2001 yz144 jetting....

[yz125rider21]

wondering anyone had done this on there yz144 2001 to save me a lot of time trying to figure it out :-)...got it back fomr Eric and had a piece brake in the mail and had a slight delay but now I have it all together waiting to jet it....any ideas???

 

[lwsmithjr]

I have an '05 YZ144 from Mr. Gorr.

Jetting is as follows:
420 Main
40 Pilot
Needle Clip 3rd position

Now, We are also at sea level, bike has a V-Force 3, PC pipe and shorty silencer. All of this will have an effect on jetting.

 

[yz125rider21]

ok why would you lean it out????stock jetting is 460 main and pilot 25....I have also a vforce with a fmf Q series silencer and a fmf fatty pipe....so almost same mods....let me know thanks

 

[yz125rider21]

also live in cali and at sea level

 

[adam728]

Big bore bikes often end up with leaner than stock jetting. The larger displacement pulls more air, creating more vacuum and higher air velocities at the carburetor. This means fuel is pulled through the jets faster.

 

[lwsmithjr]

This means fuel is pulled through the jets faster

.....thus a greater amount of fuel through the same size opening.

Adam is correct in most cases, however, in '05 a 420 main was stock. 2001 was the first year of the 38mm carb and Yamaha lost some of their coveted low end on the 125. Yamaha changed stock jetting (as well as other things) several times to get the low end back after going to the bigger carb. You can go to the Yamaha web site and look at stock settings for the various years.

KX250dad is running a 410 main in his '03 with good results. If I were you, I'd start at stock. If it blubbers (after it's warm) or smokes a lot, lean it out until it quits. Sometimes moving the needle is enough.

 

[KX250Dad]

410/40 Seems to be a bit on the slightly rich side @ 32:1 BelRay HR1 and pump gas, all else stock, that having been said had a chance to climb the tree just this past weekend and my son tells me not to touch a thing (he knows me all to well). Point being, great off throttle and can actually pull on many 250F's and that's what we were looking to do... now it's back to rider skill again. Note; of 45-50 bikes only 3 2T's... different is good if you can pilot a 2T and the EG144 gives a closer technology balance. We're somewhat above sea level in KY, and the outdoor ambient still hanging 44oF

Have fun...

 

[yz125rider21]

thanks for the help...friend works at yamaha is gonna dyno it...and I put results on here and go from there