De Restricting my DT125R

[Airhead]

This thread is a chronicle of the things I did to de-restrict my fully restricted DT125R, If you are on 'L' plates this is something you can do after you pass your full bike test and not before.

Well stage one has been sorted, I took off the exhaust and found one of those tube within a tube things in there so out came the dremel again, heres some before and afters, the last pic shows just how severe this thing is compared to the one i found in my DT175MX

Comparison with the restriction i removed from my DT175MX

[2 Wheels]

Am i seeing this right ?

So you have the exaust, then inside that there is a straight piece of pipe, then inside that there is that beveled piece of pipe. If so -- major restrict straight away!

[Cynic]

Well stage one has been sorted,

I've been looking into this OG and so far as i have found the main restriction apart from the exhaust is the PV servo pulleys and cable arrangement. In restricted form you don't get fully open, japaneese market parts (ie unrestricted)is the way to go apparently. I haven't been able to confirm this yet so it may be just internet rumour.

To go with the PV change there is a minor re jetting needed to cope with full chat. Again not confirmed but back in the day we used to stick 240 mains in TZR's when we flipped the valves or they cooked and siezed at full chat.

I'll keep digging.

[Airhead]

Am i seeing this right ?

So you have the exaust, then inside that there is a straight piece of pipe, then inside that there is that beveled piece of pipe. If so -- major restrict straight away!

Just the bevelled one in the 125, the other straight one came from my 175. I doubt your 125 has this restriction because no one would put up with that for more than two weeks

[Airhead]

I've been looking into this OG and so far as i have found the main restriction apart from the exhaust is the PV servo pulleys and cable arrangement. In restricted form you don't get fully open, japaneese market parts (ie unrestricted)is the way to go apparently. I haven't been able to confirm this yet so it may be just internet rumour.

To go with the PV change there is a minor re jetting needed to cope with full chat. Again not confirmed but back in the day we used to stick 240 mains in TZR's when we flipped the valves or they cooked and siezed at full chat.

I'll keep digging.

I've not heard of this pulley thing but have heard of a 180 'flip' of the PV. not sure how to identify if this is needed with mine though. Let me now what you find out

Other things to check are the 'snorkel' from the airbox under the seat.

The speed limiter in the speedo (reed switch i think)

Gutting or replacing the exhaust pipe

The silencer

[Cynic]

I've not heard of this pulley thing but have heard of a 180 'flip' of the PV. not sure how to identify if this is needed with mine though. Let me now what you find out

Other things to check are the 'snorkel' from the airbox under the seat.

The speed limiter in the speedo (reed switch i think)

Gutting or replacing the exhaust pipe

The silencer

I suppose while the exhaust is off now would be a good time to check out the valve opperation. It should do a full cycle as a cleaning/center opperation when you switch the ig on. With the exhaust off you can see if it follows a full arc. Strategic use of the ig switch and you should be able to check the valve travels fully open and back to 'closed'.

Other than that this is worth a read. http://www.dtr125.net/tuningnewer.htm

I still think there is more in them. I can't see those mods giving the 10-12HP that the bikes loose in restricted form.

[Guest MaD.VeZ]

The CDI is a big restricting factor on the newer models, since the cdi controls ignition and YPVS it makes sense. Iirc you need one from a pre 98 model for the full power.

There is some info on a German forum about rewiring them to overcome the restriction >Translated page <wont link to the exact page, just click werkstatt on the top bar, then click through the links in the upper right corner in the grey box. If anyone is electrically savvy i would like to know if its a viable mod.

Vez.

[Cynic]

Sort of, i've been looking into this the tricky bit is for that to work you need the entire ig/powervalve electrics and all the black boxes to suit for the pre98 stuff to work.

And as far as it goes its a pretty good angle as the pre 98 bikes didnt have any powervalve electrics. That was the primary restriction. So fit the kit and hey whoopsie around 22-24hp. Obviously you need jetting,pipe,filter etc too.

The 2003 unfortunately has the PV fitted and working as it should to smooth the power out. Trouble is the carb/exhaust combo with some PV tweaks is what has brought the bike down to 12hp. But unlike the older stuff you can't just stroll into your yam dealer with 3-400 quid and take away all the parts you need for full power.

I have heard stories of cutting one of the cdi wires but i think that is just a variation on the reed switch in the spedometer. Just flipping the valve isn't any good either as that makes it a pig to ride.

I would say OG just wants some more poke rather than a ragged race thing and as such as a collective i don't see why we cant sort out some proper correct stuff to add to Ryan09's sticky.

[Airhead]

Been out today, the exhaust is back on so i didnt see the PV working. It does the cleaning cycle ok when i switch the ig on. today it performed a lot better but theres still loads left. My exhaust is still number 1 suspect and the next thing to do is 'gut it' and get a new tail pipe, Cynic you are quite right, just want a revvy bike not a sluggish one like it is now, still it was good to be out today

just got quoted £250 ish for a mph speedo which i am not prepared to pay, ordered a veypor digital one at around £150

[Cynic]

Been out today, the exhaust is back on so i didnt see the PV working. It does the cleaning cycle ok when i switch the ig on. today it performed a lot better but theres still loads left. My exhaust is still number 1 suspect and the next thing to do is 'gut it' and get a new tail pipe, Cynic you are quite right, just want a revvy bike not a sluggish one like it is now, still it was good to be out today

just got quoted £250 ish for a mph speedo which i am not prepared to pay, ordered a veypor digital one at around £150

So knocking out the connection to the reed switch and a pipe should have you flying. There is another restriction in the pipe oon the 'UP' section of the expantion chamber and crucially the stinger at the back of the exp chamber will be tuned to work best with 12hp so a good pipe will probably in all be a better option.

Are we keeping all the cast offs for any possible return to std. And i totally agree on the clocks, the KPH clock on my TDR lasted less than a tank of gas before i swapped it over. Surely there must be 2nd hand ones about for your DT?

[Guest MaD.VeZ]

I probably have a set of clocks, not sure on the condition though.you want me to dig them out?. Also have two expansion chambers doing nothing but gathering dust.

I'm sure the pre 98 bikes did have the PV electrics as both my 97 and the 88 have an empty connector block on the cdi (thats not in the manual presumably for the PV). The 88 may have been changed, but the 97 hasn't, only been 2 owners before me and i knew them both, I'm sure they would have mentioned changing it. Although i am aware since the 99 model there have been alot of different electrical changes, i believe mainly trying to restrict the bike in one way or another, one of these changes involved fitting an extra box to control the PV or at least retard it iirc.

From what i have read on the German forum and a few others, even with the power valve servo fitted, the valve is sometimes 180 out. Just talked to a German with good English who said he would take a look at the site when he gets time and give me a better translation, which may reveal a little more info.

As for the reed switch i don't think it needs disconnecting as much as just moving away from the speedo face, but fitting an after-market speedo may solve this. I haven't heard why, but there are warnings against cutting the reed switch out all together, maybe this is because of the connection to the CDI cynic mentioned? I think some investigation/research is required before removal of the original clocks IMHO.

[Cynic]

  I probably have a set of clocks, not sure on the condition though.you want me to dig them out?. Also have two expansion chambers doing nothing but gathering dust.

I'm sure the pre 98 bikes did have the PV electrics as both my 97 and the 88 have an empty connector block on the cdi (thats not in the manual presumably for the PV). The 88 may have been changed, but the 97 hasn't, only been 2 owners before me and i knew them both, I'm sure they would have mentioned changing it. Although i am aware since the 99 model there have been alot of different electrical changes, i believe mainly trying to restrict the bike in one way or another, one of these changes involved fitting an extra box to control the PV or at least retard it iirc.

From what i have read on the German forum and a few others, even with the power valve servo fitted, the valve is sometimes 180 out. Just talked to a German with good English who said he would take a look at the site when he gets time and give me a better translation, which may reveal a little more info.

As for the reed switch i don't think it needs disconnecting as much as just moving away from the speedo face, but fitting an after-market speedo may solve this. I haven't heard why, but there are warnings against cutting the reed switch out all together, maybe this is because of the connection to the CDI cynic mentioned?  I think some investigation/research is required before removal of the original clocks IMHO. 

Sorry bad discription, they had the provision in the loom for the PV but no PV controller (thats what plugs into the CDI) or the servo and pulley system.

But they have changed the cdi after 99 as that model has the PV and to retro fit the old cdi, you will also need the old controller and i believe the servo etc from the pre98 bikes.

I seem to recall JimR was good with PV stuff. Is he still on?

[Cynic]

Have a look at this elec drwg from Dewpy's clicky.

Item 9 being the cdi its shows the connection to the reed sw everybody gets so excited about. Its shown in its idle state, or should be according to electrical drawing convention. Therefore when the bike hits whatever speed the switch is sensitive to, it will make the connection and apparently retard the PV. I cannot see the benefits of earthing it though. You would have to know the intermal workings to determine that for certain. More importantly if you get it arse about face and earth the wrong connection you could cap you pv in all gears.

Sorry its a bit big.

[Guest MaD.VeZ]

Its hard to tell from the schematic, but it doesn't look like the wire from the reed switch to the PV is an earth(its black for earth, it is on the all of mine). As far as im aware the reed switch works with magnets detecting when the speedo needle is at a certain point, and then activates the reed switch thus retarding the PV. It looks like you may have to either join or disconnect the 2 wires entering the reed switch to prevent the PV retarding, which, i don't know. There is the chance that the reed switch contains some kind of resistor that changes the current before returning to the PV, which could cause issues/damage to the cdi if the reed switch is removed completely and the wires joined. Think the reed switch would need to be checked over with a multi meter before attempting to join the wires.

Alot of guess work on my part though, think we need someone in the know to answer this one.

[Cynic]

 Its hard to tell from the schematic, but it doesn't look like the wire from the reed switch to the PV is an earth(its black for earth, it is on the all of mine). As far as im aware the reed switch works with magnets detecting when the speedo needle is at a certain point, and then activates the reed switch thus retarding the PV. It looks like you may have to either join or disconnect the 2 wires entering the reed switch to prevent the PV retarding, which, i don't know. There is the chance that the reed switch contains some kind of resistor that changes the current before returning to the PV, which could cause issues/damage to the cdi if the reed switch is removed completely and the wires joined. Think the reed switch would need to be checked over with a multi meter before attempting to join the wires.

Alot of guess work on my part though, think we need someone in the know to answer this one.

Hmm i wonder if it pulses, the most common fix i've found that can be reasonably trusted (a couple of the German sites agree to although the translations aren't great)says remove it from the spedo housing but don't cut anything. Just get it out the way in the headlight fairing somewhere.

[Guest MaD.VeZ]

Hmm i wonder if it pulses, the most common fix i've found that can be reasonably trusted (a couple of the German sites agree to although the translations aren't great)says remove it from the spedo housing but don't cut anything. Just get it out the way in the headlight fairing somewhere.

Yeah thats my thoughts also. keep it but move it. 

[Airhead]

Thats what i will be doing, remove and tuck away. I know someone from another forum, he has done this as well as gut the exhaust and jet up and his bike goes well from all accounts.

What have you done to yours Vez or was it all done before you got it ?

[Guest MaD.VeZ]

Thats what i will be doing, remove and tuck away. I know someone from another forum, he has done this as well as gut the exhaust and jet up and his bike goes well from all accounts.

What have you done to yours Vez or was it all done before you got it ?

I have put a Big-one exhaust and Renthal bars on the DTRE(had from new) and earthed the black/green wire, not jetted up yet but probably should. 55mph calculated. head down ass up, with the wind behind me downhill slipstreaming a group of bigger bikes.

The 97 DTR has had all sorts done to it, was standard when i got it. Had the barrel ported and skimmed, polished piston, exhaust gutted, carbon reeds, pipercross air filter, bigger jet(240 iirc), PV rotated and pinned to fully open, 1 tooth added to front sproket(17 iirc), removed the 2-stroke pump, fitted a single throttle cable and braided hoses, also added a pair of DID alloy rims(which were trashed soon after in an argument with a tree). Thats most of what i can remember. Wouldn't want to take it on the road as you have to ride the power-band all the time, but its great fun on the dirt and goes like stink. Passed a guy on a KMX125 once, he asked me if it was a 250. Seen 90mph on the clock on dirt, probably about 80mph actual though.

Had alot of help with it from a very knowledgeable friend, who's sadly passed away since.

[2 Wheels]

I to am derestricting my dt and have been looking into this.

You all prob know this -- but anyway--

We want the PV to work as it should because without it there is no power at low/medium revs.

The PV is fuly closed when it is 1/3 of the exaust port and fully open it is the with of the exaust port. This is what it does in its check when the IG is turned on. Even in its retarded state this is it working proper.

The CDI is the heart/brains of the bike, the reed switch (along with everything else) is conected to it.

With the bike on full throtle the PV is fully open until "whatever revs/mph" the CDI tells the reed switch to retard the PV via the servo pully.

Takeing the reed switch outa the speedo will mean the CDI doesnt know what revs/mph the bike is doing so it cant tell the reed switch to retard the PV.

This is what we want as the PV will not retard when the bike is on full throtle and will still work proper at low revs.

I think this is all we can do to the PV and the other thinks are the exaust pipe and a 240 main jet. The bike is currently on a 210 main jet.

I (like Cynic) dont think this is enough of a restriction to take the bike down by 10hp.

What I am wondering is -- is the CDI itself permanatly retarded by yamaha for this bike --- they wont tell us jack shit !

Im not that good on the electricks side of bikes and was wondering is there a way arround the CDI, I know we need the CDI for the IG timing and things but i wonder is there some way arround it.

ps. I am not trying to make a race bike outa my dt, all i want is (like OldGit) a few more horses.

What ya think ?

EDIT: The 180 filp talked about is only if the PV was taken outa the barel for cleaning or something. It is then possible to put the PV back in 180 the wrong way arround, this would mean the exaust port would never open fully and would be 1/3 closed off all the time.

[Guest MaD.VeZ]

I to am derestricting my dt and have been looking into this.

You all prob know this -- but anyway--

We want the PV to work as it should because without it there is no power at low/medium revs.

The PV is fuly closed when it is 1/3 of the exaust port and fully open it is the with of the exaust port. This is what it does in its check when the IG is turned on. Even in its retarded state this is it working proper.

The CDI is the heart/brains of the bike, the reed switch (along with everything else) is conected to it.

With the bike on full throtle the PV is fully open until "whatever revs/mph" the CDI tells the reed switch to retard the PV via the servo pully.

Takeing the reed switch outa the speedo will mean the CDI doesnt know what revs/mph the bike is doing so it cant tell the reed switch to retard the PV.

This is what we want as the PV will not retard when the bike is on full throtle and will still work proper at low revs.

I think this is all we can do to the PV and the other thinks are the exaust pipe and a 240 main jet. The bike is currently on a 210 main jet.

I (like Cynic) dont think this is enough of a restriction to take the bike down by 10hp.

What I am wondering is -- is the CDI itself permanatly retarded by yamaha for this bike --- they wont tell us jack shit !

Im not that good on the electricks side of bikes and was wondering is there a way arround the CDI, I know we need the CDI for the IG timing and things but i wonder is there some way arround it.

ps. I am not trying to make a race bike outa my dt, all i want is (like OldGit) a few more horses.

What ya think ?

EDIT: The 180 filp talked about is only if the PV was taken outa the barel for cleaning or something. It is then possible to put the PV back in 180 the wrong way arround, this would mean the exaust port would never open fully and would be 1/3 closed off all the time.

Yes the cdi is restricted on post 98 bikes. Yes there is a way around this, but its in German.(the link is further up this thread)

Vez