Untitled

De-restricting a DT125R
'88-'96 models
For '97-'99 models click here
For '00-'03 models click here
For '04-onwards models click here

Early DTR's are easier to de-restrict than later ones. The early ones are restricted mainly in two areas:

The exhaust on '89 to '98 models have a small piece of pipe welded into the flange end, which can be removed by using a DREMEL to cut the three welding seems.

This is the restrictor piece removed.

The UK version ('89-'96) comes with the Power Valve (YPVS) pegged shut and no servo to operate it. By fully opening the Power Valve you will lose power at low revs, but as the revs get to around 6500rpm you will hit the power-band and it'll fly!
Ideally, it would be better to fit a Servo Kit but i've heard that these are hard to find second-hand, as there are a lot of people trying to get hold of them. If you are lucky enough to find one, then look at the fitting instructions sheet that i've put in the "YPVS info" section.
On the other hand you could buy the servo, pulley and all the other parts NEW from your local Yamaha dealer. I know that the pulley housings, pulley and all the screws come to Ł30 when i bought them for mine. I think the Servo is priced somewhere in the region of Ł150
P.S. When asking for the servo kit parts, ask for the parts for a 1997 model (because I know that that model had them fitted).
Anyway, to open the power valve, remove the left-hand valve cover on the cylinder barrel, followed by the brass sleeve. Remove the front exhaust pipe. Now turn the end of the power valve round until, when you look up the exhaust port you can see the grooved part line up with the top of the exhaust port. If not, feel up the port with your finger and fine adjust it.

Because the purpose of the left-hand side end-cap is to hold the power valve in the same position and seeing as you've moved it, you might need to knock the small pin out of the end-cap which engages into the brass sleeve, this will mean that you can slide the brass sleeve on to the end of the power valve then fit the end-cap without it trying to move the valve round.
Or, you could cut a new slot in the brass bush to ensure that the valve doesn't move once the end cap is put back on.

Look up the exhaust port after refitting the end-cap to check that the power valve hasn't moved. Put the exhaust back on and you're finished.

	The exhaust on '89 to '98 models have a small piece of pipe welded into the flange end, which can be removed by using a DREMEL to cut the three welding seems.
This is the restrictor piece removed.
The UK version ('89-'96) comes with the Power Valve (YPVS) pegged shut and no servo to operate it. By fully opening the Power Valve you will lose power at low revs, but as the revs get to around 6500rpm you will hit the power-band and it'll fly! Ideally, it would be better to fit a Servo Kit but i've heard that these are hard to find second-hand, as there are a lot of people trying to get hold of them. If you are lucky enough to find one, then look at the fitting instructions sheet that i've put in the "YPVS info" section. On the other hand you could buy the servo, pulley and all the other parts NEW from your local Yamaha dealer. I know that the pulley housings, pulley and all the screws come to Ł30 when i bought them for mine. I think the Servo is priced somewhere in the region of Ł150 P.S. When asking for the servo kit parts, ask for the parts for a 1997 model (because I know that that model had them fitted). Anyway, to open the power valve, remove the left-hand valve cover on the cylinder barrel, followed by the brass sleeve. Remove the front exhaust pipe. Now turn the end of the power valve round until, when you look up the exhaust port you can see the grooved part line up with the top of the exhaust port. If not, feel up the port with your finger and fine adjust it.
	Because the purpose of the left-hand side end-cap is to hold the power valve in the same position and seeing as you've moved it, you might need to knock the small pin out of the end-cap which engages into the brass sleeve, this will mean that you can slide the brass sleeve on to the end of the power valve then fit the end-cap without it trying to move the valve round. Or, you could cut a new slot in the brass bush to ensure that the valve doesn't move once the end cap is put back on.
Look up the exhaust port after refitting the end-cap to check that the power valve hasn't moved. Put the exhaust back on and you're finished.