Ok here is my guide to opening the powervalve on the servo assisted DTR's.The early models use the same method but there is no plastic pulley or cables to remove.
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
You may not like how the bike becomes in the bottom end of the rev range.It's down to your riding style i suppose but i can run a freshly rebuilt engine in with the valve open on the road no problems. Simply reverse the procedure to put it back to how it was.
There is no need to modify jetting or airbox snorkel.They are set up ready for a derestricted motor
