2008 WR450F WITH YZ SUSPENSION AND CAMS / PART DEUX

Yamaha YZ450F 2008

132 replies to this topic
  • Krannie McKranface

Posted July 21, 2013 - 09:16 AM

#1

........fixed it.........

OK, let's all learn together:

This is a stock FCR CR Needle jet (emulsion tube) (main jet shown attached): No part number, no 'jet' number. No holes.

Posted Image

The one inside that was originally inside my carb, is on the left. Corroded, and ovaled, and needed to be replaced.
The one on the right is [size=4]a 'Factory 150" 8 hole perforated Needle jet: supposedly the exact same as stock, but with emulsion holes.[/size]
[size=4]That is what I replaced the stock one with. The picture makes them look different in size. They are the same.....don't know why they look so different in the pic.[/size]

Posted Image

Results? Chasing a gremlin for a month+, trying to figure out why at 1/16 -1/8 throttle, there was a massive flat spot.

Turns out, the Factory 150 Needle jet was wrong. Don't know why it was wrong, but when i changed to a 16 hole genuine Keihin Needle jet, everything went back to normal.

Posted Image

This is the Needle Jet I have used before, and thought the the Factory 150 was the same. WRONG.
This comes out of the 2002 WR250F as a stock carb part. It has 16 emulsion holes.
I came across this part when trying to tune a friends FCR carb on a DRZ400. This fixed his flat spot problem.
Essentially, what it does is atomize the fuel sooner, and better, for better partial throttle control.
Using a stock WR450 carb part probably would have worked too....but not quite as well.

Well, that only took two months.................

  • Krannie McKranface

Posted July 21, 2013 - 09:24 AM

#2

I just found a post about someone else trying the same Factory Pro needle jet and having the same flat spot problem I had.............

Apparently they just were all made wrong, and actually don't even work very well.

Oh well..........

  • Krannie McKranface

Posted July 21, 2013 - 09:26 AM

#3

So, now the power is back to normal, with more over rev and power on top (yz spec hot cams for wr).
Power off-idle is just like stock. You are able to grunt down low, keep it there or run it up to more power, with no hiccups, shelves, or issues.

OK, so NOW would I do it all over again, with the hot cams???


...maybe....

  • Krannie McKranface

Posted July 21, 2013 - 01:58 PM

#4

[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]"I just took mine out for a 25 mile dual sport ride, after spending a month chasing issues. My issues was not the decomp pin, mine was fine. It was a bad Needle jet.[/background][/font][/color]
[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]I have a very quiet slip on mounted now, so the top end power is down a little bit, but the power overall is very good. Very [/background][/font][/color]smooth[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)], easy normal power at small throttle openings, and some serious pull from the mid rpm's up with a tug on the throttle."[/background][/font][/color]

[color=#282828][font=helvetica, arial, sans-serif][background=rgb(252, 252, 252)]-from another post[/background][/font][/color]

  • stevethe

Posted July 21, 2013 - 06:59 PM

#5

........fixed it.........

OK, let's all learn together:

This is a stock FCR CR Needle jet (emulsion tube) (main jet shown attached): No part number, no 'jet' number. No holes.

Posted Image

The one inside that was originally inside my carb, is on the left. Corroded, and ovaled, and needed to be replaced.
The one on the right is [size=4]a 'Factory 150" 8 hole perforated Needle jet: supposedly the exact same as stock, but with emulsion holes.[/size]
[size=4]That is what I replaced the stock one with. The picture makes them look different in size. They are the same.....don't know why they look so different in the pic.[/size]

Posted Image

Results? Chasing a gremlin for a month+, trying to figure out why at 1/16 -1/8 throttle, there was a massive flat spot.

Turns out, the Factory 150 Needle jet was wrong. Don't know why it was wrong, but when i changed to a 16 hole genuine Keihin Needle jet, everything went back to normal.

Posted Image

This is the Needle Jet I have used before, and thought the the Factory 150 was the same. WRONG.
This comes out of the 2002 WR250F as a stock carb part. It has 16 emulsion holes.
I came across this part when trying to tune a friends FCR carb on a DRZ400. This fixed his flat spot problem.
Essentially, what it does is atomize the fuel sooner, and better, for better partial throttle control.
Using a stock WR450 carb part probably would have worked too....but not quite as well.

Well, that only took two months.................


Surprised a wr250 part would work. Different needle jets are even listed between a 08' yz450 and a wr450.

  • beezer

Posted July 22, 2013 - 09:28 AM

#6

Glad you found the problem.

  • Krannie McKranface

Posted July 22, 2013 - 11:57 AM

#7

Glad you found the problem.


Thank you.

  • gcally

Posted July 23, 2013 - 02:37 AM

#8

So what ended up being your final configuration? Still running the YZ header or R&D bowl?

Are you going to try and add some of the stuff back to the bike now that you found the original gremlin?

  • Krannie McKranface

Posted July 23, 2013 - 08:32 AM

#9

Yz header: yes
R&D powerbowl 2: no
Putting any pieces back on: yes: PB 2

  • kawi380

Posted July 25, 2013 - 09:31 AM

#10

So what does the stock 08wr450 needle jet supposed to look like? The one with 16 holes or the one with no holes? I'd have to remove one to see what they look like.

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  • Krannie McKranface

Posted July 25, 2013 - 02:56 PM

#11

So what does the stock 08wr450 needle jet supposed to look like? The one with 16 holes or the one with no holes? I'd have to remove one to see what they look like.


It's supposed to be a 16 hole version, but many many were shipped with the "no holes" version.
My 2003, 2006 both had 16 holes. My 2007 did not, and my 2008, who knows....

  • kawi380

Posted July 25, 2013 - 03:33 PM

#12

It's supposed to be a 16 hole version, but many many were shipped with the "no holes" version.
My 2003, 2006 both had 16 holes. My 2007 did not, and my 2008, who knows....


Great, now I am going to have to pull it out and check just to make sure. :banghead: even though it seems to run good.

  • Krannie McKranface

Posted July 25, 2013 - 04:55 PM

#13

Great, now I am going to have to pull it out and check just to make sure. :banghead: even though it seems to run good.


If it ain't broke......tear it down to the last bolt anyway and modify everything, and get it running really really good, then do it again a few more times, until you reach Nirvana......or don't fix it.

  • kawi380

Posted July 25, 2013 - 07:36 PM

#14

If it ain't broke......tear it down to the last bolt anyway and modify everything, and get it running really really good, then do it again a few more times, until you reach Nirvana......or don't fix it.


My winter jet is coming up next. Will check then, if I can wait that long. Now I am curious.


Yep, gonna pull it tomorrow.

  • gcally

Posted July 26, 2013 - 03:53 AM

#15

I think the 2007-2011 do not have any holes.

So far I have had a 07, 09, and 11 WR450 carb apart in the last couple of months and none of the needle jet tubes had any holes in them.

Picture is from a brand new 2011 WR450 carb.

Attached Thumbnails

  • IMG_10201.JPG

Edited by gcally, July 26, 2013 - 03:54 AM.


  • stevethe

Posted July 26, 2013 - 05:31 AM

#16

I think the 2007-2011 do not have any holes.

So far I have had a 07, 09, and 11 WR450 carb apart in the last couple of months and none of the needle jet tubes had any holes in them.

Picture is from a brand new 2011 WR450 carb.


Correct, I have a 07,08,and 09 no holes. The holes wouldn't make any difference anyways. The carb main air jet area is not drilled through, so it wouldn't do anything to have the holes.

  • Krannie McKranface

Posted July 26, 2013 - 05:33 AM

#17

I think the 2007-2011 do not have any holes.

So far I have had a 07, 09, and 11 WR450 carb apart in the last couple of months and none of the needle jet tubes had any holes in them.

Picture is from a brand new 2011 WR450 carb.


I just went through the parts fiche: 2000-2003 WR's all have the 5JG 14264 Needle Jet, and the later years have the 5TJ14947 Jet.
I assuming that's the 16 hole vs the no-hole versions.

  • kawi380

Posted July 26, 2013 - 05:39 AM

#18

I think the 2007-2011 do not have any holes.

So far I have had a 07, 09, and 11 WR450 carb apart in the last couple of months and none of the needle jet tubes had any holes in them.

Picture is from a brand new 2011 WR450 carb.

Correct, I have a 07,08,and 09 no holes. The holes wouldn't make any difference anyways. The carb main air jet area is not drilled through, so it wouldn't do anything to have the holes.

I just went through the parts fiche: 2000-2003 WR's all have the 5JG 14264 Needle Jet, and the later years have the 5TJ14947 Jet.
I assuming that's the 16 hole vs the no-hole versions.


Good. Now I can just go ride and not worry that my bike could run just a tiny bit better. :ride:

  • KennyMc

Posted July 26, 2013 - 07:31 AM

#19

Did you change the needle jet and the RD Powerbowl at the same time?

  • stevethe

Posted July 26, 2013 - 05:23 PM

#20

Good. Now I can just go ride and not worry that my bike could run just a tiny bit better. :ride:


Oh no you don't get out of this that easy. You could always drill the hole or have it drilled through. :rolleyes:





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