FMF Q Stealth
 

I recently purchased an FMF Q stealth for my '08 EC 250. I was really concerned at first when I went riding, 'cause I actually forgot it was there. It is super quiet, which is nice, but frankly, it sounds the same to my ear as the stocker (which I was running because I ruined my FMF turbine core 2). If it wasn't for the stupid spark arrestor, there'd be no need to change.
Anyway, it's quiet, really quiet. However, while I was riding, I noticed my bike seemed really weak, and seemed to hesitate at low rpm and small throttle settings. Turns out the muffler affects the jetting. After playing with my airscrew all day, for two days I shouted out to Ron at RB designs for help. He had a few suggestions, but his first one was spot on. I was running a CEK needle in the #2 position, and he suggested I try a CEL needle in the #2 position. I did that, and now I'm happy to report that the bike runs just like it should off the bottom. I'm going to try his other suggestions for fun, as I'm chasing an unrelated pinging issue. He's trying to wean me off of race gas. I'll be running it through the Idaho qualifier just for safety, but after that, I'll look into going back to plainolegas.

where do you buy a cel needle from or for that matter any other needles , besides your dealer , is there an online place you could recommend ?

I get all carburetor related stuff from Ron at RB-Designs. More than the brass parts, his advice on jetting is well educated and quite helpful.

trying to wrap my head around this. an l needle is leaner than a k needle at 1/8 to 1/4 throttle openings isn't it? i would think you would go the other way around to get more fuel at small throttle openings...

True, the L needle is ever so slightly leaner, only in the straight part of the needle, for those small throttle openings.

The theory, as posed by Ron Black of RB Designs is that the big fat muffler is cooling the expansion chamber too much making the burn less efficient, thus requiring leaner jetting for the first portion of the throttle.

It seems to be good thinking, because the moment I changed the needle, it ran like it used to.

I hated that POS turbine silencer, that thing plain "SUCKED" !!!!
What ever the spring loaded gizmo in silencer was kept getting stuck open and the bike would get loud and run poorly.
I was constantly stopping on the side of the trail and wringing the throttle while covering the end with my glove....the only way I could get it to re-set.
So,
I just switched to the stealth, I only have one ride on it so far and no problems or complaints as of yet.

I didn't need any adjustments to jetting or airscrew. It just works fine with
"new style" GG-pipe and Q-stealth.