DT125R FORUM

@Barron-1989 Yes white frame looking good Get yourself on here for a 3-wire servo but be warned, it'll go crazy at the end of the auction, I'd be bidding in the last 30 seconds if it was me: https://www.ebay.co.uk/itm/336567587789?_skw=Yamaha+DT125R+YPVS+Power+Valve+Servo+3+Wire+3MB-85820-00-00&itmmeta=01KQT8H9E0R37E9VYX7EPS2BN6&hash=item4e5cfdd3cd:g:bfgAAeSwr9dp-JC5 Other than that start looking around French and German breakers online as they're full of DTRs. The KTM LC2 125 trail bike (kind of an Austrian DTR) used the 3MB DT125RE engine and electrics and the 3-wire servo is the same so search for part numbers: 3MB-85820-00 (Yamaha) 51137095000 (KTM) https://www.trevorpopemotorcycles.co.uk/index.php?main_page=ktm_fiche_finder&model=112684&group=C96511304_080010&cat=3&bike_name=1998 125 LC2 100 (D)&section=1&groupname=CYLINDER HEAD EURO 125 96 I once purchased a number of BNIP LC2 servos which had both part numbers printed on the label and they were blatantly 3MB Yamaha 3-wire servos, sadly now all gone but if you're lucky you might find some somewhere. Re PV pulley and cables, the pulley and housing is identical to all other Yamaha '80s/'90s two-strokes apart from the RD500LC so any pulley and housing from an RD350YPVS, TZR/TDR/R1-Z250 or TZR125/TZR125R/TDR125 should fit (they're all stamped 29L which is the YPVS350 model code). I wouldn't recommend Yambits PV cables as the outers are very slightly the wrong length meaning you only get like 2-3mm thread engagement in the pulley housing with the PV adjusted correctly. Genuine cables are worth every penny or if you're into lubing cables after every wash like me, you can make your own here: https://dt125r.co.uk/post/28693

Shouldn't be too difficult. [image: s-l1600.jpg] You see the little dot on the balancer shaft cog, that should align with the corresponding dot on the crank gear. On the DTR, it's like the piston is at TDC for the dot to align. But should be simple enough.

Slow slow progress on this. Made a bit of a push on this the last couple of weeks. [image: chainFitted.jpg] New Renthal chain fitted. Bought some nice Apico foot rests and refitted/bled the front brake system. No surprises, but the original brake caliper was shot, completely seized solid.I managed to source another one, but one of the pistons was stuck. Once I addressed that, I found I was unable to pressurise the system, the master cylinder was shot. These bikes share the same master cylinder as the Cagiva Planet, but I was unable to source one of those for a reasonable price. I ended up getting a KTM Duke 390 front master cylinder as the closest match I could find. Front brake now bled and working. Bought lovely Hel lines front and back. The rear master cylinder's wiring loom was shot to buggery. The banjo switch was all snapped and the wires were merely soldered onto the bolt. A new genuine bolt, wire harness restored, then I designed and 3D printed the cover to secure it all into place. [image: banjoBoltCover.jpg] Need to reattach the rear brake master cylinder fluid reservoir and see what surprises are in store for me for the rear Hoping to continue to make progress on this as it's basically done. Just need to find original panels (or refurbish my ones for now).

@hotshot-iii hey, before assembly i adjusted the float height to 16-16.5mm according to the maintenance manual. I went through all ignition related cables and switches but nothing out of the ordinary. No corrosion etc... Also installed a genuine replacement coil and measured the primary and secondary winding just to be sure haha. The plug chop was done at 10k rpm. Did it a lot with mopeds to check if the main jetting was right. Today it was less hesitant to pull through so it went better when i just gave it full throttle from the go. This was after i finished the idle configuration with the screws. Steady +-1.6k rpm like the manual says and the air mixture screw is just about right. Temperature is very stable +-70 degrees celcius and its stay like that after driving almost an hour long. Im suspecting 2 things that are happening, correct me if im wrong haha. 1st thing is my powervalve that is opening a little bit to slow, i feel if they once open up, i can hear it and feel it and i can give them beans without any problem. Tohe other thing is maybe im running too rich in the lower rpms?

@reudtr88 The seller is right, the spacers and caliper bracket are narrower than the DT125R versions. The bench mock-up in the pics above comprised a 3ET DT200R swingarm, caliper hanger and spacers mated to a DT125R hub. As you can see the 428 sprockets lined up quite well (I also had to use a 3mm thick M20 washer between the caliper hanger and swingarm to get it as good as it could possibly be with the items I had to hand).

@Calum I hope you can find some time for that. It must indeed ride great with all those mods

That's so cool! It's been ages since I have been on my DT. I ought to sort the bits out on it and get it up and running again. My ETX is close to being done as well and that thing will rip when it's finished

Hi Calum, the OEM coil I ordered has arrived from Fowlers but the clear autolube pipe I ordered from e bay has not arrived. It is showing as running late when I check the tracking. I do not want to start the bike until the clear oil tube is fitted and bled so I am at the mercy of Royal Mail. Assuming the bike will run the only thing left to do is a couple of bulbs and then it should be ready for its MOT. I will fit a new plug cap similar to the one you show.

@Rallyfinnen ciao, grazie per il tuo post. Anch'io vorrei installare il 230 sulla mia TDR125R per avere più potenza. Rimango in attesa di tuoi cortesi aggiornamenti. Grazie

Hi John, Sounds like a lovely little time machine you've got there. Cracking bike and very very reliable, if it's not working, then it'll be something very simple and I am sure we'll be on hand to answer any questions you may have in an attempt to get you on the road again.

Thanks for that info Rallyfinnen

Definitely go the OEM route for sure.

@DTGREENLANER I'd say that's a dry bearing inside the servo somewhere, I think they can be taken apart and the gear train serviced. Never done one myself but it's pretty much a scaled-up RC car servo, just take your time and lay everything out in the order you removed it and you should be all good. Southeast Asia is full of DTRs, DT230 Lanzas etc. and some of those guys repair the servos quite often.

Yeah, I used a Honda CR85 Apico one on mine. I though the YZ 125 ones didn't fit.

@HOTSHOT-III thanks