after four years how did the cylinder, piston and rings hold up.

it really all depends on how the bike is ridden. if it is just a bike you go and play around on every now and then then many be ever other season but if you race the hell out of it i would check up on it ever season.

I still have the original valves in my 01 and it still runs great. The bike was shimmed one time by the dealer awhile back but still has much more to go (i dont remember how much but i know it was nowhere near .2mm). The bike isnt raced but is ridden hard when it gets to the track.

Mine has about 70 hours on it and still starts like its new

I'm in the process of doing my top end and valves for the first time in four years...'01 YZ426..I have raced this particular bike in MX at least 25 times..exhaust valves were within tolerance..one intake valve was in, the other two were a little tight...reshimming, and replacing piston, rings, cam chain..etc...

I'm in the process of doing my top end and valves for the first time in four years...'01 YZ426..I have raced this particular bike in MX at least 25 times..exhaust valves were within tolerance..one intake valve was in, the other two were a little tight...reshimming, and replacing piston, rings, cam chain..etc...

make sure you replace the timing chain and all the valve springs.....just good preventive maintenence and these are't that expensive.

My bike was new out of the box june 2004 and I re-built it in November after five months of pounding, I just did the piston, rings, clips, pin and gaskets. This winter I'm going to do it all, valves cam chain etc.. I ride at least twice a week for 4+ hours a ride, i figured it would be a good idea. I wish I did my cam chain...cheap reassurance.

after four years how did the cylinder, piston and rings hold up.
I replaced the rings and reused the original piston. I saw no wear or other reason not to use the piston. The bore did show a slight "shadow" at the top of the top ring travel, but it wasn't measurable, and disapperared in a single pass with a ball hone. It broke in in 3 hours to the point where it no longer uses any oil.

I will probably replace the cylinder and piston sometime later in the year, simply because it has been there so long.

When I do my rebuild, in a year or two minimum, I'm going with a big bore kit. Is there anything to replace in the bottom end?

check your crank and bearing, you should have no vertical play on the crank bearing, thats all I checked when it was open. I don't know much about the bottom end.

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