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yz250 when to do your topend?


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I was just checking to see how often you replace you topend on your 250. I've had my 01' for 4 years about for years, I'm positive that the bike hasn't had a rebuild in the last 6 years. I mostly ride single track trails about 1-2 times a month and I've raced about 6 times on the mx track. I'm an intermediate trail rider and a novice mx rider. The bike still runs very strong with good compression. I maintain the bike well with oil changes and airfilter cleaning. The only thing that seems to have changed a bit this year with the bike is the jetting doesn't seem to be as crisp, maybe it's because of the cooler spring temperatures though.

I was just wondering am I taking any chances of doing serious damage rather than just rebuilding it now? I used to have a 99' yz125 that seemed like I rebuilt 3 times in the 2 years I owned it.

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50-60 hours for me too. Compression tests don't always tell you the whole story, just that the rings are sealing. The piston could be rocking and ready to shatter a skirt, but the compression test might not show that. I had a piston with just over 50 hours on it, put up 247 psi on my compression gauge the day I tore it down. Skirt was full of hairline cracks, a piece actually broke off when I set it on the bench.

A buddy of mine had an 01 he bought new. The bike started and ran great, and he said there's no way he was going to waste money rebuilding it when it obviously didn't need it. He thought I was crazy for putting a top end in my KDX each winter.

Anyway, in 06 it shattered the piston, destroyed the cylinder, and twisted the crank when the flailing rod hit something (port? can't remember) and stopped things right now. By not "wasting" money on a $100 top end he was able to pay over $1K to get it all fixed, and then had to sell it to repay the guy that rebuilt it.

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Buy my new forged top end kit for $120 shipped. If you go forged you won't have to worry about piston shatter.

For piece of mind, change if before this season starts whether you buy my kit or not.

Agreed, peace of mind goes a long way.

Nice signature Shrub.....we may be talking. I have plans.

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I race mx and do mine at 30 hrs so you should have no problem gettin 60-70+ hrs out of your top end... although I would still do it at the beginning of every season just for peace of mind. Might be overkill but Id rather explain why I decided to spend $120-$130 for a top end than explain why Im spending big bucks on a top and bottom end rebuild...

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I was just checking to see how often you replace you topend on your 250. I've had my 01' for 4 years about for years, I'm positive that the bike hasn't had a rebuild in the last 6 years. I mostly ride single track trails about 1-2 times a month and I've raced about 6 times on the mx track. I'm an intermediate trail rider and a novice mx rider. The bike still runs very strong with good compression. I maintain the bike well with oil changes and airfilter cleaning. The only thing that seems to have changed a bit this year with the bike is the jetting doesn't seem to be as crisp, maybe it's because of the cooler spring temperatures though.

I was just wondering am I taking any chances of doing serious damage rather than just rebuilding it now? I used to have a 99' yz125 that seemed like I rebuilt 3 times in the 2 years I owned it.

buy an aftermarket piston kit. i put a wiseco in my old 465 a year ago, all im giving her now is rings. much cheaper. it would be a silly waste to junk a perfect piston,im gonna do the same next year. this is ok if your not a pro, those guys demolish engines.

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were talking several summers of ridind (like 4+) on my top end. compresion is 163 lbs which looks good to me. i run my bike a little on the rich side and clean air filter frequently and properly mix 40:1 with amsoil. ill be doing a new top end this winter just for preventive maintenance. i dont race, but by no means am i a trail riding queen. 👍

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