Yamaha DT 125 DERESTRICTING

[DTR+NSR]

@Lukas55 yours looks to have a earlier cdi which are considered the best.

[Lukas55]

@DTR-NSR Hmmm okay, that's great. It tops at 5500 rpms in 6 gear so it must be because of exhaust...

[SpookDog]

In my opinion, If it’s only doing 50mph, it’s not because of restrictions, it’s cause there is something wrong with it...
How long have you had the bike? Has it always been so slow? It might just be rebuilding time...

[Lukas55]

I have it for about 3 months and it was like that when I bought it. It had 13-57 gearing so I thought it's because of that but when I bought 16t front sprocket then I noticed it's something wrong... The piston and bearings in the crankshaft are changed 400km ago...

[Lukas55]

I removed the exhaust and the piston looks like this...
https://i.postimg.cc/Bj4tBnD6/adw.jpg
https://i.postimg.cc/xcrXqR1L/daw.jpg
https://i.postimg.cc/ykFkRZDt/daws.jpg

Btw is YVPS set good? Is it supposed to look like that in the cylinder?

[declan]

@Lukas55 looks like the ypvs can be set better did you have proof that the piston was changed

[Lukas55]

@declan
No ... Very stupid mistake, Next time I'll take off the exhaust to check ...Never can't trust people I guess.

[declan]

@Lukas55 the piston doesn't look too bad just doubt it was changed

[DTR+NSR]

Does it rev higher in the other gears? The powervalve looks ok.

[Lukas55]

Yes it revs little bit higher in lower gears.

[SpookDog]

I’m pretty sure that my power valve is set in the fully open position when the ignition is off. If you have a working power valve servo it’s set wrong...

[SpookDog]

All you’re gonna have to do is undo the pulley bolt and rotate the power valve till it’s ‘smooth’ with the exhaust port and refit the pulley. It should cycle closed then open when you turn on the ignition. It should only close again when you run the engine...
Should take you 30 mins, then enjoy!!

P.S. there’s a good chance that you will have to adjust the cables as well. Just make sure that the power valve is at the open/smooth position, that the pulley pointer/thing is set towards the little 3mm hole and adjust to fit..

[SpookDog]

By the way you have the power valve set I’m guessing you don’t really get past 7000 rpm in any gear?...

I have an early Dtr like yours. I also have a working power valve servo fitted. Finding out information on how to properly fit it was nearly impossible. I had to watch videos of 3wire servos starting up on ignition then running. I don’t know about later 5wire servos, but your power valve needs to be set in the ‘pinned open’ position when the engine isn’t running. The way it is set at the moment it is restricted and the servo will only try to close it more. It’s a wonder that it runs any sense at all the way it’s set...

[Calum]

@SpookDog That's how I usually set my valve.

I've never encountered problems aligning the valve.

Going from a completely broken setup to work.

Turn ignition on and off. This is how the powervalve should be when it is fully open.

So it is just a case of adjusting the cables so that the valve is flush with the exhaust port. In some instances people have put the cables around the wrong way so that it is not operating correctly. But that's easily rectified.

[SpookDog]

Yeah, the cables are clearly numbered 1 & 2. In my case they didn’t match up. I had to cut some outer off of one as well, to make it fit and work. unbelievable!

Getting the power valve fitted and the servo working was like one of the biggest mine-fields since the Somme ️

[Lukas55]

@SpookDog Thanks for advance dude!

[Lukas55]

Does my DT sound properly?
https://youtu.be/Id1jsvah8T8

[SpookDog]

I sounds like a dog!
Seriously though, it sounds a bit ‘clicky’ to my ear. A bit hesitant as well maybe...
It’s really hard to tell without being there and hearing the whole range of sound frequencies...

P.S. Have you done your power valve yet?...

[declan]

@Lukas55 hate to say it but that engine sounds screwed i trust that yeis hole is blocked on the inlet manifold right?

[Calum]

Yeah where is your YEIS bottle?