Yamaha ttr 90 dirt bike

"something with fuel". Clean fuel filter first. If no help, clean carburetor.

Test the stator those go in them quite a bit

If it is a 00 - 06 Yamaha TTR125/TTR125E it is 116 link.

If it is a 00 - 06 Yamaha TTR125L/TTR125LE it is 122 link.

I’m happy to help further over the phone at https://www.6ya.com/expert/al_e83b1941f9c0f302

A malfunctioning carburetor (running too rich) , will blow white smoke. I would start by checking the choke plunger, the seal could be leaking fuel. The plastic cap that holds the plunger on could be cracked and not holding the plunger in all the way. If you have re jetted the carburetor, perhaps the jet is too big. Your air filter could be plugged with dirt. All these things could cause a rich condition that would cause white smoke.

The pilot should be open. This is to say that if you look through it at a light you should be able to see through it.
I suggest blowing it out with compressed air as well as the hole it fits in. While your at it give all the jets a blow out.
once you've put it back together I also suggest you fit an in-line fuel filter.
This will help to keep the dirt out and save you having ths same problem again
Hope this helps
Regards Andrew Porrelli

Carba/f ratio needs adjusting and use of the choke will help keep the idle circuits clean.