MotoUtah: Motocross and Off-Road Riding in Utah

Hi,
I bought this bike from Saint George this year from Tad. Thanks Tad! The jetting was set to:
165 main
N2ZJ needle at position 2.

I live at 4200 feet
I changed it to:
162 main
N2ZJ needle at position 2 (same)

It's a new bike for me, and I'm not really sure how it should feel. It sounds ok (no sputtering at mid throttle). However, I'm used to my 380 exc. It seems to have more mid range (and less top end). I'm interested in what others may be running at around 4000 - 5000 feet.

I think you're going to find that there is no perfect setup and many differing opinions on this matter, but I think you're close.
I've got an 09 300 and this is what I'm running..
Currently;
165 MJ
N2ZJ clip #2
38 PJ
Switching to;
162 MJ
N2ZJ #2
35 PJ
I've also have my slide modified to a #8 from the standard #7, got it done at Full throttle, which they will do for free.
I've also just sent my head off to Slavens racing for some trimming which may affect jetting but I understand it does not, we'll see.

Thanks. I'll probably play around with it a bit, but taking the carb out was difficult. I guess I should take off the tank or something.

Yes pull the seat and the tank, makes it much easier. You don't need to pull the carb to change the jets though. Once the seat and tank are off, then just pull the slide out and twist the carb to gain access to the drain plug. Once you get that off you can change the main and the pilot from there in a few seconds. Then you also have access to the needle for adjustment before you put it all back together. I too wish it were more simple than that, but hey it could be worse, try doing it on a WR450........... ugh

Andy wrote:


3 bolts will make your life a lot easier. also last time i pulled mine i pulled the bottom subframe bolts and just rotated it up and I could've had a party with all the room I had...

Wrfrk wrote:


That makes me laugh. I had an affair with a WR450 between my 525 and my current 300. I changed the jetting....once. I swore if I ever had to do it again I would sell it. I sold the bike

Actually there are a lot of things I loved about that bike, but accessing the carb was not one of them.

With the 300, seat and tank, a quick turn of the carb and you've got full access. Just takes a few minutes. My jetting is similar to what has been mentioned. I adjust the main jet by a step or two either direction during summer and winter riding, and maybe the needle one clib, but otherwise it still runs great and with no complaints.

I set my 300xc up for Mesquite in Feb by the owner's manual. 2000 ft and 60+ F

Ran the same in St. George with no issues, figuring I'd be changing it for Knolls; as it turned out the weather was so cold that I left it alone for Knolls!! (It ran REAL strong in the mid-range. I'm guessing it was too rich on top, but that can't hurt when you're riding full throttle on the mud flats.)

Kind of crazy! I am sure hoping that I WILL HAVE TO re-jet before the Firebirds race!

One word of caution to anyone trying to jet a bike with an FMF Turbine Core Spark arrestor. Mine (on an 08 250 XCW) had a manufacturing defect where the perforated core ended too close to the cone on the turbine. It got choked off with carbon deposits and the only place to breathe was the perforations in the core. That also eventually became choked off. All the jetting in the world won't make your bike run good if you have this problem with your silencer. Believe me, I tried. The fix? Cut 1/2" off the length of your core.

158 Main
N2ZJ #3
35 PJ
AS 2 turns out

I have the full Slavens Mule mods. Not sure if that effects the jetting or not.

Thanks for the tips. Anything to save time is great for me! I really only road this bike about 25 miles before racing it at Knolls. Turns out it ran well during the race, but there seemed to be a dead spot (only occasionally) and it would almost stall. This happened a few times when I was warming up the bike before the start. It happened as I was going from 0 to about 1/3 throttle. The bike almost stalled. It wasn't under any kind of load. I didn't notice it at all during the race. Of course I wasn't often at 0-1/3 throttle. My pilot jet is 35. I'll have to check that FMF spark arrestor thing. I think that's the one I have.

Thanks again.

The trouble is my 300 runs so strong its hard to tell a difference when jetting it. I left a rag in the airbox once and took 1st OA Am!...