Time to change wheels and ...

[Yegor]

Hello ! Now I will try to explain my situation with photos ( sorry for my english )))

first, I had a problem with yamaha dt lip seals ( water pump) ( the motorcycle was stopped more than half a year) , I changed it, but after that , the next day riding my bike the rear wheel suddenly blocked. Now I disarmed the cylinder and you can see whats going on. So I cant imagine why that happens , original cylinder and piston only 10000 km. And it's almost impossible to put it wrong the water pump and seal. ( or not

• The Yamaha DT 125R cylinder is sleeved ( iron ? ) can be repaired. or go for Athena )

• Can it be the fault of the oil pump ? how to check it¿ ( the engine thermostat works well.)

• ?

Usualy I buy in Wemoto.com . Thank you in advance !

[Calum]

Embed me!

Yeah, you can bore that out no problems.

Ensure you modify the powervalve to the right spec. Otherwise you will risk having the powervalve come into contact with the piston.

[Yegor]

@Calum You mean just adjust the power valve position ? ( cables ) Thx !

[Calum]

@yegor No, you physically have the modify the powervalve after a rebore.

[Irongamer727]

@yegor Athena!

[Irongamer727]

@yegor but sort out why it seized first please

[Yegor]

@Calum thx again! do you know how to extract the power valve from the cylinder ? ( for cleaning and modify )

@Irongamer727 Ok ! )) Do you need to readjust the oil lubrication after install the Athena kit ?

Thx a lot .

[Calum]

There is a bolt that goes through the powervalve, can be unscrewed from the front right of the cylinder. Behind the powervalve cover from the clutch cover side.

[Irongamer727]

@yegor some go premix some don't. I will go with the pump when installing my kit

[Jens Eskildsen]

A slight rebore shouldn't affect the powervalve

[Calum]

@jens-eskildsen Yes it will.

If the bore is stock (getting rarer these days and not worth assuming) then no, you're right. But once you start going over the first rebore size, modifying the valve is a must.

To save confusing, I said modify the valve just as a precaution.

[Yegor]

Yes, the cylinder was rebored at least once. Now I'm looking where do that again. Thx !!

@Calum > ?

[Calum]

@yegor Yeah that's the pup.

[Yegor]

@Calum **thanks to everyone ** . One question ( maybe a little bit stupid) XD . What material the cylinder is made of ? And the cylinder sleeve ? ( Yamaha DT 125R )

The cylinder sleeve Iron?
Cylinder Aluminium ?

Have you tuned Yamaha cylinder ? ( admision / exhaust transfers etc ?)

Cheers !

[Calum]

@yegor YEah that's correct. I imagine the bore will be a steel alloy.

I've had my barrel ported by a tuner.

[declan]

@calum how much did that cost bud and can it just bolt back on no jet changes etc

[Calum]

@declan No, porting is going to drastically change the characteristics of a two stroke engine.

I wouldn't advise it on a daily, or on stock ignition.

You don't get something for nothing. I'm not going into it here, but the principle is, peak almost always alters performance elsewhere, usually torque.

There are exceptions where engines are poorly designed and modifications improve performance with no effect. But the end of it is, these engines are pretty well designed. When it comes to porting them, you're making a sacrafice somewhere else in the rev range for more power.

[Yegor]

Hello ) !
I will go tomorrow to the workshop with the cylinder for bore. I know is privileged information and long testing time but do you know where I can find information about tuning cylinder transfers, I think is good idea do something there before it will be bored. Maybe in the same workshop they do that for extra €, will ask.

all this marked with color dots can be modified/enlarged : ?

at the top of ALL the transfers: (?)

so, thank you again for the help, and gas gas !

[Calum]

Depending on how good your English reading is, I HIGHLY recommend Graham Bell's Two Stroke Performance Tuning.

That will give you a lot of knowledge on tuning two strokes.

I would NOT recommend porting the barrel, or altering the port timings, without a programmable CDI.

[Yegor]

@calum said in Time to change wheels and ...:

Graham Bell's Two Stroke Performance Tuning

Thanks for the tip Calum . also I have dowloaded the Two-Stroke TUNER'S HANDBOOK By Gordon Jennings. Time to read.
( http://www.2strokeengine.net/gordonjennings/twostroketunershandbook.php )

so, for now I'm going to polish a little bit where it is needed , also the power valve , because it is very dirty.
Mitaka pistons are good ? where you can buy original Yamaha DT R parts online ( like water pump complete repair kit) ? <--- have find this official site : http://www.recambios-yamaha.com/es/dt125r/2002/bomba-de-agua.html

Thank you very much everyone, your answers are very useful.