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Yamaha DT125R Powervalve Problems... Please advise....

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s3pro
L Plate Warrior



Joined: 31 Jul 2008
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PostPosted: 10:56 - 31 Jul 2008    Post subject: Yamaha DT125R Powervalve Problems... Please advise.... Reply with quote

Hi all on here.. I'm wondering if anyone can help me with this problem.. I have a 1996 Yamaha DT125R. When I first bought the bike it came with the powervalve pegged shut. I bought all of the kit to enable the powervalve as needed. Connected the motor and had a friend set it all up. The problem that I have is that the valve doesnt seem to open fully at high revs and wont go past 6500rpm. The only restriction I can possibly think of that I havnt covered is the CDI unit. I looked at that and found it was coverered in grime. As I wiped it off I realised the number on the side of the cdi unit came off with the grime, so I dont know if this is a replacement CDI or original. I even bought some new servo cables but it still wont open fully. I have been to this site http://www.dtr125.net still have the same problem. Can anyone possibly point me in the right direction? Any help would be great.. Thanx
Richard
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mad cookie
Derestricted Danger



Joined: 11 Mar 2009
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PostPosted: 01:58 - 24 Mar 2009    Post subject: dt125r Reply with quote

hello mate ive just read your post i own a 1996 dtr myself and was wondering if u have the cables off the servo the wrong way round on mine the cables go straight and not crossed if you no what i mean and allso have you got a race front pipe or standerd ???
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mad cookie
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Joined: 11 Mar 2009
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PostPosted: 01:59 - 24 Mar 2009    Post subject: dt125r Reply with quote

hello mate ive just read your post i own a 1996 dtr myself and was wondering if u have the cables off the servo the wrong way round on mine the cables go straight and not crossed if you no what i mean and allso have you got a race front pipe or standerd ???
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Billing
World Chat Champion



Joined: 12 Mar 2009
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PostPosted: 09:17 - 24 Mar 2009    Post subject: Reply with quote

take the exhauste off, get a small torch. turn the ignition on but don't star the bike. the pv servo should make a buzzing or whirring noise. Then IF I remember rightly when you twist the throttle at the handle bar the pv should move, turn the throttle to the end stop then shine your torch up the exhaust port and have a look if its fully opened Thumbs Up
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ben350
Trackday Trickster



Joined: 29 Apr 2008
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PostPosted: 12:13 - 24 Mar 2009    Post subject: Reply with quote

Partially true, but the power valve bobbin will turn by itself not by turning the throttle.

Make sure your battery is in good condition / fully charged as sometimes this causes power valve problems.

With the little PV cover off on the left side of the engine you will be able to see if its all set up correctly as the PV pulley (where x2 cables attach) has a wee tab comming off it which should line up with an approx 5mm hole in the cylinder side behind it Wink
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eazy rider
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Joined: 26 May 2009
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PostPosted: 21:50 - 04 Jun 2009    Post subject: Reply with quote

There is another restrictor in the downpipe which you'll need to remove for full performance.

Did you take the plastic bit out and turn it 180 degrees then slot it back in before you attached the cables?
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prawny1
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Joined: 28 Jun 2005
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PostPosted: 22:03 - 04 Jun 2009    Post subject: Reply with quote

What year bike did the power valve servo come from?

The later models that come with a pv servo as standard, also have a electrical restriction, so the servo starts to open then changes direction at 6500 rpm closing the valve again, i don't know if that restriction is integrated into the servo or the rest of the loom/cdi, but if it is part of the servo circuit then the loom for your bike wont operate the servo properly.

I used a pv servo and valve gear from a late tzr 125 rr that i got for free of a crashed import (imports have the servo attached as standard) with late dtr cables because the dtr pv kits are hard to come by.
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stirlinggaz
World Chat Champion



Joined: 22 Jul 2007
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PostPosted: 22:08 - 04 Jun 2009    Post subject: Reply with quote

hi,
only ever set up the ypvs on a dt once.
& i followed the instructions here : http://www.dtr125.net/tuningf.htm
including the bit on the standard exhaust (not applicable if you have a dep or big one FULL exhaust system)
easy to follow pics & it worked for me!
also has instructions on the electrical restriction on the later models (the grey box)
cheers,
GAZ
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