Time to change wheels and ...
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A slight rebore shouldn't affect the powervalve
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@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.
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@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 !
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@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.
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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 !
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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.
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@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.htmlThank you very much everyone, your answers are very useful.
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@yegor I'd recommend PJME, they're based in England but are Two Stroke Specialist, I believe they ship world wide.
Polishing will get you so far, gasket matching is going to be far more effective.
If you're going for performance, I'd avoid mitaka. Nothing wrong with them, but they are cheap CAST pistons designed to offer a cheap alternative to OEM.
For performance, go forged. Grab yourself a forged Wiesco piston and a set of chromium rings.
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@calum said in Time to change wheels and ...:
Grab yourself a forged Wiesco piston and a set of chromium rings.
can't find Wiseco ( one ring ?) piston for my model. But in PJME I have find Wossner piston ( 2 rings) , they are good I think, also forged (?)
Do you know if in PJME there Wiseco piston for the DT R ?
waiting answer from this site . http://www.paramimoto.com/pistones/343-wiseco-piston-yamaha-2-tiempos.html#/piston-dt_125_75_76_684m05600
