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2004 450F MAIN JET MIX UP

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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

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

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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.

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Did you purchase you bike from canada?

they come with a 42 pilot and 172 main

jetnurse

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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:

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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

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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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