I know there's info spread around here and there at KF but maybe someone with that combo can sum it up? (air box lid off)

I have the TM36 on and the 331 is on its way. Other than doing some WOT plugs chops to check the main jet, I think I'm good to go at 250cc with the big carb.



Just wondering how the extra 80cc is going to alter TM36/250 jetting

 

might not change much if at all.

im still on the stock 34mm carb but other than having to tune the pilot circuit a bit, no changes after my 331 install.

 

Stock pipe?

99 KLX300 (due for a valve job), stock cams, SX-1 pipe, TM36-68
Main - 128 to 132*
Pilot - 15* to 17.5
PAJ - 0.9 to 1.1*
* denotes current jets

Idle - 1350 to 1400rpm (no blip stall)

Don't remember the needle or needle jet, need to richen up 7/8 to WOT.

 

Mine's not a stock pipe. It has a larger OD on the header and the mid pipe expands megaphone-style. Shorter overall length than most KLX pipe's as well

Looks a lot like this one from DRC, though maybe a couple inches shorter to the end of the muffler



Megabomb header (made in China) will be here in a couple months

So far I've gone back to the 15pj and a 130mj but still waiting .. for clearer weather to do some plug chops. The 130 must be close cause there's no obvious issues at WOT

Still at 250cc though

 

You should be close after the BB. Some times jetting is a tad leaner, the explaination is the BB pulls more air and causes a richer mixture. Do have a few PAJ's (0.9 to 1.2) and PJ's on hand to tune the idle/lower 1/4 throttle range.

For sea level, 15 PJ & 1.1 PAJ is my current setting. Mild decel pop. Still fiddling with 3/4-WOT.

 

It's interesting that you have a 1.1 PAJ at sea level. That's leaner than stock if I understand the PAJ correctly. I had to go to a 0.9 PAJ to richen up the idle and just-off-idle response on my KLX with just a 300 cylinder. The PAJ works differently than the fuel based pilot jet because it yields a stronger vacuum signal to the pilot circuit by using a smaller PAJ. Initially that sounds cross-purpose, but it is true as you probably know. I had a small lean stumble on my initial setup with the 1.0 PAJ. I could have changed the pilot jet from 17.5 to 15.0 and probably achieve the same results, but the 0.9 PAJ gave me a perfect response. I'm at about 1700 feet. While jetting for each bike will/can have different needs based on a variety of factors, I would have anticipated your 331 at your altitude to use a no more lean requirement than the stock 1.0 PAJ and the 17.5 pilot fuel jet. Just goes to show how fine tuning by each user is still an important requirement.

Edit: Well, to add confusion to this discussion, I noticed I mentioned going from a 17.5 to a 15 pilot fuel jet would be the same as dropping from the 1.0 PAJ to a 0.9. It's the opposite. I would have had to go to a 20 pilot fuel jet to achieve the same result that I got by going to a 0.9 PAJ. The smaller PAJ delivers a richer pilot circuit.

 

Originally, my carb did not have a PAJ installed and the plug was always wet.

I'm still learning this carb, so any info is valued.

 

I know I have the .7 and .9

I'll keep your advice in mind after I get the 331 installed a few months from now

 

TNC

Thx for that edit, didn't know the PAJ was so effective.