Looking for the right thread

I just bought a 2009 KLX250SF. It has a Big Gun Evo R Exhaust. I took the elbow shaped snorkel off the air intake, but it still has the lid. Bought a Mikuni TM36-68.Other than that everything is the same. My problem is I can't figure out the carb. It always has backfired since putting it on. I'm not a mechanic. It came with a #130 Main, #12.5 Pilot. but when I hooked it up, the header pipe turned red. I understand that this is because it was so lean it made it extremely hot. I took out the #12.5 and put in a #17.5. Ran it for about 5 miles and turned back. Checked the spark plug, still grey. I tried to make it richer by moving the needle clip all the way to the bottom. I'm in Syracuse, NY which is sea level. I have no idea what to do. There's probably a threat already for this but I haven't been able to find it. Sorry if this thread has to be moved somewhere else. I just on a tight salary and I can't be throwing money into parts when I don't know if they will work or not.

Forgot to stress it's still a 250cc, I do not have a big bore kit.

Edited by tay675
Important Information

I have the Mikuni 36-68 on a KLX300 with no lid on the air box and an aftermarket header. This is how I have it jetted:

Main Jet 130

Pilot jet 15

Needle Jet 568-P8

Needle 9DZK6-50

Clip in middle slot

Float Height 20mm at highest point.

The pilot jet will only affect idle to about quarter throttle. If it is back firing on decelleration, try adjusting your idle mixture screw. With the engine warmed up, set the mixture screw for max idle speed. If the idle mixture screw is out more than 3 1/2 turns, go to a bigger pilot jet. If the idle mixture scew is out less than 1 turn, go to a smaller pilot jet.

How does it run from mid to open throttle?

Ride on

Brewster

It will hesitate if I hit the throttle to much. Power just isn't there. I think the word bog is used to describe it.

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