Hey everyone. VERY long time, no see.

I'll cut straight to the beef. I have a big bonus coming my way at work, and I'm going to buy the Muzzy full exhaust for my 09 KLX250S. Currently I have the DJ "Stage 2" kit... 128 main and I'm pretty sure the needle in the 3rd clip. Snorkel removed. I ride at low altitude (sea level to 300 feet). Bike runs great as is, but I'm wondering if I should go up one more size on the main when I install the exhaust. I will run the exhaust with the quiet core and spark arrestor, if that makes a difference. What about the fuel screw? I'm about 2.5 turns back out from fully seated (per the kit's recommendation). Am I going to need to adjust the fuel screw a bunch or should I move the needle?

I know this is a lot of very specific jetting questions. I'm just concerned with burning up my motor by running it too lean.The DJ kit came with a 132 main as the next one up, which is what I'm leaning to installing, but waiting for people who are smarter (you guys) to chime in.

Thanks in advance.

-Cliff

 

I have that exhaust system. It's only really going effect the needle and main jet requirements at most. You probably shouldn't see any effect in the pilot or idle adjustments. When I ran the OEM carb, I ran the same main and DJ needle position that you have. I live at 1700' elevation. Don't try using the air/fuel screw adjustment to affect what might be a needle raising requirement. It just won't get the job done. Another big factor on the needle and main requirements will be your airbox configuration. Mine is run with the backfire screen removed and a nearly wide open airbox lid. This is a notable factor from mid-range to full throttle with a good exhaust. You get a notably reduced effect from a full performance exhaust without letting more air in...especially as you go up in displacement.

It's not the only good performance exhaust system out there by any means, but the full Muzzy really works. It's super durable too. Mine has been totally trouble-free. I've also crashed bunches of time on the right side, and I'm always amazed how it takes that punishment.

 

OK I dug out my DJ kit to confirm some things. DJ's instructions recommend a 124 main with the snorkel removed stock exhaust, 128 main with snorkel removed and aftermarket exhaust. I currently have snorkel removed, stock exhaust, with their 128 main, and the bike runs great.

I tried removing the airbox lid once, and even with the stock exhaust and 128 main, the bike didn't run great (kinda a delay in power when rolling on the throttle). So based on that, I think I'm pretty dang close to perfect as the bike is currently set up.

So if the main jet is good to go, maybe I should just raise the needle one notch?

 

I wouldn't change anything at first and only pull the carb if you feel you need to, you might not need much or anything at all.

 

Agreed. You should "carefully" drive the bike a little just as it is after the exhaust. Feel for flat spots or hesitation which should all be signs of leaness in your case. Just don't lay on the throttle for a long period until you're sure you're not too lean. You know why.

 

Hi. I ran a full Muzzy with DJ's stage 2 rec's, 128 main and 3rd notch. Airbox lid removed and aftermarket air filter. These settings worked perfectly for me. When I switched to a 330 the only change required was 132 main to give enough gas over 7K. Only potential change would be to raise the needle one notch - but it would be to experiment, not because of poor performance.

I like the Muzzy - looks and sounds great - the only caveat is the cannister mount point on the bike is too weak. The original attachment point let go fairly quickly, a re-weld lasted only a month or so, and the final fix was a 3 inch plate welded to the bike's rail with the nut welded to the back of the plate. The Muzzy only uses one of the frame's two cannister mounting points and I think the springs put additional stress on the single connection. Also the cannister has a tendency to vibrate lose so be sure to use a lock washer and blue locktite.

Hope this helps.

 

Agree on the weak muffler subframe bracket. Instead of welding, I cut off the old, broken subframe tab and made a heavy duty aluminum bracket that spans across 2 of the bigger bolts that are on the subframe. The aluminum bracket is made out of 1/8th thick aluminum, so it's easy to cut, shape, and drill. It's been on there since 2009 without any issue of cracking or failing.

 

well im at the same as you are and 132 worked just fine

 

Zippets, your sig line has a mukuni listed, I think the op has the stock CV so it's a little apples and oranges on that one unless you went back to stock.

 

Dude what do you think i had before the Mukuni ???