DT125R ARCHIVE

you still have the servo fitted ?

1. Remove the front exhaust pipe
2. Look up the exhaust port (torch may help) and you will see the powervalve
at the top of the port
3. Turn the engine over by the kickstart to move the piston to the bottom of
the cylinder
4. Take off the cap on the left side of the barrel that the two cables go into
5. Disconnect both of the cables from the pulley.These cables will no longer
be used so you could move them out of the way under the tank or remove
the servo altogether.
6. Use the bolt in the middle of the pulley to turn the valve
7. While looking up the exhaust port rotate the valve until the valve is in the
open position.You will see when the valve is open as it enlarges the port
to its maximum size
8. Use your finger and feel up the exhaust port to make sure the valve is
sitting flush with the cylinder bore.Under no circumstances allow the valve
to protrude into the cylinder otherwise the piston WILL hit it.
9. Turn the motor over by the kickstart ( by hand) to make sure it rotates
freely.If it stops do not force it.The piston will be touching the valve
10. The valve must be locked in place so that it cannot move.The plastic
pulley has a small hole in it.I use a small drill bit that is a tight fit in this
hole.Behind the pulley should be a hole in the casting of the barrel.You
may need to remove the pulley and place it a different way to what it was
to get it all to align.Use the drill bit and push it through the pulley and
into the hole in the casting.Try to turn the valve using the bolt on the
pulley.The valve should not be able to move.
11. Recheck up the exhaust port to make sure the valve has not moved and
that it is still sitting flush
12. Refit the cap on the left side of the barrel
13. Refit the front exhaust
14. Diconnect the wiring to the servo or remove the servo altogether
15. Go pull some 2nd gear wheelies

All you need to know is here

http://www.dtr125.net/ypvsf.htm

But .........

Mine is a 1994 with 3 wire servo and as such the cables SHOULD crossover. When I connected it like this the valve turned the wrong way hence my cables are now not crossed over and the valve now turns the right way.

If the valve is working correctly you should get a good spread of torque/ power through the rev range right up to 10k ish