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yz8103
12/19/2018 11:00am
12/19/2018 11:00am
Edited Date/Time
12/19/2018 7:24pm
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...
The rod rotates and the springs pull on the little rods opening the power valves. Hate to say it but they are worn out.
The Shop
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
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+Spansti…
Link above is from a Dutch webshop, just use it as an example.
Hope you get your Yz running smooth again!
https://www.amazon.com/Athena-S410485303009-Power-Valve-Assembly/dp/B00…
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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