2004 450F MAIN JET MIX UP

My 2004 YZ450 CAME WITH A 172 MAIN. MY 2003 HAD A 165. BOTH MANUALS SAY 165. DID SOMEONE JUST GRAB A 172 'CAUSE THEY WERE IN A HURRY, OR IS THE MANUAL WRONG? ANYONE ELSE CHECK THERE'S LATELY?

MY BIKE LIKES TO STALL IN TIGHT CORNERS. DOES ADJUSTING THE FUEL SCREW HELP? OTHER OPTION ARE A 49 TOOTH REAR, ACCELERATOR PUMP ADJUSTMENT?

HELP

I would go back to the 165 main and check the screw to make sure it's spec.

Mine came with a 165

Turn up your idle a little higher than normal and it will prevent stalling, as well as getting the fuel screw right. I put a power-now on mine, and it starts easier, and has more punch off the bottom. I'm at 7000 feet altitude so very different jetting up here.

Did you purchase you bike from canada?

they come with a 42 pilot and 172 main

jetnurse

You are a smart man.

I actually threw in a 170 yesterday and backed up the cam on my accelerator pump by 1/4 turn. I have the Jardine RT4 pipe and they recommend going up a size on the main. On my 2003 it came with a 165 and I went to 168. Now, my 2004 comes with a 172 and I went to 170. Were there carb/motor changes that warranted Yamaha going up 7 jet sizes?

Thanks for your help. :thumbsup:

Salut!The manual say a 42 pilot, 4th clip on the needle and 165 main, just like my 2003, but when I checked my 2004 it had a 45 pilot, 3rd clip on the needle and 175 main.

I didn't run it stock, but with my ported head, Hindle exhaust, GYTR flywheel and running Pro Racing Fuel MK IV, I run a 48 pilot, 4th clip and a 178 main.

With the same set up on my 2003 I ran 42 pilot, 5th clip and 165 main. The 2004 run quite a bit better, it's crisper and doesn't stall easily.

Ciao!

Guy

Hey...I was out there last Sep and really loved your province. Great people, great scenery and awesome MX tracks.

Did you have a bog, or stall off idle under load (like a heavy acceleration out of a corner)? I did. I went from the stock 172 to a 170. I haven't ridden it much yet with the new jet. The manual says try a smaller main if you have that bog/stall problem. If that doesn't work I'm going 48 & 175.

Vet28 :thumbsup:

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