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07 WR450F - Pilot air jet, Merge AP spring & CRF Apump kit questions


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24 replies to this topic
  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 23, 2016 - 03:37 PM


Been dealing with the dreaded off-idle bog with my WR450f.  Currently running the JD jet kit #168/red-4 needle, #48 pilot, #60 leak jet, & thick o-ring.  The previous owner was running the GTYR kit & needle.  Never checked the pilot air jet. Going to pull the subframe tonight to take a closer look & film the squirt, but I had a few questions that are still unanswered after searching the depths of the forum.

 

1. The 08 CRF450 apump kit.  I know the diaphragm has a shorter pin.  What other improvements does it have and how do they help?  Do these bikes need a longer acceleration pump squirt?  I remember when tuning my old 01 WR250F, the target range was 0.5-1 second - what's the target duration for the 450s?

 

2. If the gap between the AP set screw and AP link lever/throttle linkage at WOT is eliminated, is there a disadvantage to using safety wire vs buying the stiffer Merge AP spring?

 

3. The pilot air jet.  Stock 07 WR450F's come with a 70.  Stock 07 YZ450F's come with a 100.  The 07 Yamaha GTYR AIS removal kit came with a 110.  Which PAJ is the best to run, and how will it affect the pilot jet & fuel screw setting to run?  Does the GTYR AIS removal kit involve disabling the air cut valve (ACV) as well?

 

Most rides I do are 1000-5000 feet, 55-85 F.



  • Krannie McKranface
36,164 posts
Location: California
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Posted September 23, 2016 - 04:12 PM


All have been answered hundreds of times......

 

 

1. longer throw pump means a harder squirt, or a longer squirt, if you turn slower. The short pin requires a the long rod to make it work, hence the kit.

2. 1.0 full pressure squirt duration is your goal. The Merge or Tokyo mods spring is much smoother, and cannot bind or stretch, like oring or wire mods.

3.  If you have a YZ motor and YZ intake and exhaust, you use YZ jetting. You airbox, pipe, header, head, etc etc are all different from the YZ, so copying the YZ tuning exactly is not best

     Pilot jet size it chosen soley by fuel screw turns to reach highest idle. Less than one, it's too big. More than two it's too small. It's always a 45 unless you have worn out carb parts.

     The AIS has no effect on jetting, only the symptom of decel popping, which is eleviated with the ACV. Remove both and you need the 110 PAJ.....and it will still decel pop if in a low enough gear. Normal.



  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 23, 2016 - 04:23 PM


Ah.  I guess I'm still trying to wrap my head around why the GTYR AIS removal kit came with a 110 pilot air jet to replace the stock 70 PAJ WR's have?  Were you supposed to disable the ACV when installing the AIS removal kit?  The PO installed the AIS removal kit

 

And thanks for the extra info on the apump kit & spring.  I'm gonna order the honda apump kit & merge spring from the dealer.



  • Krannie McKranface
36,164 posts
Location: California
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Posted September 23, 2016 - 05:54 PM


The ACV requires the 70 pilot air jet.

The removed ACV requires the 110 Air jet.

 

...otherwise you will have to change the pilot jet....

 

Again, the AIS has no effect on jetting, just decel popping.



  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 23, 2016 - 06:48 PM


 

Again, the AIS has no effect on jetting, just decel popping.

 

Yes I understand that.  What I'm having trouble understanding is why Yamaha would include the 110 pilot jet in the AIS removal kit. 

 

Anyway, I pulled the subframe.  I have the 70 PAJ.

 

As for the pumper.  It is not hitting the slide.  And after quickly opening the throttle, I get what appears to not be anywhere near 1 second.

 

 

First twist (slow). squirt lasted 1 frame @ 29.895fps = .03345 seconds

Second twist squirt lasted 8 frames -> .26760 seconds

Third twist.  squirt lasted 8 frames -> .26760 seconds

fourth twist. squirt lasted 6 frames -> .20070 seconds

 

If the target is 1 second, that sure explains the bog! :)



  • Krannie McKranface
36,164 posts
Location: California
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Posted September 24, 2016 - 05:57 AM


Yes I understand that.  What I'm having trouble understanding is why Yamaha would include the 110 pilot jet in the AIS removal kit. 

 

Anyway, I pulled the subframe.  I have the 70 PAJ.

 

As for the pumper.  It is not hitting the slide.  And after quickly opening the throttle, I get what appears to not be anywhere near 1 second.

 

 

First twist (slow). squirt lasted 1 frame @ 29.895fps = .03345 seconds

Second twist squirt lasted 8 frames -> .26760 seconds

Third twist.  squirt lasted 8 frames -> .26760 seconds

fourth twist. squirt lasted 6 frames -> .20070 seconds

 

If the target is 1 second, that sure explains the bog! :)

 

Yes it does, more or less

 

You are either:

 

- short on fuel (leak jet is too big)

- short on pump (diaphragm is short thow + rod is short)

- soft on linkage (spring is stock)

 

...and/or a combination of all



  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 24, 2016 - 09:07 AM


Sweet.  Any differences in stiffness between the R&D spring, Tokyo Mods spring and the Merge racing spring?

 

Amazon has the tokyo mods spring so I'll grab that one if they're all the same - it would get here Tuesday.  Just in time to re-assemble and ride Fri :ride:



  • Krannie McKranface
36,164 posts
Location: California
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Posted September 24, 2016 - 10:41 AM


Sweet.  Any differences in stiffness between the R&D spring, Tokyo Mods spring and the Merge racing spring?

 

Amazon has the tokyo mods spring so I'll grab that one if they're all the same - it would get here Tuesday.  Just in time to re-assemble and ride Fri :ride:

 

In order of inscreased resistance (which in my opinion is what you want, more resistance)

 

Stock

 

R&D

Merge

Tokyo

 

....a subtle difference..



  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 27, 2016 - 07:13 PM


Ok.  Today I installed the tokyo spring, honda apump kit & #50 leak jet.  I have a bit work left to get a 1 second pump time.

 

It's lasting about .15-.30 seconds longer, so between .36 and .56.  In the video, some of the gas is oozing out of the AP, so I'm going to clean that again.  

 

The Honda's rod was the same size as my original rod.  However, the diaphragm pin was much shorter, and the spring provided was about 3mm longer (total length ~14mm).  I used the updated apump cover too, removing the check valve from my float bowl.

 

Attached Thumbnails

  • 20160927_181524.jpg


  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 27, 2016 - 11:07 PM


Well, after 4 hours of cleaning, and the result isn't any better :(

 



  • underground-mpyre

    TT Bronze Member

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Location: Indiana
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Posted September 28, 2016 - 04:13 AM


I am doing the same mod now. Do I need to go up to a #60 leak jet too on my 426? I was instructed in previous threads to get a 100 air jet, didn't say anything on a 110 air jet. Thoughts?



  • jamesm113

    TT Bronze Member

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Location: California
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Posted September 28, 2016 - 07:04 AM


Is your ACV enabled or disabled? The pilot air jet is unrelated to the pumper

  • underground-mpyre

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Location: Indiana
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Posted September 28, 2016 - 07:28 AM


Going to be disabled, filled with epoxy. Told me to go with a #100 air jet.

 

Do I need to get a #60 leak jet?



  • jamesm113

    TT Bronze Member

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Location: California
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Posted September 28, 2016 - 07:44 AM


A PAJ of 100 sounds right, but I've never owned the 426.

 

Leak jet depends on the volume of your squirt.  The smaller the leak jet, the bigger the volume of your squirt.  I'd suggest filming a few WOT twist's (like I did above) to time it.  You can count the # of frames the squirt is present, and that will tell you if your leak jet needs to be changed.  Luckily for you, it's a lot easier on your bike to pull the carb and change the leak jet than it is on mine  :smirk:   I also think the 426 carb is BK mod compatible.


Edited by jamesm113, September 28, 2016 - 07:46 AM.


  • underground-mpyre

    TT Bronze Member

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Location: Indiana
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Posted September 28, 2016 - 07:58 AM


BK mod?



  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 28, 2016 - 09:27 PM


Yea, the BK mod.  I gave you a link in my previous post  :)

 

 

Anyway, I'm starting to think my nozzle is not clogged.  Tonight, I've run about 4-5+ cans of carb clean, plus 100psi compressed of through a rubber tipped blow gun, and a used a copper speaker wire & small guitar string on the nozzle itself.  However, when bench testing the pumper, the results are still the same.  In the float bowl, I'm able to see plenty of light through the leak jet hole, check valve hole & passageway to the AP nozzle.

 

I'm able to get plenty of pressure through it.  This is what happens when I spray out of the nozzle:

 

 

 

https://www.youtube.com/watch?v=HLQEXtu-Dlo

 

What am I missing? I'm sure there's user error somewhere :(

 

I'm installing the diaphragm so that the letters face the AP cover



  • YZEtc

    TT Addict

3,579 posts
Location: Connecticut

Posted September 29, 2016 - 01:01 AM


Is there a one-way check valve in that float bowl that allows fuel into the acellerator pump chamber through that valve, but not flow backwards through it?


Edited by YZEtc, September 29, 2016 - 01:01 AM.


  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 29, 2016 - 07:02 AM


Yes, there is. I removed it to use the updated Honda pump cover though. The Honda pump cover has its own.

  • jamesm113

    TT Bronze Member

168 posts
Location: California
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Posted September 29, 2016 - 01:17 PM


An update, just in case anyone hasn't abandoned hope on this thread :)

 

I took it into a local shop, and after they did a bench test, we now suspect it's the timing screw.  I'll be experimenting with a few different ways to set the timing, including William1's method, the 07 YZ450f owner's manual method (1.25mm rod), the 07 wr450f owners' manual method (3.1mm rod) and JD Jetting's method.


Edited by jamesm113, September 29, 2016 - 01:18 PM.


  • Krannie McKranface
36,164 posts
Location: California
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Posted September 29, 2016 - 03:06 PM


Not the timing screw

 

 

It's the bowl cover or passage to the actual pump

I would try a very small leak jet and see if there is any change (smaller means more fuel).....and I'll bet there isn't much change,  because the fuel isn't making it over to the diaphragm






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