45 vs 48 Pilot Jet

Greetings,

I've a stock WR450 with the basic mod's. I spoke with JD Jetting directly when I purchased their kit and they were pretty insistent about using the stock 45 pilot jet with their kit - for my environment.

0-1000 feet 60-85 degree's

I've recently added a YZ muffler and now I'm wondering about that 45 pilot jet again. It seems from all of my searches that the most common usage after modifying stock WR 450's is to go to the 48 pilot for my environment.

I understand that only experimenting will tell for sure but my bike does seems to run great with the 45 I'm only a bit concerned about running lean while on the pilot circuit.

Thought?

Thanks!

A slightly lean pilot isn't going to harm anything. If it starts and idles good, then i would leave it in there. Do you have an adjustable fuel screw? You can use an adjustable fuel screw to compensate for slightly lean or rich pilot jet.

p.s. i'm jealous of your weather. it's triple digits here.

Here's the question I put on the jetting forum:

"Can anyone give me a recommened starting point for a '04 WR450F stock except doing the cutouts on the airbox (with a Twin Air filter) and a GYT-R Performance Insert installed. I'm near sea level."

Here's Eddie's (the jetting Guru) answer:

get your self a JD jetting kit or

160 main jet

EMP needle

clip 3

45 pilot jet.

:ride:

Thanks Guys,

Thumper_Bloke - Yes, I do have an adjustable screw and you are correct - even a 1/4 turn makes a big difference.

BTW - you should be jealous. I left Shasta County, N. Calif. because I couldn't stand it when we had 30+ days over 105 degrees. I kept seeing Seattle at 75 degree and decided that's where I was going. Worked out well for me.

:ride:

...if the experts suggest a 45 pilot at sea level I'm not going to argue!

Here's Eddie's (the jetting Guru) answer:

get your self a JD jetting kit or

160 main jet

EMP needle

clip 3

45 pilot jet.

:ride:

A 160 Main and 45 Pilot at/near sea level? That's gotta be a mistake. The bike comes richer on the main from the factory and it's considered lean at that. If you want some real world, WR-specific jetting specs, then go to the sticky database and look at Indy's chart. It was created specifically for the '03-'04 WR with an aftermarket exhaust and free-modded airbox. I know from personal experience that Indy's chart is the definitive reference for those model years. From my own work on my '05, I found a couple little tweaks on the Indy chart were necessary, but it was still pretty damn close...SC

Wow another 05 jetting disaster. My JD needle and jet settings must be way off if at sea level you can run leaner than my bike does at 3200ft. I would bet that it runs hot and is hard to start and has no top end. Heat kills the intake valves so don't run lean. Just for you JD guys his chart for the 05 says 48 pilot 170 main, blue needle in 5th. So the red needle in the 3rd and 168 main with 48 pilot is what worked. Good luck!

Wow another 05 jetting disaster. My JD needle and jet settings must be way off if at sea level you can run leaner than my bike does at 3200ft. I would bet that it runs hot and is hard to start and has no top end. Heat kills the intake valves so don't run lean. Just for you JD guys his chart for the 05 says 48 pilot 170 main, blue needle in 5th. So the red needle in the 3rd and 168 main with 48 pilot is what worked. Good luck!

That is what I would have suggested and if it stumbles a little off idle (1/8 to 1/4) throttle then raise the clip to RED 4.

Additionally try starting with the tables as recommended by Indy and Clark4131, they are very close to ideal, perhaps slightly rich for where I live but we are over 80% humidity every day of the year - should be OK for you.

I second the "dont run lean"....

FYI Recent article in UK BIKE Mag demonstrated more power (3%) and better operation away from the "ideal" 14.7 air fuel ratio. Bikes run BEST around 12.8! Thats 10% difference (richer) from theoretical ideal! :ride:

:ride:

To quote Eddie from the jetting sticky posts:

how to confirm your pilot circuit setting

seems like the most common jetting issue that comes up are pilot circuit related.the following is a sure method to choose the needed changes.

with the bike warm and idleing turn the fuel screw in till the idle drops/misses.then go back out till the idle peaks/smooths.

this should happen between 1 and 2.5 turns on a fcr carb and 1 and 3 turns on a cv.

if you end up at less than 1 turn you need a smaller pilot jet.more than 2.5 (or 3 turns on a cv) you need a bigger pilot jet.

choose the appropriate size and retest.

__________________

Now this makes sense!

A 160 Main and 45 Pilot at/near sea level? That's gotta be a mistake. The bike comes richer on the main from the factory and it's considered lean at that. If you want some real world, WR-specific jetting specs, then go to the sticky database and look at Indy's chart. It was created specifically for the '03-'04 WR with an aftermarket exhaust and free-modded airbox. I know from personal experience that Indy's chart is the definitive reference for those model years. From my own work on my '05, I found a couple little tweaks on the Indy chart were necessary, but it was still pretty damn close...SC

no mistake.

the needle end demension dictates the main jet selection.the stock WR needle has a bigger end demension than a E taper needle.

E taper needles use smaller main jets.

no mistake.

the needle end demension dictates the main jet selection.the stock WR needle has a bigger end demension than a E taper needle.

E taper needles use smaller main jets.

Ah,so. I see what you're talking about. The sticky chart specs apply to the use of the JD kit and its particular needles. The alphabetic designations for the various needles are a bit confusing. I prefer Red for hot weather, Blue for cold :ride: ...SC

Greetings,

I've a stock WR450 with the basic mod's. I spoke with JD Jetting directly when I purchased their kit and they were pretty insistent about using the stock 45 pilot jet with their kit - for my environment.

0-1000 feet 60-85 degree's

I've recently added a YZ muffler and now I'm wondering about that 45 pilot jet again. It seems from all of my searches that the most common usage after modifying stock WR 450's is to go to the 48 pilot for my environment.

I understand that only experimenting will tell for sure but my bike does seems to run great with the 45 I'm only a bit concerned about running lean while on the pilot circuit.

Thought?

Thanks!

I went from the 48PJ to the 45PJ this summer. My bike seems to run better in the heat with the 45. I am about 2 turns out on the FS and i am running anywhere from sea level to 3000 feet right now. Hope this helps.

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