Anyone know the stock jetting specs for this bike?

150 main 30 pilot, should be a 135 main at your elevation.

Is the needle set in the middle groove when shipped from the factory?

Yes it was, just saw other posts. Usually over 6500ft I run a 130 main. Used to change to 25 pilot, but lately have left it alone. I would change the spockets, 10t counter or up 1 tooth on the rear.

After opening the carb and inspecting the jets i found a 27.5 pilot and the needle in the second clip and a 145 main. I'm going to try a 30 pilot and needle in the third clip position and a 135 main. I'm hoping this change will add some more bottom end torque.

After opening the carb and inspecting the jets i found a 27.5 pilot and the needle in the second clip and a 145 main. I'm going to try a 30 pilot and needle in the third clip position and a 135 main. I'm hoping this change will add some more bottom end torque.

I think this jetting setup helped in developing more bottom end torque and a noticably quicker spoolup. I nstalled a v-force reed at the same time so im not sure which mod added how much boost but it does start easyer. I'm still getting a little pipe bang with the air screw set at 1 1/4 turns out. I think i'm going to install a 32.5 pilot and see if i cant get the air screw open a little further and get rid of the pipe bang.

Edited September 3, 201114 yr by Liviob

I installed the 32.5 pilot and this added a little more bottom torque. I can now get the air screw out to 1 1/2 turns out and i had to lower the idle a little. I will have to ride it in the mountains to see how this setup works in the sections.

I think i have settled on jetting that works good for my 7000' to 11,000' altitude. Main is 145, needle is #4 clip, pilot is 32.5. I may have to go to a #150 main. But for now this setup feels pretty good.

Edited September 21, 201114 yr by Liviob

After riding the bike again i decided that the carburator was still set a little lean. I did install a #150 main and i also decided to increase the pilot jet size to a #35. This change made a very noticable increase in bottom end torque and bottom end snap. The motor also pulls thru the middle and upper rpm range much stronger. I also had to reset the airscrew to two turns out from 1.5 turns out. These 250cc Beta motors are nice running motors. They are very easy to control.

Edited September 29, 201114 yr by Liviob

I know some altitude stuff from snowmobiles

Often you need to richen pilot for high altitude, it's not about the fact that there is less air etc it's simply that lower atmo pressure makes for less signal strength, that means the Venturi can't suck enough fuel through the pilot circuit, for the same reason a larger carb often needs bigger jets

Not uncommon to lean out main and needle and richen pilot, also if your needle adjustment stops making much difference you may have to go leaner on the emulsion tube

Compression it the other thing, high alt means lower compression, increase compression to raise combustion temperatures, you might be able to increase ign timing at high alt as well

Thanks for the info 0007. I am going to ride it this saturday. It's running pretty strong with the new carb setting. I think the ignition timing is set to stock specks. It's not as torquey feeling as my 290, but its not far off from it either.

The last carb settings that i mentioned work great in the sections. I am very amazed by the amount of smooth power the 250 makes. I did remove the clutch side flywheel and add a v-force3 reed to the engine and it did respond by producing a little more torque.