Question about expansion chamber

[trabantmk]

I have a 2002 dt125r and I want to derestrict it. I heard that there is something welded into the pipe and removing it can give you some power. Does anybody know something about this model of pipe? The code on the pipe is 3DD-14610

[Calum]

Have you tried the search:
https://dt125r.co.uk/topic/20/yamaha-dt125re-x-stock-exhaust-pipe

[Hark_Ptooie]

I also have a 2002, a "DE03". I bought an Athena pipe for 150€ which made it rev happily to 9500, then I fixed the reed switch in the speedometer which capped it to 80 km/h. Now it revs out to 120 km/h, should go faster if I swap the front sprocket.

The reed switch should not be removed, because the circuit is needed for some reason. Just pull it out of its socket behind the speedometer (you will find a square thing behind the 80 km/h position) , wrap it in tape, and tuck it in to the side in the housing.

The reed switch should not be confused with the reed valve, which is an entirely different thing.

I did not have to re-jet the carbs, they were fine default.

The Athena pipe did not fit very well, I had to use a bit of violence to get the screws in their sockets, but once there it had no issues.

[trabantmk]

Hey guys!
I cut it open and this was inside:
https://ibb.co/Jqpdjxs
https://ibb.co/YypvLLQ
https://ibb.co/BsGMGzP

[trabantmk]

@Hark_Ptooie Which Athena pipe did you put on?

[HOTSHOT III]

@Hark_Ptooie I found with the Tecno expansion chamber (basically identical to the Athena) it fitted a lot easier using the genuine Yamaha rubber grommet and spacer on the upper mount. The ID of the spacer is quite large and allows a little more movement to line it up than the grommet/spacer supplied..