DT125R FORUM

Cheers @HOTSHOT-III

Whoa.
Yes, it's a good thing we didn't ordered the wrong parts for my bike.

So you're saying i should check the carb?

If the cabling is not messed up the main light runs directly from the stator, doesn't load the battery.

@mbmO8 Nice to hear bud, enjoy 👍

@Hark_Ptooie I found with the Tecno expansion chamber (basically identical to the Athena) it fitted a lot easier using the genuine Yamaha rubber grommet and spacer on the upper mount. The ID of the spacer is quite large and allows a little more movement to line it up than the grommet/spacer supplied..

I am led to believe that the WR125X wheels are Saxxes wheels, not Excel like they were on the DTX.

That said, I thought they do fit, but you need the DTX setup etc, so the front brake, forks and spacers.

It's not a direct swap for the DTR setup, but it is a very simple swap.

if you buy a tail tidy online and fit it it will probably look good and work well but equally it can be very rewarding to sit down and design/make something that improves your bike and is unique.

@HOTSHOT-III That's where I spend most of my time these days. I can't remember the last time I rode my Yamaha, but I'm working on it most weekend 😛

6Nm rings a bell 🤣 Haynes is invaluable.

@dominik22 I'd start by refitting the airbox snorkel and the stock silencer if you have one. My French '93 4BL ran very well running the jet sizes you mentioned (i.e 240 main) with either a full stock exhaust system or a Tecno expansion/DEP silencer combo but it didn't like the stock expansion/aftermarket silencer combination.

Sometimes the tailpipe can affect performance as the stock expansion chamber and silencer are designed to work together; if you change one it can alter back pressure and mess with the pressure waves going backwards and forwards. These evacuate exhaust gases from the cylinder, assist in drawing fresh mixture up through the transfer ports and act to keep the fresh charge from escaping straight out the exhaust port. I never thought the tailpipe alone would affect this but once I tried a brand new DEP silencer on my otherwise stock French '93 4BL with 3NC CDI; it immediately refused to rev beyond 9k. I rode it around for about an hour to eliminate wind direction etc., came home and refitted the stock silencer and straight away it revved to 10k+ again. This is only personal experience, I don't have access to a dyno or anything but it made a big impression on me. A Tecno expansion chamber would probably work well with that Athena silencer.

Tecno expansion is identical to the Athena apart from the clearcoat and under half the price. Only downside is the clearcoat melts around the header pipe and is difficult to sand off making your bike look like a Crème Brûlée. If I bought another one now I'd paintstripper it and paint it heatproof black before fitting it. Very good quality pipe for the money, gives a more usable mid-range hit than the DEP which delivers peak HP revs about 600rpm later.

https://www.ebay.co.uk/itm/253780922884?gclid=Cj0KCQjwurS3BhCGARIsADdUH5215jUowscJtBepB7NQYPYfR4AeBV1Gu63S4cHFVVEN8aPRotYawA4aAoc7EALw_wcB&_ul=GB&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5339059258&toolid=10044&customid=Cj0KCQjwurS3BhCGARIsADdUH5215jUowscJtBepB7NQYPYfR4AeBV1Gu63S4cHFVVEN8aPRotYawA4aAoc7EALw_wcB

@Koltin As far as I know all pre-DTRE master cylinders are the same from 1988 until around 2004 so I'd start by comparing part numbers on Fowlers website, look up the part for say an '88, a '96 and your own bike:

https://www.fowlersparts.co.uk/?gad_source=1&gclid=CjwKCAjwl6-3BhBWEiwApN6_ks8FnxkMK8pUTlwAmDTt4wZ4GV5FlSqAj_zeubTOZF-qK69xd1CwVxoCpO4QAvD_BwE

Power on this run was 16.98 bhp.
On other runs it was 17.58. Without any mods.

Maybe it's from the 3ET DT200R,has the same carb as the DT125R but uses different numbering in jets, the main is 150 but is not smaller than the 210 of the DT125R.

I hoon around town on an unrestricted DTR and it uses less than 5 L/100 km.

Hello, I'm Paolo from Italy. I have a DT 125 red with grey frame. Do you know the RAL color of frame? Thanks!

No pics yet been busy though got a new motor for it managed to get it all in and running but got a strange problem ive put an orig air box on it and it wont idle I have to turn the air screw all the way in otherwise it takes a little time to down rev but then if I turn the screw to the 1 5/8s its supposed to be at or any where from seated its bogs out when you rev and has erratic idle takes ages to settle and cant decide what it wants to do even with 4 or 5 screws of the idle screw in out out it doesnt make much difference to idle speed.

So I am a bit stumped other than changing the coil pack and cdi as it went through plugs before and is now still doing something similar was fine on an 8 then it decided it didnt like that plug stalled and refused to start then did the same with another 8 I found a 7 and it starts and goes like stink when riding did 30mph up my steep hill testing it but its got that idle prob.

So i'm going to get some new plugs try and get funds for a coil and cdi maybe a new regulator as the voltage its a lil strange charges about 13.3 on idle to start off then after a few mins only sits at around 12.5 unless you rev crap out of it it will then go to 14.4

All fun and games any ideas welcome for me to test next time I get out to it would be appreciated. Trying to be careful and cycle it with the new piston so it beds in ok already got a strange rattle not sure if its just a bad bore settling in or a loose bit of old piston ring dancing around the crank but its whats going on with me and this lil ped for now thought ide send a quick update n ask a few questions from you seasoned vets.

Good that you've confirmed that it's not the powervalve, that's one thing we can rule out.

First things first, bin off that coil. Get yourself a genuine 3RM one.

https://www.fowlersparts.co.uk/parts/view/4RP8231026

I had a horrendous issue that took me months to diagnose, since it would run absolutely fine from cold-warm. But after a short while it just refused to rev. It took me literally forever to figure out, I swapped loads of bits out and considering my bike was a "fresh" rebuild I didn't think it would be the "Racing Coil" I bought. It hit me when my brother was having problems with his RD I noticed he had the same type of coil and the tuner said bin that immediately and all his problems went away!

So first things first, get yourself a genuine coil.

Later coils are a different part number:
https://www.fowlersparts.co.uk/parts/view/3KJ8231013

So it might be that your coil isn't right for your bike/year. So just source the correct year/model coil for your bike and make sure it's a genuine one (Denso I believe makes them).

Secondly, I've seen this before whereby the exhaust got full of water after a DTR was stood outside for a long period of time and this had very similar behaviour. Running rich and lacking the ability to rev/pull hard.

So whip that exhaust off and give it a good clean, it was very odd and not something I had considered.

Later model DTs were fitted 210 main jet, but again this all depends on your carb that you're running and whether or not you're fitting genuine Mikuni Jets. Ideally you want to be fitting the right jet for the year/ignition etc.

@Calum Sorry to hear about your car bud. +1 for I'd keep hold of those extra clutch cover inserts if I were you, they look ace and are a part that can get rubbed/scratched just from riding so it would be cool to be able to just bung on a fresh one as and when.

Frame looks same bottom end on tht looks like the dtr engine I have my 4hw has no cover over the oil pump and has some kind of make shift bracket for the oil cable. Looks like they chopped my frame and put a heavy duty swingarm on for that 4DL raised the coolant tank and put bat under the seat. Thats why I asked cause surely the 4 wires from the engine are the same or do I have to change the flywheel coil bit of forget its name now. I think i'll give it a bash as I got to remove the engine anyway if the mountings are the same and it wires up maybe I can put a DT rear sprocket on.

Food for thought ive got to get the energy to get at it first i'll look over that cdi wiring diagrams thing you shared and go from there just hope the exhaust mounts dont throw it out of whack.

I'm hands on so once got all the parts in sight i'll hopefully make sense of it all feel free to leave suggestions etc like I said before wish I had someone here to help me out going to be fun though so hopefully will give me more incentive.