Piston change hours YZ 125

Burger745
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Whitinsville, MA, USA

My son has a 2024 YZ 125. We run VP C-12/motul 800 32:1. We run strictly MX. The bike has FMF pipe:silencer, GYTR Jet kit and bike was dyno tuned when new. Kid rides on the pipe as a quick B- rider. Just hit 20 hours. Just wondering how often other racers are doing top ends on these bikes. Have VHM Head with race fuel specific dome and VHM Get CDI I’m going to install with new top end. Looking for a baseline for piston change. Thanks

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Factor E
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So Cal, CA, USA
9/24/2024 5:47am Edited Date/Time 9/24/2024 5:48am
Whats your budget? How quick did you put 20 hrs on? Good to change around 30hr mark
1
Burger745
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9/24/2024 6:14am

That’s kind of what I was thinking for hours. I had some other guys telling me 15 hours. If that was the case, I’d be changing out a piston every three weeks.

Alex814
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9/25/2024 7:25am

I've heard of OEM cast pistons breaking early, so I changed to forged and am replacing around 25-30 hours (once per year for me).

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Falcon
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Menifee, CA, USA
10/1/2024 3:48pm

If cost is an issue, you can probably get away with a new ring and re-run the old piston for one change. Clean the carbon off the top and make sure it still measures within tolerance. 

1

The Shop

Burger745
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10/1/2024 4:15pm
74941646952  6913FAD6-547C-4C72-94DD-0AF7EB27C36074941647882  B08F7C58-291A-43B7-8449-0C1C264DFC9F.jpeg?VersionId=KU
Burger745
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10/1/2024 4:17pm

This is at 24.4 hours. Definitely needed changing as the sides were starting to get polished and you were not able to see the machining marks.

Burger745
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10/1/2024 4:54pm
IMG 8361 1
Burger745
Posts
90
Joined
12/16/2018
Location
Whitinsville, MA, USA
10/1/2024 4:57pm

New head with special order race fuel dome, top end and VHM CDI installed. Bike should rip!

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