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Taewa

Main and pilot jetting question

6 posts in this topic

Hello thumpers... I have a '99 WR 400 that I think may need rejetting, but I am not sure what sizes to go with. I think the main is still at a 170, and pilot is stock. I have moved from Utah to Portland and now to Boise, Idaho. I have also done several mods to bike including - air box lid, gray wire, White Bros exhaust , and cut throttle stop. Right now the main symptom is the bike boggs down during the first 1/4 of giving it throttle. Occasionally it also cuts out and/or dies when I have done a hill climb and just come off the gas quickly at the top of the hill.

1) Any thoughts on what size jetting I should look at considering my mods and location (Idaho) ???

2) Any other things I should consider in regards to the dying or cutting out after major accelerations/ hill climbs?

Thanks a ton guys!

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Copied from a previous jetting question, but may solve your issues:

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.thumpertalk.com/forum/sho...d.php?t=309069

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Having dyno'd that bike at altitude, the recomendation on that chart are a little rich.

In Boise, a 158 main, a new 48 pilot at 1.75 turns out will run great.

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Good to keep in mind that the chart is for a 450, and not a 400, although I have no idea how much difference that makes........

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Great. I will try that out...maybe even get to it before winterizing the bike this year. I will report back on results. :p

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