Change your yz250 piston!

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10/1/2016 11:46 AM

I usually go 50-75 hours on a yz piston without any issues because I'm a jetting, air filter and maintenance freak. This time in my 2016 I decided to stretch to 100 and see what happened..... Holy hell I'm lucky! The crank and cylinder are in great shape though.

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10/1/2016 12:07 PM

The stock pistons are great, but it is highly advised not to go past 50hrs because of the potential for it to crack in the window. Glad you got it when you did!

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10/1/2016 12:24 PM

i go 30 hrs yamaha parts are cheap

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10/1/2016 12:36 PM

exactly happen to me on a rm250 2007 whit a prox piston that had 70h on it

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10/1/2016 1:03 PM

Guilty of going to far on one in the past. Son was on a yz85 and just about Reay to move up to a supermini. Knew it was way passed time for a top end but couldn't justify the cost when he was so close to moving up.

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10/1/2016 3:20 PM

At about 2 hrs & 150.00, why the hell would you not just change it out every 30-40 hrs? If that thing Lets go at full tilt, you looking at a lot more $. I had 4 YZ 250"s, top ends every 30 -40 hrs, never an issue with cranks, cylinders or Pistons.....transmissions were a different story!

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10/1/2016 3:27 PM

Scary! I found one like that in a YZ125 years ago.

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10/1/2016 9:00 PM

sandman768 wrote:

At about 2 hrs & 150.00, why the hell would you not just change it out every 30-40 hrs? If that thing Lets go at full tilt, you looking at a lot more $. I had 4 YZ 250"s, top ends every 30 -40 hrs, never an issue with cranks, cylinders or Pistons.....transmissions were a different story!

This is my 4th yz and I currently have two (2016 and 2002). It was more of a science experiment, albeit a stupid one. I'll go back to 50 hours from here on out. Here's another tip for the smoker crowd.... Add an ounce of seafoam to every gallon of gas and look how clean the power valve and motor will be when you work on it. Old timer told me to give it a shot and I was amazed. No baked on goo and the stuff that was there wiped right off.

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10/2/2016 4:01 PM

sandman768 wrote:

At about 2 hrs & 150.00, why the hell would you not just change it out every 30-40 hrs? If that thing Lets go at full tilt, you looking at a lot more $. I had 4 YZ 250"s, top ends every 30 -40 hrs, never an issue with cranks, cylinders or Pistons.....transmissions were a different story!

Unfortunately, we agree with Sandman's opinion on the YZ250 transmissions.
We have seen many, many YZ transmission failures- and not just the run of the mill worn out engagement dog.
We have seen many instances of broken off gear teeth which then got wedged between the shafts, and several cases of a gear shattering into pieces which then wiped out the cases- even on very low hour bikes. This points to a fundamental metallurgy or heat treatment problem. Combine this with a weakly supported 4th gear, and the YZ gearboxes are a real Achille's heel.
They shift well, but gearbox durability is not a YZ strong point to put it mildly.

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10/5/2016 12:46 PM

I had the same problem on my YZ at 20 hrs on a stock piston. The skirt cracked off and locked the motor up. I switched to the wiseco GP style piston and I cant get 25hrs. That is with VP C12 and maxima mixed at 40:1 with Redline super lightweight oil.

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10/8/2016 6:51 PM

30 hours.

Top ends are cheap and its only 2 hours I would have just wasted looking at smut online anyways. 100 hours?? No way. Even 50 is a lot to me. Theres a reason the owners manual says 15 hours and its not because they were designed to last 100.

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10/9/2016 8:08 PM

Rockinar wrote:

30 hours.

Top ends are cheap and its only 2 hours I would have just wasted looking at smut online anyways. 100 hours?? No way. Even 50 is a lot to me. Theres a reason the owners manual says 15 hours and its not because they were designed to last 100.

Yeah but now you know for a fact lol. Science experiment my friend.... Science experiment

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