2004 YZ450F jetting question

bents
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5/17/2020 7:30am Edited Date/Time 5/17/2020 3:45pm
So I posted about a year ago that I picked up this minty 450, and hadn't done a thing with it since! I finally brought it out of mothballs and threw 2 new tires on it, a new air filter, changed the oil, and installed a Pro Circuit slip on I picked up cheap just for shits and giggles. Fresh gas. Tons of compression. Here is my question-my jetting seems to be a little off and could this be because of the slip on?

Took it out to the track to run a few laps yesterday and took it easy (the fork seals are leaking but I did the usual temporary fix for the day), and it ran pretty dang good aside from just a little hiccup. Any thoughts on the jetting by anyone? I will say that the motor is what I remember from my 2003-tons of torque, meaty, and pretty dang quick. My regular ride is a 2018 FC350, and this will be a nice compliment to that bike. Fun fact-this 450 weighs the same as my 350! Anyway, it will be a fun bike and nice change from the 350. The forks need a rebuild badly, and I still need to give it a good once over otherwise. Any advice on set up or this jetting query would be appreciated.
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Racer16
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5/17/2020 8:22am
Do you what jets are in it? Pull the carb apart and tell me what’s in there and I’ll set you up with some jetting specs
bents
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5/17/2020 10:56am
Racer16 wrote:
Do you what jets are in it? Pull the carb apart and tell me what’s in there and I’ll set you up with some jetting specs
I assume it is stock and I have the manual-if it is indeed stock, I would appreciate any specs you have. I am at sea level. Thanks a bunch Racer16.
bents
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5/17/2020 11:06am
Racer16,

Main-172
needle-OBEMR-3rd clip
Pilot-45


Racer16
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5/17/2020 11:55am
bents wrote:
Racer16,

Main-172
needle-OBEMR-3rd clip
Pilot-45


That should be about right. Try disassembling carburetor and cleaning all jets and passageways. If it’s pooping then might be a lil lean. Try 48 pilot jet. You didn’t mention how many turns out you have the fuel screw at. Screw it all the way in til it lightly seated. Then turn out 1 1/2 to 2 turns out. Adjust the screw with the bike running and turn the idle down til it just barely runs. Then go out on the fuel screw. You’ll hear the idle start to climb. Once it stops climbing stop turning the fuel screw out. Try turning the throttle and seeing how it picks up and responds. You may have to try adjusting the fuel screw more or less depending on altitude and other factors. Hope this helps👍🏼

The Shop

bents
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5/17/2020 1:26pm
Beauty thanks a bunch and will let you know how it goes.
#434
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5/17/2020 3:45pm
Clean the accelerator pump and make sure that it works.
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yz133rider
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5/17/2020 7:20pm
One step larger pilot will clean it right up in my experience.

Just replace it, order a new 45 and a 48. Toss the 48 and see what you think.a fresh pilot is where i always start tho as they get plugged up and never run right again.
bents
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5/18/2020 9:17am
Thanks YZ133-good advice.

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