DT125R FORUM

@spookdog
No, I just decreased the spring preload a little to get 1/3 of the travel as sag. Didn't have to do much adjustment tho. No aftermarket dog bones or any other sht installed. So it is actually lower than stock. (it was 620mm between the two measurement points and now it is 600 if I recall correctly.)

Thank you guys for the replies
About that pie part, well im like eating too much but it just wont grab on me or idk

I will try basic setting in the front and removing mudguard.

Also one other thing, above 100 kmh if i just grab the clutch or push the handlebar the wobble starts. So I can like simulate the bad road or crosswind with this.

Previously it was 110 kmh top speed by speedo (115 by gps). Now it is 125 by speedo and 131 by gps. That is what my previous dt could do too, but that dt was indicating more on the speedo than actual. Strange but I can live with it

The acceleration howewer is much better. I'm only thinking I am too lightweight and the front forks expand that much that free play in the forks is too much? I will upload a photo later when I'm on computer. Bike has 26.000 kms on it.

Oh and I also tried going lower and higher tyre pressures than recommended. That also didn't change much. Stock is 1.8 bar in front and 2.0 bar rear as i recall. Tried 1.6/1.8 and going even for 2.2/2.4

Hello,

This is my second Yamaha DT125X, the previous one I sold was because it had slightly bent fork stanchions, I upgraded to a DRZ400 but I didn't like it's cruising speed so I bought another DTX which is really in good shape.

This DT had original exhaust on it so at first there wasn't any wobble as the accelereation was much slower and top speed also.

Now I have full giannelli, snorkel removed, upjetted, everything set up and as I shift to 6. gear I have the wobble again, so from 110 km/h and up.

What I did so far:
-Rebuilt front forks (this time not replacing bushings, on the previus DT I did but it was like even worse) with 10W oil, new fork and dust seal.
-Disassembled steering bearing and regreasing it, set it up so it is not loose and not binding.
Fork yokes are straight, fork stanchions are moving evenly free in yokes and wheel axle is free moving across the two fork legs.
-After installing front wheel, bouncing the bike a few times before tightening the two fork leg screws.
-Moving up forks like 1cm in the yokes.
-New Michelin Pilot Street Radial, static balanced it, and before installing the new tyre, I got the wheel balanced (by the spokes I mean, no runout at all)
-Tried increasing front spring preload by adding 9mm machined spacer on top of the stock 3mm one. (Between the spring and the top fork "screw")
-Setting rear sag (1/3 of the travel, I don't remember exact numbers now but it is set properly)

I am 160 CM and 55 KG if it means anything. I found the front forks too soft at first but now with the spacer I feel it is enough.

The wobble goes away as I step off the gas, and it is almost totally fine on good road surface and no wind. If I have cross wind and pretty big bumps, it is pretty scary.

I don't have any other ideas what could I try, perhaps I should install later a DRZ front complete or so?

Thanks in advance.

@oldman
Nice findings!

Could you also measure the other bushing for me? Just in case

So there should be no problem changing that if we find a fitting part

I found the sizes of the outer bushings for the wr125x: OD 45.00mm x ID 41.10mm x W 11.80mm x T 1.95mm
At worst, I will take the forks apart and replace only this if it matches even if there are no inner bushings available.

Also there is a hungarian website called oem-parts, on that site I can see the DTX outer/top bushing the same as the WR125X, 1-000-169-691

The inner/bottom bushes are 1-000-188-384 and it is DTX exclusive so I'm pretty shot at this point

Also you can't order any of them, they are unavailable.

For the DTRE, they are 1-000-165-981 and 1-000-137-166 respectively and they match with all the DTR's from the 90's. And they are available for order, lol, here you are:

https://oem-parts.hu/hu/parts/yamaha/motor/2005/dt125re-dt-125-1d03/front-fork

And I'm guessing that the DTRE and DTX forks are same if the DTRE is paioli too. The differences might be in spring, oil quantity, maybe the inner piston hole specifics and the lower fork legs because of the smaller brake disc/wheel shaft size. So the DTR/DTRE/DTX bottom bushing might be the same as well?

@Lorant2
Sorry, couldn't edit anymore.

Just found it in another post that they aren't available separately, just with the whole new lower forks. I haven't taken mine yet apart, but if you did, can you pull the bushing below the seal like usual? If so, could you even measure?

https://dt125r.co.uk/topic/673/dt125r-2000-fork-bushes

Hello,

I am also scheduling a fork rebuild on my DT125X, it does not leak at all and in unsprung state it doesn't have any play but if I hold the front brake and spring it in and out, there are centimetres of play and in high speed cornering I feel it unstable. Head bearing was recently replaced, new 32005 and 32006 Koyos instead of the crappy upper SAC 2547-1 which I was like unable to find but eventually I could, but just ended up installing tapered bearings to the upper slot too as it is same size.

I have some questions for like anybody who sees this. I know my forks are Paioli 41mm diameters. Are DTRE and even DTR-s 41mm too as I see it?

I found on yambits that "FBS007" is the upper bushing and is compatible with the RE and Yamaha WR125X which is like the same construction as my DTX so I guess that is same inner/outer/height diameters?

But as like you, I haven't found a lower bushing yet.
I haven't taken the bike apart yet, might wait for the winter season.

Thanks for your replies in advance.

@NINJA Thanks, I have to get the A1 licence now :face_with_tears_of_joy: But the summer will be definitely fun!

Managed to start it, has a nice engine and exhaust aaand airfilter sound

It is running smoothly so jetting is almost correct and needle position too, also starts if I just tap the starter button even without applying throttle. Only problem is it smoking if I apply full throttle, so I will have to adjust the air filter as it was cut open but a plate was glued back with 4 small holes, it has a mesh on the top of it for a little filter effect so I will just drill more holes later, also my plug is dark brown, needs more air.

I painted the resonator, and applied some exhaust gasket on the cylinder connection so it is not leaking, but it is missing the silencer rubber and the pipe that is part of the stock silencer was torn off at the welding so I will have my father to reweld it for me, then I paint that too.

Also applied some 10W universal indicators to rear because someone replaced them with 21W and the hazard switch wasn't working that way.

Engine sound
Startup like a boss

I believe they mostly do 4 stroke engines nowadays in a yamaha workshop, it was maybe too easy for them lol
I am doing my best to bring this bike back to life, and planning to keep it for a few years as I wont be having more money for a newer one in a while.
The piston is arriving tomorrow, I will make a video of the bike running if I manage to assemble it in the weekend. Main and Pilot jet arrived today

I just have contacted the local Yamaha official service by email. The bike was indeed serviced at them. But they only did the top end, I guess the bottom was made before that. They told me that a prox piston was installed, even though they only charged the previous owner like 70 euros for it which doesnt even cover the prox piston price, so I guess thwy just installed this 20 euro RAM piston. It is a mess that they just went over the fact that the power valve was definately hitting the piston.

Some update:

Imgur gallery

It is not on first oversize, but on the third one, 57.50. The cylinder looks like it was bored recently, it is still "matte", and the piston inside is "RAM" branded which you can get for 20 euro here. The problem is not the bad quality piston however.

They should have checked if the power valve has enough clearence to the piston. They definitely forgot this. As you can see, it is stucking at a point so much that I can't believe how it did not snap the second ring too.

Now, as the piston clearence is fairly big, but the engine was having a great sound, I will order a new piston that is the same quality as this (I have positive experiences with this brand in other bikes) and I will grind off a little off the PV, then assemble it with that, it still hasn't run in so I guess that I am safe to replace the cylinder. If it will be tight, I will take it to a cylinder bore specialist. And if it will start to rattle or become weak, I will take it off again and get the last size 58.00 bore with a Meteor piston.

Also, my starter motor arrived too! I just tried it, it spins the engine quite fast :grinning_face_with_smiling_eyes:
I might have the piston here by friday, and then I can work on it on the weekend. Also ordered a 25 PJ and 250 MJ for the bike (because it has gianelli and cut off top airbox) which will be here.

Okay, thank you, I will take off the cylinder and look into the top end. If it was really rebored 100km ago and the cylinder is not hurt, I will be trying to order a correct size piston ring for it and check if the power valve hits the piston and if the cylinder ports are "shaved down". I think I will be replacing the two seals too and then see what the bike does.

I was thinking about the same anyway, that the rotated power valve hit the ring, but then again it would have destroyed the bottom ring too. Also as I know, some older DTRs were restricted with a diamond shaped power valve which had to be rotated too.

imgur gallery
Before it was rotating but it was not changing, and on the other video it is rotated and aligned to the mark, I then further adjusted it to be in one with the cylinder.

@Jens-Eskildsen I did blow that too. I started it today too and went for a 10km ride. Couldnt get it past 70 kmh. Removed exhaust, and saw that the power valve does not opens despite it is turning on ignition. It was rotated by 180 degrees, I think they installed it incorrectly in the service. Also, found another major problem, one huge piece of the upper piston ring is teared down So i will have to disassemble the cylinder and replace the rings/get a new piston and rebore. I might be lucky that it tore off the front where only the exhaust port is and it got out. Also it was smoking quite hard while riding and it was working better with choke on. On low rpms it felt as it has air leak, on high rpm it didnt rev I think because of the power valve misfunction.

Am I right that only Athena and original head gasket is recommended to use?

And how hard is it to replace the right side crank seal? Does it need removing the whole clutch or just the little cog on the crank? For the left side I have to make a flywheel puller plate as I see.

Also, I currently have 220 MJ and 17,5 Pilot jet, am I right that I should start out with the standard DT125R setup 25 pilot jet and 240 main?

Some update:

I have removed everything again, reeds are perfect, intake manifold too. Boost bottle was a little loose so I replaced the clamp on it and it is better now, and managed to start the bike with a catch LOL

I put it in 6. , turn off ignition and bumped it a lot with choke on, then put it in 3. and managed to start it and rev it a little till I dropped the gas and it is not starting again. Also it was smoking a lot but it was revving freely and dropped the rpms nicely too like theres no air leak. I will try to further investigate it.

Also I had the air screw open at only 1/4 turns now. It was on 1 turns before and completely closed when I first disassembled it.

I mean that it works as it is intended. I turn the ignition key to on, power checks, and the kill switch is set to "run" I guess (I think it is pressed from the top to the bottom), anyway it is working as it is written on it. I believe this is not an electrical issue anymore, my plug is just not soaking in fuel and oil as it should despite the (I think) big compression. Tomorrow I will also have a friend to come over and we will check the exact PSI compression, what should be a correct value? Above 100, with full open throttle?

I cleaned all the earths a week ago when I was diagnosing the starter motor. The earth is clean on the battery, on the engine, on the HT coil and on the regulator too. If I set kill switch to off, then I dont have any spark, neither if I let my side stand down.

I checked the choke and it is not blocked, I blew it eith compressor. I will have a look at the reeds the following day. But I took a picture inside the intake manifold and it looks ok, I will have a look if it has increased gap then I will replace it, they are moving freely as I touched it gently with my hands. I will check if I can see through it, but then again that would cause flooding I think and my plug is not oily at all after bump starting it for meters.