I have an '09. The bike was originally from Golden, CO, but I bought it in Indiana. Most of the normal mods were done when I bought the bike.
It had an FMF Q4, DJ kit and had been de-snorkeled. The PO gave me the DJ kit and it had notes that the Main was #128 and the fuel screw was 3 turns out.
It had a very slight stumble at WOT, but otherwise ran great.

I did not like the FMF--way too loud for my taste. I put an OEM pipe off a '13 on the bike and it ran fine, though it still had the slight stumble. Still a lot of intake noise. Sort of rrrrrrrr huh rrrrr feel to it at WOT.

I read a thread where someone claimed that adding a KDX snorkel solved a similar issue, so I installed one. Very marginally better, but the intake noise is greatly reduced.

Noticed a drop off on the top speed. Maybe 64 mph (GPS indicated--speedometer doing its usual 10% incorrect thing.)

Any thoughts on the current jetting setup? Any recommend changes? The original owner was running a 122.5 with the fuel screw at 2.5 turns while in CO.

I have not done any plug chops to see what the plug looks like and it's a bit cold to do it at present.

Thanks for any help

 

Model and year of bike, PLEASE.

Ride on
Brewster

 

Sorry, 09 KLX 250S

 

If I remember correctly, the 128 DJ jet is their 'Stage 2' setup for aftermarket exhausts. With a stock exhaust, you might try dropping it down to the 'Stage 1' jet and needle settings. (I don't remember what they were.. I'll try to find the docs that came with my kit when I get a chance.)

As for the stumble.. I still have a stumble under load around 5500 rpm at times on my '09. Not enough to worry about, but it is still there on occasion. Some folks have had luck getting rid of it by adding extra grounding.

Also... this may help: KLX250s Jetting Spreadsheet

 

Thank you!