Help on DT 125R powervalve

[dooinslark]

Can anyone give me advice on how to adjust the power valve on a DT 125 R, (2003 PLATE) I know where it is but not what to do with it. And is adjusting the power valve the same thing as " de-ristricting?) All comments welcome cheers

[stevo as b4]

Im not sure what you need to do on the 2003 DT, as becuase as you say the powervalve,servo motor and all cables are already fitted. I think from looking at a french DT125R site that you can adjust the cables so that the valve actually opens properly. It also looks like there is a plastic peg or similar behind the pulley on the side of the barrel, that stops the valve moving past a certain point. Id take off the cover and have a look to see exactly what is in there. If the cables and pully move depending on engine speed, then it is probably a case of adjusting the valve so that it opens fully when the servo motor operates. It easiest way to check for full opening of the valve, and what position the pulley is in at that point will be to take off the pipe so that you can see when the valve is fully raised in the port, and then mark the position on the pulley and or housing. You do know that there are at least 2 restrictors in the expansion chamber, one at the front pipe, and another in the first part of the tapered section, which can only be removed by cutting and re-welding the pipe. A replacement system is probably the better option. Also check the size of the main jet, as alot of restricted european DT's have around a 210 size main jet, and if you de-restrict the bike without fitting at main jet of between 260-280 size, it will likely seize.