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jjj109

2003 wr450f jetting problem

16 posts in this topic

Hi guys,

I went thru the jetting datebase and looked at what everyone is running in the 03's. This is were my jetting is at now. main 150, pilot 52, needle stock on 5th clip down, check tps it is within the ranges. Fuel screw 3 turns out

mods on bike:

yosh trc comp slip on with 96db SA in it

grey wire trick

air box lid off and snorkel off bike,

yz exhaust cam,

55 degrees out when jetting

I started out with a 162 main, 50 pilot, 4th clip down on needle. oh yea AP pump is adjusted just like in the manual with no play at the lever. Bike was running way rich. dropped the main jet to 158, still rich, went down to a 150 main, plug looks a little white. still had the nasty bog:banghead: went up on the pilot 52, and dropped the needle to 5th clip. it seems better still bogs a little bit. the whole time I adjusted the fuel screw to see how it effected the bike. it seems like i need the next pilot up . in the jetting data base everyone is running a 48 or 50 pilot. any suggestions ?

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If you are using your plug reading to determine jetting, don't bother. It isn't accurate on a four stroke, unless you are using race gas and a fresh plug every time, and use the 'engine cut' method. When I use Shell gas from my local pump, it makes the plug black. Chevron makes it grey. Same jetting.

You need to create a 'lean bog' condition with your leak jet before deciding on a main jet size. An overly rich AP setting (which is stock) will make main jet sizing confusing. Once you do this you can pick the right size without getting the APump dumping gas and confusing the issue. I don't think your are large enough on the main. I have a 168 on my '03 with the stock pipe (and gyttip) and cam. All other mods performed.

I got lazy and bought an R&D power pump and bowl, and it works amazing. Adjusted my leak jet in 10 minutes, and I cannot get it to bog, and have much much better throttle response.

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oh I for got to add that I have the boysen quick shot on the bike also. sorry guys:bonk:

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it sounds like your main jet is too small. my '05 is running a 168 main and a 48 pilot, but i put in a 40 leak jet that solved my bog.

it doesn't work for everyone, but it helped me quite a bit.

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my buddy has a 2006 yz450f. he tried switching the leak jet 2 different times going in both directions a smaller one and a larger one. he said he didnt notice not a bit of difference when switching the leak jet and that was the only jet he changed. it still has a very small bog :p

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I have a 04

170 Main

48 Pilot

2 5/8 Turns out

Plugged leak Jet

Needle Clip I think is 3rd down from the top

Runs well, a little bog but not while riding, idle is set low on mine also not at the factory 1800 RPM

Your carbs need adjusted from what you posted.

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What does a plugged leak jet mean? Did you put in a leak jet with no hole or something? How does that work. I happen to be the guy he is talking about with the 2006. I put in a very small number leak jet to stop up the leak and spit more fuel. Your jetting is about what I richened my bike up to. 5th or 6th needle clip, not fourth, that is too lean.

I hope is bike is just running lean and he needs to richen it up. the plugged leak jet sounds like a good idea. my bike will bog if you rev it too fast at idle and even cut out, but it is better than it was when I got it new with the stock jetting. The thing totally rips on the track, not bog at all.

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What does a plugged leak jet mean?

I tried the smallest leak jet I could find, #35 and still had a bad bog so I soldiered my original leak jet closed with silver soldier, much better!

My needle is at the Stock Setting clip wise from what I remember, I have it written down in a file and that could be 4th from the top.

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cool. that sounds good. The 5th needle clip is good for me out here.

You better throw on that 2006 carb on Rob's bike ! Gonna get that wr450f giong.:ride: Just collecting dust in my shed:bonk:

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.....pilot 52, .....it seems like i need the next pilot up . in the jetting data base everyone is running a 48 or 50 pilot. any suggestions ?
A 52 pilot is huge. I use either a 45 or a 48.

Have you ever had the slide out of the carb? The last time I heard of someone using a 52 pilot, their slide was up-side-down.

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A 52 pilot is huge. I use either a 45 or a 48.

Have you ever had the slide out of the carb? The last time I heard of someone using a 52 pilot, their slide was up-side-down.

Yeah i know 52 is big but the bike has extensive mods done to it. How much is your bike modded ? I have yet to start working on this bike . Just dont have the time or space to work on it. Hopefully we will stop getting snow and I can get it finished up !:thumbsup: This has been crazy year for snow man. Four snow storms in February and one in December Im over it

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