Yamaha DT 125 DERESTRICTING
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You need to remove the pulley/cables from the end of the power valve, then rotate it anti-clockwise about a third of a turn (until you can see as much piston as possible) then replace the pulley/cables.
Check the the pulley moves clockwise, then back, when you turn the ignition key. If it moves anti-clockwise you have the cables back to front...
Please do this... -
@Lukas55 Lukas55 the piston shouldn't hit the valve what ever position it's in. The piston normally won't normally touch the valve unless your barrel has been re bored 57mm or more. And then you need to grind the valve down to create clearance.
In that pic you've just posted the plastic pulley is how it's supposed to be with the valve completely open. If you look up the exhuast port it should be more or less level all the way to the piston. If it is like that with the pulley in that position that parts set correct.
Then it's a case of making sure the valves in the correct position for what ever revs the engines doing. -
I was looking at the utube clip, not a pic. You can see the vertical seam where the 2 halves of the power valve fit together. It’s almost 2/3 to 3/4 closed!
Yes, move the power valve that way! (anti-clockwise) The pulley should fit snug back onto the diamond of the power valve after without adjusting the cables too much. You should be able to run your finger from the piston to the exhaust port outer edge without feeling any lips or hard edges. It should be smooth...
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@Lukas55 Took ages to find this post, thank God for the Search function.
https://www.youtube.com/watch?v=9eopT_gyAo4
I had the engine out my DT today, so under an inspection lamp I've taken the courtesy of creating a very short sweet video of the powervalve in its fully open, to fully closed back to fully open state.
Yours should match that operation.
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