2009 YZ450F Carb settings?

Honda11
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252
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Location
Inside, KY US
3/8/2017 4:41pm
So I finally got my bike running (kinda). The bike is very hard to start, once it finally starts it idles steady, but very high. There are two adjuster screws on the carb, one coming straight out of the bottom of the bowl, and the other is right above the bowl on the left side. I believe one is air and one is fuel? The header also turns glowing red within a minute or so of idling at the high speed (which may be normal?)

Does anyone know the stock settings for the two screws? I have downloaded a service manual, but it is very complicated compared to my manual for my CR250 lol. My CR had a carb setting chart that I could follow (for altitute, temp, etc.) but the YZ manual doesnt seem to have something like this.

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speed_racer
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Aiea, HI US
Fantasy
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3/9/2017 7:35am Edited Date/Time 3/9/2017 7:52am
Much experience tuning that bike with an exhaust gas analyzer.

I am only talking low speed jetting here, this is what I found out about those bikes.

The stock pilot jet is way to lean, I've had to go as high as 55 pilot jet at 2.5 turns with the mixture screw.
This seemed rich in my head, but they start and idle great and the EGA machine reads 2.8% CO 150HC, excellent numbers and they purr at those settings, again I would think it's to rich but the machine backs up my ears.

When it sounds right, and the idle is like a rock, and the EGA backs up the healthy idle, you have figured it out, and for that bike I had to go from a 48 pilot to a 55, that is a huge jump, but it made the bike start and idle, after fixing 3 of them others could not I stopped second guessing myself and now know they are lean as the years go by, not sure why, but back in 2009 we were using 50 pilot and getting the good EGA settings, why they need such bigger pilot is confusing, but the digital EGA doesn't lie.

I think part of it is the shit fuel isn't any good, causing a bigger jet to actually get some fuel because of so much byproduct taking up the space the fuel should be sitting in.

Try the 52 first and see if it's way better, but if it still has an erratic idle and won't stay consistent try the 55.

A totally different motorcycle after proper EGA tune, idle perfect and rev with no hesitation, and the backfire goes away.

After the 55 is installed be prepared to have to lower the idle adjustment, this is a good thing, right now you have the slide open way to far to get it to idle, a sign of lean condition.

Same thing for the KTM 525,530

IMPORTANT:
When tuning those I use a huge fan pointed at the front of the engine. Never run that engine sitting on the stand without airflow for very long, it can melt the top end, it needs air cooling it off. I run them for 20 minutes but always use a huge fan.
Honda11
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252
Joined
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Location
Inside, KY US
3/9/2017 2:35pm
Much experience tuning that bike with an exhaust gas analyzer. I am only talking low speed jetting here, this is what I found out about those...
Much experience tuning that bike with an exhaust gas analyzer.

I am only talking low speed jetting here, this is what I found out about those bikes.

The stock pilot jet is way to lean, I've had to go as high as 55 pilot jet at 2.5 turns with the mixture screw.
This seemed rich in my head, but they start and idle great and the EGA machine reads 2.8% CO 150HC, excellent numbers and they purr at those settings, again I would think it's to rich but the machine backs up my ears.

When it sounds right, and the idle is like a rock, and the EGA backs up the healthy idle, you have figured it out, and for that bike I had to go from a 48 pilot to a 55, that is a huge jump, but it made the bike start and idle, after fixing 3 of them others could not I stopped second guessing myself and now know they are lean as the years go by, not sure why, but back in 2009 we were using 50 pilot and getting the good EGA settings, why they need such bigger pilot is confusing, but the digital EGA doesn't lie.

I think part of it is the shit fuel isn't any good, causing a bigger jet to actually get some fuel because of so much byproduct taking up the space the fuel should be sitting in.

Try the 52 first and see if it's way better, but if it still has an erratic idle and won't stay consistent try the 55.

A totally different motorcycle after proper EGA tune, idle perfect and rev with no hesitation, and the backfire goes away.

After the 55 is installed be prepared to have to lower the idle adjustment, this is a good thing, right now you have the slide open way to far to get it to idle, a sign of lean condition.

Same thing for the KTM 525,530

IMPORTANT:
When tuning those I use a huge fan pointed at the front of the engine. Never run that engine sitting on the stand without airflow for very long, it can melt the top end, it needs air cooling it off. I run them for 20 minutes but always use a huge fan.
Thanks for the tips, I do not have an EGA, and after a quick search online, I don't think I'll be getting one anytime soon either lol.

But, I will start with checking the jets. I purchased the bike from a different state, so its probably off for my location anyway. Once the bike starts, the idle is very consistent and crisp, but its idling around 4-5k RPMs (by guess) Could jetting cause a high idle? Or should I look somewhere else?

I've never thought about the fan idea, sounds like a good idea!
Paw Paw 271
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Benton, LA US
3/9/2017 4:01pm Edited Date/Time 3/9/2017 4:01pm
The screw on the side is for idle speed. CCW will lower the idle speed.
The screw under the carb is the fuel screw. CW leans the fuel mix and CCW richens it. This needs to be reset regularly with the change in weather. A good starting point is about 2 turns out from fully seated. This effects the entire rpm range.
These bike came jetted for altitudes of sea level up to about 3,000 feet, so the OEM jetting should work unless you are in the mountains.

Paw Paw
Honda11
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Inside, KY US
3/9/2017 4:57pm
Thanks, thats pretty much the exact info I needed. I am in low elevations, under 1000 feet always.

Tonight I believe I got the bike pretty close to idling right. I had the fuel screw out between 1.5-2.5 turns (adjusting back and forth) and the idle screw about 2.5 turns out. As I adjusted the idle screw, it wouldn't change very much at all until all at once the bike would die, usually at about 4-5 turns out.

The only Jet I could remove without removing the carb (or at least removing the clamps on each side) was the main jet, which is a 162. According to the manual, stock should be 160. Would this make much of a difference/problem?

The Shop

Paw Paw 271
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3/9/2017 5:51pm
The main should be ok.
You can also remove the pilot jet through the same hole in the bowl. If clogged or partially clogged it will effect idle and starting.

Paw Paw
Honda11
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Inside, KY US
3/12/2017 3:43pm
The main should be ok. You can also remove the pilot jet through the same hole in the bowl. If clogged or partially clogged it will...
The main should be ok.
You can also remove the pilot jet through the same hole in the bowl. If clogged or partially clogged it will effect idle and starting.

Paw Paw
Today was the first day I was able to get it to the track and try it out. I think I got the carb adjusted right, starts first or second kick usually (hot or cold) and seems to idle fine and it seems crisp with no hesitation.

My only problem is, sometimes when coming into a slow corner, or idling around in first gear, the bike will die. Almost like it just runs out of gas. Sometimes itll fire back up first kick and be fine for a few more laps. Sometimes it will take a few kicks to get it to start back up. And sometimes it'll fire right back up but die right away and i'll have to kick it 4 or 5 more times before it fires up and will be fine for a few more laps.

It seems to be an intermittent problem which has me confused on where to start looking.
Paw Paw 271
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3/12/2017 6:00pm
The bike may be loading up ( flooding) under low load and low rpms. That is not all that unusual, but it can be helped with leaning the fuel screw about 1/4 turn CW. If that does not help, then you may have to check the float height.
In any case, when this happens, be sure to use the hot start lever when restarting a stalled engine. What it does is lean out the fuel mix for easier starting. You may also want to idle it up just a bit. Remember that these bike are ment for all out racing and not for putting around.

Paw Paw

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