Big pilot jet 08 wr450f


6 replies to this topic
  • wanawakeboard

Posted October 29, 2010 - 11:41 PM

#1

Folks I have a question, I have an 08 wr450 and have a white brothers xcr pipe, air box mod grey wire removed, and throttle stop cut, stock otherwise.
When I bought the pipe the directions said no jetting changes required, however I noticed after the install she was a little harder to start, but ran great after warm up and had no problems. Everything I have read on jetting calls for 45 or 48 pilot and 168 or 170 main or maybe a 172 main, so I thought I was running lean, however according to rocky mountain my stock pilot is 70 and my main is 150, so if the pilot is responsible for off idle to say half throttle and I have this seemingly huge pilot jet how can I be lean? all the jet kits Ive seen have the afore mentioned 46-48 pilot and a big main what gives? should I jet the thing? I dont want it to overheat because its rich OR lean? Im confused? any help?:excuseme:

  • CanadianWR450

Posted October 30, 2010 - 02:22 AM

#2

I believe your stock pilot is a 45 in the US, and a 48 outside of the US.

Depending on where you are and altitude stock jetting will be lean from the factory, and even more so just with the free mods. Adding the pipe made it even leaner.

So, to answer your question: Yes, you probably need to rejet, and your probably lean (depending on altitude, etc..)

This is the most comprehensive jetting chart on here I have seen for the WR450 from Indy450, but take note that it is referring to JD needles, not OEM needles.
You can always simply buy a JD Jetting kit as well. Follow JD's instructions to the letter, and it takes all the guess work out.

re-jet the bike using INDY450's jetting chart:
Elevation 0 to 4,000. feet

30 to 45 degrees: 172 main, JD Blue #5, 48 Pilot, 2.0 turns, 75 starter jet, #0 leak jet
45 to 60 degrees: 170 main, JD Blue #4, 48 Pilot, 1.75 turns, 72 starter jet, #0 leak jet
60 to 75 degrees: 168 main, JD Blue #3 or JD Red #5, 48 Pilot, 1.5 turns, 70 starter jet, #40 leak jet
75 to 90 degrees: 165 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #50 leak jet
90 degrees plus: 160 main, JD Red #4, 45 Pilot, 2.0 turns, 65 starter jet, #60 leak jet

Elevation 4,000 to 8,000 feet:

30 to 45 degrees: 170 main, JD Blue #4, 48 Pilot, 1.75 turns, 72 starter jet, #0 leak jet
45 to 60 degrees: 168 main, JD Blue #3, 48 Pilot, 1.5 turns, 70 starter jet, #40 leak jet
60 to 75 degrees: 165 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #40 leak jet
75 to 90 degrees: 165 main, JD Red #5, 45 Pilot, 2.0 turns, 65 starter jet, #50 leak jet
90 degrees plus: 160 main, JD Red #4, 45 Pilot, 1.75 turns, 65 starter jet, #60 leak jet


Elevation 8,000 to 11,000 feet: ( Note you will loose a lot of power due to altitude but your bike will idle and not foul plugs!)

45 to 60 degrees: 165 main, JD Red #5, 48 Pilot, 1.25 turns, 70 starter jet, #40 leak jet
60 to 75 degrees: 160 main, JD Red #4 , 45 Pilot, 1.75 turns, 68 starter jet, #50 leak jet
75 to 90 degrees: 158 main, JD Red #3, 45 Pilot, 1.5 turns, 65 starter jet, #60 leak jet


and refer to my tutorial when jetting:
http://www.thumperta....d.php?t=309069

  • wanawakeboard

Posted October 30, 2010 - 06:49 AM

#3

Thanks for the reply, however Im pretty sure my pilot jet is already a 70. I looked up the specs on my bike at Rockymountainmc.com Not saying they are absolutely correct but they have always been correct so far. I guess the first step is to confirm the pilot jet size from the factory, why would the factory use such a big pilot?

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  • CanadianWR450

Posted October 30, 2010 - 07:07 AM

#4

Well, mine is a 04, and I have the full factory manual.
As per the manual, my bike is a 48 pilot (Canada), and I have been in my carb, and can confirm it is a 48.
The manual states for US bikes, it's a 45.

Unless there is some DRASTIC changes between the 04, and 08 bikes, I believe rocky mountain may be experiencing technical difficulties.

That also explains why pretty much EVERY jetting set up you can find on here in the jetting database states a 45, or 48 pilot.

I'm 99.999% positive your bike did not come with a 70 pilot jet from the factory.

  • wanawakeboard

Posted October 30, 2010 - 08:11 AM

#5

Thanks! I appreciate the input, I have the manual here somewhere.. update ...ok according to the book, I have a 162 main, I have a 70 pilot air jet (not sure about what this is) and I have a 45 pilot jet at least I figured out the confusion, with that said and my hard start condition does everyone still think I need to re-jet? or might I just be able to do some fuel/air screw adjustments? I know there are tons of jetting answers on here so many in fact it gets confusing, I ride everywhere from 1000 to 6000 feet generally and have the snorkel removed xcr white brothers pipe, throttle stop removed and grey wire disconnected... I wish it was just as simple as (pick this combination) just looking for opinions because like most others I want to do it just once... Im not a racer just a woods rider this jetting will be more for making my bike run cool and last rather than performance (I do ride hard occasionaly) but for the most part my idea of a good time is a trail ride followed by a BBQ and a few beers... thanks everyone!

  • wanawakeboard

Posted October 30, 2010 - 08:12 AM

#6

seems you were right canadian! however your tutorial link isnt working... thank you very much for the info... I was thinking of just taking it to the shop to have them do the jetting but I wanted to know what jets I wanted and what I was talking about when I went down there, I look at that carb all hidden in there and think hell no... is it tough to do yourself?

  • CanadianWR450

Posted October 30, 2010 - 08:35 AM

#7

I recommend getting the JD Jetting Kit, and installing it yourself. Simply follow the direction on what jets and needle to use for your conditions and follow them to the letter. Do NOT second guess JD's recommendations, the cost of the kit is IN those recommendations, and the R&D for those recommendations, not in the hardware in the kit.
This takes all the guess work out, and it is done the first time right if you follow his instructions (unless you have a heavily modified bike, which you do not.)

Can you get it just as good as the JD kit yourself?
Yes.

Can you get it just as good, in one shot, without trial and error, and needing to get at the carb multiple times to get it right (NOT fun on a aluminium frame bike)?
NO (My opinion).

You getting into the carb, and installing the kit will be very rewarding for you, and everyone should know the basics of their bike in my opinion.

You should also get a adjustable fuel screw, and install it at the same time if you do not have one already. I consider a adjustable fuel screw pretty much mandatory.

PS : With stock jetting, and the free mods/pipe that you have done, yes, I think you would be a little lean, and should re-jet, especially if you noticed the difference as soon as you installed the pipe. The free mods alone may not have been enough to re-jet, and the pipe alone may not have been either (as per the pipe instructions), but both together is another story.

The fuel screw alone may be enough to solve your starting issues for that matter. But, if your going to go through all the work to install the fuel screw, if the $$ for the JD kit ($70-ish??) isn't a issue for you, I would do it all at once, and be done with it.




 
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