Yz125 powervalve

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12/19/2018 11:00 AM

Hi all, I was stripping my 03 yz125’s engine and when I shook the barrel there was a rattle noise, I opened the powervalve cover and two small little metal bars came right out! I’m not sure where they go so any help appreciated! Here’s a picture...

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12/19/2018 11:01 AM

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12/19/2018 11:02 AM

Photo
Photo
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12/19/2018 11:38 AM

Those slide into the power valves and those springs clip around them. But they are worn out looking at the groves worn into them. In fact they aren't supposed to come out at all they are supposed to be pressed into them.

The rod rotates and the springs pull on the little rods opening the power valves. Hate to say it but they are worn out.

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12/19/2018 11:41 AM

SmokinJoe439 wrote:

Those slide into the power valves and those springs clip around them. But they are worn out looking at the groves worn into them. In fact they aren't supposed to come out at all they are supposed to be pressed into them.

The rod rotates and the springs pull on the little rods opening the power valves. Hate to say it but they are worn out.

And expensive too.

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12/19/2018 11:53 AM

I just went through this exact issue. here is how I fixed it:

1) remove powervalves from cylinder
2) drill and tap an M4 hole at the outermost edge of the powervalve (surface shown in the picture above) this hole will be used for an M4 setcrew to hold the pins in. you want to drill this hole to be in-line with the movement of the powervalve. it will poke through to the pin hole which is what you want.
3) grind a small "flat section" on the worn side of the pins that fell out (this leaves the fresh surface of the pin to contact the spring. This flat section will align with the set screw.
4) tap the pin into the powervalve and make sure to align the flat section of the pin with the set screw hole you just drilled
5) red loctite set screw and tighten to hold pin in (set screw bottoms out on flat section of pin)
6) "stake" the set screw in place to prevent the pin from ever coming out again

Works great!!! And it beats buying new powervalves at $245.00 a piece. lol

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12/19/2018 11:57 AM

DynoDan22 wrote:

I just went through this exact issue. here is how I fixed it:

1) remove powervalves from cylinder
2) drill and tap an M4 hole at the outermost edge of the powervalve (surface shown in the picture above) this hole will be used for an M4 setcrew to hold the pins in. you want to drill this hole to be in-line with the movement of the powervalve. it will poke through to the pin hole which is what you want.
3) grind a small "flat section" on the worn side of the pins that fell out (this leaves the fresh surface of the pin to contact the spring. This flat section will align with the set screw.
4) tap the pin into the powervalve and make sure to align the flat section of the pin with the set screw hole you just drilled
5) red loctite set screw and tighten to hold pin in (set screw bottoms out on flat section of pin)
6) "stake" the set screw in place to prevent the pin from ever coming out again

Works great!!! And it beats buying new powervalves at $245.00 a piece. lol

Guess I’ll try this! Thanks a lot , how did you notice this issue? Did it affect bikes performance?

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12/19/2018 12:15 PM

To solve this problem the easiest way you can also buy 2 ´spring type - straigth pins (iso 8752) in the correct size and place them in your povervalve.

Have done this before, second piston change on my '15 allready came with loose pins. Placed those pins an checked it every piston change after (5x at least) and never had issues again!

https://www.kramp.com/shop-nl/nl/1014164/2874589/188452/1481640+Spanstift+6x40
Link above is from a Dutch webshop, just use it as an example.

Hope you get your Yz running smooth again!

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12/19/2018 2:42 PM

T981 wrote:

To solve this problem the easiest way you can also buy 2 ´spring type - straigth pins (iso 8752) in the correct size and place them in your povervalve.

Have done this before, second piston change on my '15 allready came with loose pins. Placed those pins an checked it every piston change after (5x at least) and never had issues again!

https://www.kramp.com/shop-nl/nl/1014164/2874589/188452/1481640+Spanstift+6x40
Link above is from a Dutch webshop, just use it as an example.

Hope you get your Yz running smooth again!

Thanks! How much do they cost roughly?

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12/19/2018 3:00 PM

Just get the ones from athena they fit the stock cylinder.

https://www.amazon.com/Athena-S410485303009-Power-Valve-Assembly/dp/B003CJ72S4

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12/19/2018 7:24 PM

I noticed the powervalve wasn't working correctly as the bike would bog on landings and it lacked bottom end torque. It wa a noticeable difference to say the least. The problem with pressing in a slightly oversized pin is that you will eventually end up with the same problem. The aluminum will stretch back out over time and the pins will fall out again. Been ther and done that. a 125 without a functional powervalve is a challenge to ride to say the least. Lol

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12/20/2018 10:06 AM

T981 wrote:

To solve this problem the easiest way you can also buy 2 ´spring type - straigth pins (iso 8752) in the correct size and place them in your povervalve.

Have done this before, second piston change on my '15 allready came with loose pins. Placed those pins an checked it every piston change after (5x at least) and never had issues again!

https://www.kramp.com/shop-nl/nl/1014164/2874589/188452/1481640+Spanstift+6x40
Link above is from a Dutch webshop, just use it as an example.

Hope you get your Yz running smooth again!

yz8103 wrote:

Thanks! How much do they cost roughly?

I don't think any more than 2 Dollars.
About the wearing out again part that is talked about below: since these pins are tensioned when pressed in, it will take a whole lot of wear before the pin comes out again!

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