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08 WR450 Winter Jetting

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One of my first real post here at Thumper and I hope to be able to contribute to the forum here in the near future (once I up my bike knowledge). Great information here and I've already had several questions answered in the hunt for my main problem.

I purchased my 08 WR450 this fall from a good friend (who took really good care of it) with the intention of mating this bike with a Timbersled Mountain Horse snowbike kit. So far the installation and first ventures out in the snow have been great and I can't wait to really tear it up.

With that being said my main problem is my jetting. Currently the bike is setup for around 3,000ft and 65F. I've gone through the entire jetting database and I can't find anyone with my specific requirements. 6,000ft at 20F with medium to low humidity would be a pretty accurate description of where 80% of our riding takes place.

I would be grateful if anyone could help steer me in the right direction. My local dealership keeps telling me to check my manual. I have a manual and the chart isn't in there from what I can see.

Thanks folks!

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One of my first real post here at Thumper and I hope to be able to contribute to the forum here in the near future (once I up my bike knowledge). Great information here and I've already had several questions answered in the hunt for my main problem.

I purchased my 08 WR450 this fall from a good friend (who took really good care of it) with the intention of mating this bike with a Timbersled Mountain Horse snowbike kit. So far the installation and first ventures out in the snow have been great and I can't wait to really tear it up.

With that being said my main problem is my jetting. Currently the bike is setup for around 3,000ft and 65F. I've gone through the entire jetting database and I can't find anyone with my specific requirements. 6,000ft at 20F with medium to low humidity would be a pretty accurate description of where 80% of our riding takes place.

I would be grateful if anyone could help steer me in the right direction. My local dealership keeps telling me to check my manual. I have a manual and the chart isn't in there from what I can see.

Thanks folks!

What jetting do you have now?

Your 3,000 spec is not far enough from 6,000 to need anything more than a tweek of your fuel screw, and maybe a leaner needle or needle setting.

I ride my '07 WR450 from 0-7,500 ft with no jetting changes

Main= 165

Pilot= 45

Fuel Screw= R&D extended with 1.25-1.75 turns

Needle = NCVS 3rd

Leak = 50

Air = 100 (stock)

Power = 50 (stock)

Apump detent spring = merge racing upgrade

Apump linkage setting = 1.5 cw from stock (just missing the slide)

Slide plate = stock with fresh vacuum seal gasket

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Sorry for the long reply. Was away the last two days.

I called up the previous owner (a good friend) and he could not elaborate on the current settings in regards to jetting. He directed me to call the local dealership (Penco Power Products in Kalispell, MT) and have them search through the records for the settings. Penco's story was that the bike work was done pre-sale and there are no specific records except:

Year: 2008

Model (400 - 426 - 450): 450

Cam Timing (WR/YZ):

Main jet:

Pilot Jet: #45

PAJ:

Leak Jet: #40

Starter Jet:

Fuel screw (turns out):

Needle Model/Clip position:

Grey Wire Mod (Y/N): Y

TPS Connected (Y/N):

Airbox Snorkel/Lid (on or off):

AIS Removed (Y/N): Y

Airfilter Brand:

Exhaust Brand: FMF Q4 (not full exhaust)

Average Altitude: 6000 ft

Average Temperature: 20F

Average Humidity: 40%

Degree of Satisfaction (0-10):

Additional Mods/Comments:

I know, there are a lot of blanks there and I really hammered the guy to provide me with more information. The bike was dyno'd but the settings weren't recorded. He likened the situation to KFC: they have a secret recipe for the making the bike run great and they don't just give out the information. SUPER HELPFUL, right?

Anyways, what more would you need me to do to better help me? I don't know how to tear down the carb but I bet I know a couple people who do. All I was told was the bike was dyno'd, got the GYTR AIS kit, grey wire cut, and a FMF Q4 exhaust.

Wish I had more for you :bonk:

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Just had the tech at Penco call me back. He was unable to find the specific settings on my bike, but he pulled up information on other 08's that Penco modified and these are the general house settings. Note: the ? before each answer indicates the typical house settings and these are the assumed settings on the bike now. I know, ASSUMED, but it's the best I can do.

Year: 2008

Model (400 - 426 - 450): 450

Cam Timing (WR/YZ): WR

Main jet: ?150

Pilot Jet: ?50

PAJ: ?Factory 70

Leak Jet: #40

Starter Jet: ?Factory 65

Fuel screw (turns out): ?1 1/2 - 2 (normally)

Needle Model/Clip position: ?#2

Grey Wire Mod (Y/N): Y

TPS Connected (Y/N): Y

Airbox Snorkel/Lid (on or off): off

AIS Removed (Y/N): Y

Airfilter Brand: Factory

Exhaust Brand: FMF Q4 (not full exhaust)

Average Altitude: 6000 ft

Average Temperature: 20F

Average Humidity: 40%

Degree of Satisfaction (0-10):

Additional Mods/Comments:

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That 150 main jet is pretty lean.

At 3,000 feet and cold temps, a 162 is pretty safe. A 160 during the summer will work.

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Tiny main, huge pilot and only if they changed the needle could they have changed the clip. You need to tear her apart to see whats in there. What are your syptoms?

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Problems include:

  • hard to start at 6k when warm, lots of throttle blipping and it takes 5-6 seconds instead of 1 second
  • doggy throttle response
  • lots of backfiring and popping running down the road
  • generally seems less powerful

Granted, it's running a Mountain Horse and that saps away power, but this just seems to all be in the wrist. It was also hiccuping going down the road late day and my friend seemed to think I was getting water in my airbox (powder snow). I'm going to mod my pre-filter that goes over my stock air filter to make sure no more powder gets in there.

thanksgivingandfirstride038.jpg

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Your symptoms match the current jetting.

A 50 pilot is pretty rich, and that would seem to explain the hard start warm. However, a local dealer in Denver at high altitude puts 50's in those, and has verified correct A/f ratio with the dyno sniffer.

I would try a 48 pilot at 1.75 turns out on the fuel screw, and a 162 main when riding in cold temps.

If you leave the 50 pilot in, turn the fuel screw in to 1.5 turns out and see if it is any better.

William is the expert on these, maybe he'll chime in.

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After making a visit to the Density Altitude Calculator we were able to determine that my needs at 20F and 6500ft are the same needs of a person riding at 3,000ft in 75F weather. So, after perusing the WR450 jetting database again we were able to find an entry that came very close to those needs:

===============

Year: 07

Model (400 - 426 - 450): 450

Cam Timing (WR/YZ): WR

Main jet: 168

Pilot Jet: 48

PAJ: 110

Leak Jet: 45

Starter Jet:

Fuel screw (turns out): 1.5

Needle Model/Clip position: red/4

Grey Wire Mod (Y/N): y

TPS Connected (Y/N): y

Airbox Snorkel/Lid (on or off): off

AIS Removed (Y/N): y

Airfilter Brand: uni

Exhaust Brand: gytr 96db performance insert, p/n gyt-5tj93-75-01:

Average Altitude: 2-4000'

Average Temperature: 80

Average Humidity: low

Degree of Satisfaction (0-10): 9.5

Additional Mods/Comments: first I installed Yamaha AIS kit and found it to be a little rich for me. Bought the JD kit and installed per instructions, thick oring mod. very happy with this setup. left the gytr main air jet and leak jet installed.

===============

These figures seem to closely resemble the advice given here. What do you all think? What JD Jet Kit would this be?

Thanks again for the help!

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After making a visit to the Density Altitude Calculator we were able to determine that my needs at 20F and 6500ft are the same needs of a person riding at 3,000ft in 75F weather. So, after perusing the WR450 jetting database again we were able to find an entry that came very close to those needs:

===============

Year: 07

Model (400 - 426 - 450): 450

Cam Timing (WR/YZ): WR

Main jet: 168

Pilot Jet: 48

PAJ: 110

Leak Jet: 45

Starter Jet:

Fuel screw (turns out): 1.5

Needle Model/Clip position: red/4

Grey Wire Mod (Y/N): y

TPS Connected (Y/N): y

Airbox Snorkel/Lid (on or off): off

AIS Removed (Y/N): y

Airfilter Brand: uni

Exhaust Brand: gytr 96db performance insert, p/n gyt-5tj93-75-01:

Average Altitude: 2-4000'

Average Temperature: 80

Average Humidity: low

Degree of Satisfaction (0-10): 9.5

Additional Mods/Comments: first I installed Yamaha AIS kit and found it to be a little rich for me. Bought the JD kit and installed per instructions, thick oring mod. very happy with this setup. left the gytr main air jet and leak jet installed.

===============

These figures seem to closely resemble the advice given here. What do you all think? What JD Jet Kit would this be?

Thanks again for the help!

I would probably go a bigger main as thats what you will be on all the time with a large load with the track. See what needles in there, you may not need a JD kit.

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