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ill_caper

For Jetting Gurus

12 posts in this topic

I am a little confused, hopefully someone here can help. I have an 03 wr450f. I had the airbox snorkle removed, grey wire removed, all other free mods and a quiet is cool baffle. I jetted it with a 165mj and jd red 4th clip and it ran great. I decided to change to the YZ airbox and I definitely did not get the improvement I thought I would. It doesnt see to start as well, stalls easier and definitely lost the "hit" that it used to have. It seems to have basically lost power the whole range. It doesnt make sense to me. I opened up the airbox so it could breathe much better than the WR airbox. From a very wise tt member( NCmountainman), I found out that I should increase the mj =170 and the pj= 48, paj =120 and lj =40. I know that the stock YZ mj =162. From a couple excel jetting calculators I am getting that I should lean out my mj with my temp and altitue(60 - 90f + 200-1000ft). I would think that by opening up the airbox(changing to the yz airbox) I would need to richen up all of the circuits drastically? Am I wrong? Would anyne mind enlightening me? Sorry for the long message but I just want my WR to rip again. By changing all of my jets to the ones advised by sensai NCMOuntainman it almost seems like it woud richen some circuits and lean out others?Thanks in advance. -D :)

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YZ airbox + more air flow = more air to the carb = the need for more fuel. Result: you need bigger jets. NC's specs are spot on as they're increasing all the jets, except the leak jet, which works the opposite of the other jets (smaller leak jet = more fuel to the AP squirt). Whatever calculator you're using is goofacha! :) ...SC

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Here's the jetting chart from Jetting Guru Indy...

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

Remember Grasshopper, when you can snatch the leak jet from my palm, it will be time for you to roost!...SC

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i'm guessing your in the 75-90 range at the moment,remember your gonna have way more top end with that airbox,so a 170 mj is needed keep the clip @4,try the 45pj if you think 48 will be too much,also try removing the baffle,the stock pipe w/out the baffle is not that loud,and it will allow the extra air to exit,otherwise its like pissin' against a wall :thumbsup:kung fu ain't my thang,its more like sensai-melia :)

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I put in the 170 mj today and it was much better. I also switched out the red needle for the blue needle 4th clip. Does that make sense. I just assumed that the blue needle was a little more rich so it may benefit me. It is so easy to change the needle that I could always go back if need be. I ordered the boyessen pump cover last night and I am going ot call sudco to order a 48pj, 120 paj and a 40 lj.This should be good right? Thanks again Dr. greenthumb :) . Im a big fan of the sensai-milia sp? as well.

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I'm kind of new to the whole rejetting thing (on bikes anyway...did many a holley) so I have a couple questions if you don't mind

Do you gurus take the carb off to rejet? Any links showing pictures the re-jetting? :)

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I always take the carb off to rejet. I usually end up doing all of the jets at once and follow my set jetting chart that works very well for my bike and mods. I rejet for each season and for high altitude trips. It is a good time to clean the carburetor with carb cleaner as well. You do not need to rejet very often if you do it right for the seasons/conditions. :)

Note: Mods play a big factor in jetting! :)

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It depends on which jets you need to change. For the main jet you can use a 17mm socket to take off the nut at tghe bottom of the carb and you can access the jet from their. For the needle you can do the same except on top of the carb. You just have to loosen up the clamps holding the carb on and rotate it enough to access the nuts. Indy knows alot more than me so his advice is definitely dead on. Him and NCmountianman KNOW the WR. I learend alot about the carbs from them.

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I have also learned alot from read Indy and NCMountainmans posts :) Did my carb two weeks ago and after doing it once, it is really quit easy :)

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I always take the carb off to rejet. I usually end up doing all of the jets at once and follow my set jetting chart that works very well for my bike and mods. I rejet for each season and for high altitude trips. It is a good time to clean the carburetor with carb cleaner as well. You do not need to rejet very often if you do it right for the seasons/conditions.

I have the factory shop manual and it lists the order to remove the carb. Is this good to use or are there some tricks?

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Take the tank off, remove the right side capacitor and carb cover.

Disconnect the throttle cables at the carb.

Unplug the TPS at the carb connector.

Loosen intake and engine boot clamps.

Rotate the carb to the left slightly and remove the hot start cable at the carb.

Take the handle end of a hammer and pry the intake boot away from the carb using the frame as a leverage spot.

Remove the carb from the engine boot and pull out the left side of the bike.

No need to remove the subframe. :)

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Thanks Indy. :) I'll be working on my 426 so no hotstart cable but I should be good to go with the rest :)

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