carb jetting issues
 

hey guys i need some pointers on my TM150 xrx carb. it has the 24mm.
my mods are gutted exhaust, and UNI intake filter inside of the original elclosed airbox. i have also drilled 3 1/8un. holes in the rear of the box.
inside of the carb was originaly a 114 main & 35 pilot. i stepped up to a 126 main and 38 pilot. with the results of the spark plug showing it was running lean (after numerous 10 min rides from 1/2 throttle to full) and going back and forth with the air screw also. soooo.....i stepped up the main to a 130.....with the same results. it still shows it is lean and for the life of me i cannot get the spark plug to turn tan.
i am also consused as to whether i am leaning it out or richening it because the pilot jet is located directly "beside" the main jet......i have been told if it is on the intake side and you srew it out you are 'leaning it" and if the pilot is on the air filter side you screw it out to "richen it" can anyone help me with this? this is jetting thing is taking away from some much needed off road fun:dunno:

Same boat
 

I am in the same boat. Luckily i am having a guy across the street look at it tomorrow. After doing all the work to mine i couldnt even get it to start without adjusting the air and fuel screws both. Just when i thought i had it working good, the plug was black and rich. I dont believe you will need a 130 but i could be wrong. I am hoping the dirtbike-master across the street can get it tuned in for me good so i don't have to take it elsewhere. I have read multiple reports on which way to turn the screw to lean it out or to richen it. By the way, did you have to cut the tops off of your rivet/bolts to take the bowl off of your carb? Or did you have regular phillips head bolts in there?

Why are you still using the restrictive stock air box?

The 130 main should be enough. But are you making WOT runs and shutting it down right away? THEN checking the plug?

Does your carb have an adjustable needle?

Not sure which way is rich on yours, but use a tachometer to help dial it in. Idle it around 1100 RPM and adjust the idle screw 1/4 turn in or out until you reach your maximum RPM.

USUALLY if you're more than 2 turns OUT, you need to go down 1 on the pilot jet. If you're less than 1 turn out, you need to fatten up the pilot jet. Ideal is 1 1/2 turns out.

xlint89, im using the restrictive air box which i have drilled the holes in, due to my usual climate. the trails i will be riding down are mostly always wet with mud. and i dont want to constantly clean my air filter of mud specks. yep.WOT kill it and check it. no adjustable needle, but i am using small washers that fit snug around the needle to raise it to the desired positions. im taking it to my buddys tomorrow. he has his own atv biz. so ill just throw his a few bucks since im stumped. ill also "WATCH AND LEARN".lol