DT125R Carb tunning

[Ivanoel]

Hello,

I have a Yamaha DT125R of the year 2000 (http://www.bikepics.com/pictures/1562742/), it´s a stock motor, but with a firebox pipe and a SPES exhaust, with carbon power reeds.

It´s has a mikuni carb VM26SS (http://img87.imageshack.us/img87/2152/cimg1063tr8.jpg), the main jet is 210, Air jet 0.7, Jet needle 5J25, pilot jet 22.5, power jet 60. I don´t understand must about carb, and i want to have more power, a friend of my tells me to change the main jet to 240, and the other jet´s remains the same? this is not going to affect the misture? I will have more performance with the 240?

i appreciate some help.... Thanks

[Paulwhite]

Hello,

I have a Yamaha DT125R of the year 2000 (http://www.bikepics.com/pictures/1562742/), it´s a stock motor, but with a firebox pipe and a SPES exhaust, with carbon power reeds.

It´s has a mikuni carb VM26SS (http://img87.imageshack.us/img87/2152/cimg1063tr8.jpg), the main jet is 210, Air jet 0.7, Jet needle 5J25, pilot jet 22.5, power jet 60. I don´t understand must about carb, and i want to have more power, a friend of my tells me to change the main jet to 240, and the other jet´s remains the same? this is not going to affect the misture? I will have more performance with the 240?

i appreciate some help.... Thanks

you should get a bit more top end torque/speed with increasing the main jet size

but it shouldnt affect the running of the bike, you might have to change the needle position to get the mixture just right but do one thing at a time. just swap the jet and see how it feels then do a spark plug check and if its running too rich lower the needle by 1 notch ( pointy end facing the sky ) then see how it feels and do a spark plug check to see what the mixture is like.

but there are some other ways of getting more out of it but ul have to either wait for another reply or search the forums, i know there are loads of older topics to do with making the dt faster its just a case of looking for them.

[Ivanoel]

you should get a bit more top end torque/speed with increasing the main jet size

but it shouldnt affect the running of the bike, you might have to change the needle position to get the mixture just right but do one thing at a time. just swap the jet and see how it feels then do a spark plug check and if its running too rich lower the needle by 1 notch ( pointy end facing the sky ) then see how it feels and do a spark plug check to see what the mixture is like.

but there are some other ways of getting more out of it but ul have to either wait for another reply or search the forums, i know there are loads of older topics to do with making the dt faster its just a case of looking for them.

thanks

[Ivanoel]

you should get a bit more top end torque/speed with increasing the main jet size

but it shouldnt affect the running of the bike, you might have to change the needle position to get the mixture just right but do one thing at a time. just swap the jet and see how it feels then do a spark plug check and if its running too rich lower the needle by 1 notch ( pointy end facing the sky ) then see how it feels and do a spark plug check to see what the mixture is like.

but there are some other ways of getting more out of it but ul have to either wait for another reply or search the forums, i know there are loads of older topics to do with making the dt faster its just a case of looking for them.

Hello,

Firts sorry my english, i´m from portugal....

I was thinking, and, a tried an experience on the main jet, so i bougth a main jet with the same size 210, and i open the hole with a paper clip, a maybe the hole was to big. And when i drive the bike, the bike has instant power e them looses it and the engine chokes, going full throttle. when i gently acelerate everythinks find, but no fun at all.... So a put the original main jet (210) and it runs much better.

I goint to have the same problem with putting the main jet 240 or it´s going to be better?

i appreciate the help,

thanks

[Paulwhite]

Hello,

Firts sorry my english, i´m from portugal....

I was thinking, and, a tried an experience on the main jet, so i bougth a main jet with the same size 210, and i open the hole with a paper clip, a maybe the hole was to big. And when i drive the bike, the bike has instant power e them looses it and the engine chokes, going full throttle. when i gently acelerate everythinks find, but no fun at all.... So a put the original main jet (210) and it runs much better.

I goint to have the same problem with putting the main jet 240 or it´s going to be better?

i appreciate the help,

thanks

ok put the 240 main jet on

moove the carb needle down a notch ( pointy end facing up )

this should sort it out

[Airhead]

Opening up a jet with a paper clip was not a good idea. You should experiment with jets of different sizes. They are not expensive. I would suggest a 220 or a 230.

Abra um jacto com um clipe não era uma ideia boa. Deve experimentar com jactos de tamanhos diferentes. Não são caros. Sugeriria uns 220 ou uns 230.

...Paul

[Ivanoel]

thanks to all of you

[satelliteone]

not another 1, 210 is right on a stock motor, right compression! the 26 mikuni is a really great flat side carb.

Only way to increase power is increasing the compression. better port timming, and a better zorst.

The best guy to do any 2T work here in the UK is Stan stevens. google him..

TIP ..Have a look at the TZR RR spec..same engine as the DTR, u will notice some nice differnces! bigger carb!.. bigger compression. stage 3 barrel timmings!. And if u find a TZR RR model..give it to me..lol!...