DT125R FORUM

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.

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.

@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?

@NINJA I cleaned it completely, even removed the atomiser tube to make sure the holes arent blocked. Gaskets are fine it is not leaking and fuel level is correct. Has 17.5 air jet and 220 main jet which might be small considering that it has gianelli but it shouldn't be a problem to start it, especially since it has run with this setup for the previous owner. Power valve servo works as it checks, and it is set to the mark on the cylinder.