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Jetting for higher elevation

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2011 WR450. Snorkle removed. AIS removed with GYTR kit. Aftermarket pipe.

I recently moved to the mountains in the west, and bumped my low elevation starting point from 200' to 3000'. The humidity is typically in the teens around here, much nicer than the 100% around the east coast. Temperature is fairly similar in both locations.

I have been trying to set my pilot per the sticky instruction thread, but can't get the motor to die when I turn in the fuel screw. I dropped the pilot from 52 to 45, but the engine speed doesn't seem affected when turning in the fuel screw. And it only starts to sputter when I turn it out 4 turns or so. How small of a pilot should I need to go at 3000' elevation?

I also dropped the needle (NCVS) from 4th to 3rd clip, and the main from 168 to 162.  Do you think this is enough?

Most of the time I'll be riding between 3-6000' elevation, which is where I want to dial in. I'll be riding up to 8-10,000'+ elevation at times, but will adjust for that when needed.

Thanks in advance!

Edited by jimmym

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You have a ACV and altered jetting to match on that carb, stock.

Until you elminate the the ACV, you get vauge fuel screw results.

You remove the floating piston inside, block all the holes off with a home made gasket, and change to a 100 pilot air jet.

You need a 45 pilot for up to 8000, and maybe a 42 for higher up.

There is no situation that requires a 52 pilot jet that is not based on something else being wrong.

 

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I'm not sure why, but I've never heard of the ACV before. Searching on it I find a ton of references, but I still have two questions:

  1. Looking at the following carb diagram, is item #21 the pilot air jet?  
  2. I can't tell where this jet is located from the diagram, but it looks like it screws into the intake side of the carb. Please don't tell me that I need to take this carb off again. I have yet to find a simple way to get this thing back together with the aluminum frame, and it may be the only maintenance item I absolutely dread.
Edited by jimmym

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I found the answer on a youtube video. It's strange that the parts diagram lists the Pilot Air Jet as Jet, Main. I guess it makes sense, but there's certainly room for confusion. I'm ordering it now.

 

 

 

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I posted this a while back and have been very happy with the following setup on my 2007

 

2007 WR450F (Riding Elevation 5000~9000 Feet / AVG Temp 55~85ºF / AVG Humidity ~45%)

 

Completed Mods:

Grey Wire

AIS Removed

Air Box Mod

Throttle Stop Screw replaced

Exhaust mod via GYTR Replacement End Cap

Accelerator Pump Mod

TPS is connected, but I would like to make a switch to turn it on and off.  ON for trail and single track / OFF for longer highways stretches.

 

I decided on the following for a starting point:

Main Jet: Stock is #168 / Change to #160 (4MX-14943-39-00)

Pilot Jet: Stock is #45 / Keep Stock #45 (4MX-14948-05-00)

Leak Jet: Stock is #60 / Change to #50 (4JT-1494F-07-00)

Starter Jet: Stock is #65 / Change to #68 (3TJ-1494F-14-00)

Needle Model/Clip position: Stock is NFNT / Change to NCVS 3rd clip down. (5TA-14916-VS-00)

Pilot Air Jet: Stock is #70 / Change to #110

You use a 70 pilot air jet when the carb's ACV valve is intact and working

You use a 100 or 110 when it is blocked off (like on a YZ, which has the ACV valve cast shut) 5TA-14943-27-00 = #100 P.A.J. from the '07 YZ450

 

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I fashioned a couple of rubber gaskets to block the ACV ports. They aren't perfect but they work nicely. See below.

The Pilot Air Jet #100 is on backorder and I won't see it for another week. I attempted to dial-in with the 70 PAJ, but the motor still won't die when I completely close off the fuel screw. I'm thinking about trying a #42 pilot jet while I wait for the PAJ. The temps here are about 90 degrees and 18% humidity @ 3000', so I'm surprised a #45 isn't working.

IMG_20170814_165024.jpg.62c3da9482d893e5eab4c1e7b80e8da5.jpg

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Three weeks later and my local shop still doesn't have the #100 PAJ I ordered. :thumbsdn:

I think I'll just order online and grab the #110 instead. I can't seem to find the part number for the 110 PAJ, does anyone have it handy?

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I was never able to find the OEM part number for the #110.  Been running the #100 for a long time and it's fine.

5TA-14943-27-00 = #100 P.A.J. from the '07 YZ450

RockyMountainATVMC has the #100 in stock for $5.12

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Thanks for the part number, I ordered the PAJ on Friday and it was delivered today. 

I installed the #100 PAJ and got everything else put together. I warmed her up good and attempted to dial in the fuel screw, here's the story:

  • Elevation: 3,000'
  • Weather: 99 degrees and 15% humidity
  • Main jet: 162
  • Pilot jet: 45
  • Needle: NCVS 3rd clip
  • Leak jet: 50
  • PAJ: 100
  • ACV blocked
  • AIS removed, airbox modded, aftermarket exhaust, short throttle stop screw 

I set the fuel screw to 2-1/4 turns, and the idle just enough to keep running:

  • I can turn the fuel screw all the way in and the engine doesn't die. In fact, the RPM actually increases the last half turn or so.
  • Turning the fuel screw out, the engine dies around 4 turns

Based on the sticky I should install a smaller pilot jet, but want to make sure I'm not missing anything before jumping in that direction.

Thanks

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With a hot motor:

Fuel screw at 1 turn out

Idle as low as it will go

Turn the fuel screw OUT to raise the idle. 

As soon as it stops going up, stop. Note that location.

Now, blip the throttle, and listen for the speed of the idle drop. You turn the fuel screw 1/8 in either direction and choose the fastest idle drop.

That is your final positon. 

Ignore the 'won't kill all in' and stuff like that. It's just a pilot trim on an old bike. All the brass carb parts, top end, and valve train would have to be brand new before those symptoms had any real meaning...

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With the fuel screw 1 turn out and idle set as low as it will go, the idle doesn't change when I continue to open the fuel screw. At least I can't hear any difference.

With the idle this low, wicking the throttle kills the motor regardless of where the fuel screw is set.

I raised the idle a bit until wicking the throttle didn't kill the motor, then tested blipping the throttle with the fuel screw set at various positions. 1-3/4 turns seems to be best setup for this test, but I would need to increase the idle a bit more to be able to wick in any situation without killing the motor.

Since I wasn't able to get it to work with your instructions, and my testing didn't follow your instructions, do you have any suggestions I should try?

 

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58 minutes ago, jimmym said:

With the fuel screw 1 turn out and idle set as low as it will go, the idle doesn't change when I continue to open the fuel screw. At least I can't hear any difference.

With the idle this low, wicking the throttle kills the motor regardless of where the fuel screw is set.

I raised the idle a bit until wicking the throttle didn't kill the motor, then tested blipping the throttle with the fuel screw set at various positions. 1-3/4 turns seems to be best setup for this test, but I would need to increase the idle a bit more to be able to wick in any situation without killing the motor.

Since I wasn't able to get it to work with your instructions, and my testing didn't follow your instructions, do you have any suggestions I should try?

 

Do you have a fresh emulsion tube, rings, and intake valve sealing ??

That's where you stand, pretty much.....it's gotta be new to act  new....

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Certainly makes sense. I don't have many hours on her, but she's running well again with the recent changes.

Thanks for all the help getting her to this point. I'll continue to get her dialed in, but I'll finally be able to get out and ride again now that the temperature has started to cool a bit.

Thanks!

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