Yamaha DT125lc DTR Pinned valve to servo conversion

[dandyman1]

As I have had a lack of or no response from anyone regarding parts and this conversion I would think either no one wants to help or no one knows anything about it! I have been doing some research and have come up with the following and hope it helps someone like me in the future! I wondered always why dtlc and dtrs had pinned valves?? I always thought it was because some parts had failed and owners did away with the servo etc.. then i thought it was to de-restrict the bike as lots of people said there bike was full power with the valve pinned open!!(not true)!! Well it seems that on uk bikes pinned valves was standard unless upgraded up until 1998 when it became standard to fit the servos. without the servo you are restricted to either no top end power or better bottom end power depending on where you pin your valve.. fully open gives you top end power but is not very rider friendly around town..and is low on power up to 7k rpm..ie not as many may think.. full power dts have a fully working power valve and have been de-restricted within the exhaust and via rev limiter.. any bike without a servo is not full power. may have full power at the top but thats only half the story!! so .. if you want to convert your pinned pv to a servo type its not that easy or cheap!! You will need a control unit assembly part 57U-85830-M0-00 these cost upto £300 these days.. if you can find one! Also a servo with cables that has the right electric connectors.. there are a few designs..cost £80 second hand. also you will need to expose the end of your pv and replace the end cap with a seal, spacer and bush followed by the pulley and pulley housing that accommodates the servo cables, parts 17-22 in the picture i will post up.. maybe more? or you may be able to use bolts etc from your set up.these parts will cost about £120 if your lucky and find them. Then I am also led to believe you may need to replace your cdi to one that the control unit fits too?? this i am uncertain on at the mo.. in fact please do add to this post if anything looks out of place or if you can enlighten us anymore! thanks.

[Sister Sledge]

I don't recall seeing an original post about this??

I always knew the valves were pinned to keep power down. I also knew that the pinned position would decide what power curve to give the engine.

Given you're looking at DTR parts lists and availability, I reckon you need to think wider for it. Surely a servo from a YPVS 350 would fit? The valves on twins are linked between the cylinders which means one servo does the job on both valves. The control unit will be similar too.
I reckon you need to also consider servos from motorcross bikes. They'll all more or less do the same job.
If you choose a second hand parts route then looking at other (similar) engines should provide what you need and far easier. It's definitely where I would be looking because new parts will likely cost more than a bike is worth.
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CCM 404 DS

[redeem ouzzer]

This is why it’s easier these days to buy a Euro spec DT or DTR with the YPVS gubbins already fitted then try and source the bits to retrofit the servo to a UK spec 12 bhp bike. The RD350 and TZR250 controllers and motors won’t work with the DT ignition system. Back in the day we used to lock the YPVS fully open and upjet slightly, made them fast but annoyingly peaky. Might be worth seeing if Borut at Zeeltronic does an integral CDI / YPVS controller for the DT, which would then mean you only need to find the servo unit and cables.
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Be a REAL MAN!

[stevo as b4]

As above, if your willing to spend the money then a Zeeltronic or Ignitec CDI box wired in to suit your bike is the best answer and this should allow any type of YPVS servo motor to work with the CDI.

The issue with some of the late European bikes, is that the YPVS valve does not fully open until after maximum power, and that the standard CDI is restricted by the ignition curve to never give the same performance as the early full power DTR's.

Additionally a programmable CDI will allow the best possible custom ignition map and powervalve open and closing strategy to be created to suit either the standard or any aftermarket exhaust.

Im not sure on which way the Zeeltronic CDI works, but you can have either an AC powered CDI from the stator windings, or you can do what I'm having done and wire in a DC powered CDI from a switched 12v power feed. There's advantages to both I've been told.

[yen_powell]

I'm sure I have heard of people connecting the oil pump cable to the power valve and then ran the bike on premix.
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Blackmail is a nasty word........but not as nasty as phlegm!
XT1200Z and a DR350 in bits

[Tankie]

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[dandyman1]

Sorry guys.. did not to mean to upset anyone here. I copied and pasted a topic and forgot to amend it before i posted it here!

I am looking for a dt specialists..electrics? or a wiring diagram of a dt with power valve servo operated.. with a 3 wire servo and a 5 wire servo lc mk3? if poss? or any?? cant get this info anywhere else. please help. not even HYANES!!!


thanks.

[dandyman1]

sorry please read below!!

[dandyman1]

I have now learnt that the dt125lc has the 5 wire servo.. they all go to the control unit.. the control unit plugs into the loom.. 1 brown 1 black connector.. which is live and earth and one rpm signal from the cdi which is black and white bullet connector or later models black and yellow.

on dtr from 88 they apparently did away with the control unit and incorporated it inside the servo which took it to only three wires.(servo that is). same as the old control unit.. 1 brown (pos) 1 black (earth) and 1 bullet from the cdi for rev signal.

In later models they went back to a 5 wire servo but it was controlled by a upgraded cdi with 12+ wires for restriction purpose..

my theory is I can run my 1987 dt125 lc mk3 on a early 90s dtr 3 wire servo in place of a control unit and 5 wire servo?? does this make sense? would this work? i think so...? any views? also any idea where i can get a wiring diagram for the European dtr from the early 90s? ie.. with a working power valve and 3 wire servo!!
many thanks