WR450F Jetting Questions

What a great site - very infomative (And entertaining at times). Thank you everyone for all the great posts. :naughty: I picked up a 2005 WR450F last week. I've done all the free mods, and all I have left is the jetting. I have the JD jet kit and the zip-ty fuel screw. I've never done jetting before, and have a couple of questions. Most of my riding will be 1000 feet or less, and 75-90+ degrees (Typical MD) - so I wanted to start out with Indy's recommendation in the jetting d-base:

165 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #50 leak jet

Questions/observations (Correct me if i'm wrong):

-The 165 main jet I believe is included in the JD kit, as well as the red needle.

-I assume the 1.25 turns is for the fuel scew.

-The stock pilot jet (Yamaha calls this the slow jet?) I believe is a 45, but the diagram gives a part number for the 48 [4MX-14948-06-00].

-The stock leak jet I believe is #50, so I should be ok there.

-Trying to figure out the 68 starter jet though. Can someone point this out on the diagram? (Hopefully this link works). Not sure what Yamaha calls this.


Thanks to all! :naughty:

I Think It Is #21 On Your Diagram.

I'm just south of you and ride from 1000' to 4500'. IMO I'd send the JD kit back and pick up an '04 WR needle. I'm running a 168 main, 04 needle #4, 48 pilot, 1.5-1.75 turns, 68 starter, stock leak jet. The bike runs crisp and strong, no bog at all, and starts as soon as I hit the button. I'm not knocking the JD kit, I just don't see the need when the 04 needle works perfectly.

OK, thanks. I think you're right. I see that a #68 starter jet is available under the YZ parts list. It only listed a #65 under the WR parts list and was throwing me off.

What is the starter jet doing? Does it only affect starting? Mine starts very easy, so should I just leave it alone for now? :naughty:

Just jetted it. Completely eliminated the backfiring, and response is good. I didn't change the starter jet, and it still starts fine (Unless I am missing something). Thanks to all for your help. :naughty:

If your bike starts fine leave the starter jet alone.

Did you try the blue needle? The red needle is for 6000 feet.

My JD kit reccomends the 168 main jet.

Did you open up the throttle side air box?

My WR with a White Brothers pipe is really fast. For once I'm just going to leave the thing alone and ride.

I have a question as well. I have the JD kit and Zip Ty screw. Air box is completely open. All free mods are done and I'm running a FMF Power Core.

I installed the 170 main jet, the red needle ( I think..it's been awhile) in the recommended clip position. I have the mixture screw out 1.5 turns. Stock pilot jet.

So here is the problem. The exhaust indicates a rich condition. Bike runs great, starts easy. But the screen in the pipe is black and when you rev the bike is let's out a little puff of black smoke. I've jetted many a Harley and after getting her dialed in the exhaust residue would be gray. Seems slightly rich becuase of the black sooty residue and puffs, but not exceedingly so. I live and ride primarily at about 100 feet above sea level.

Any thoughts? Should I go to the 168 main? Should I try to dial it out with the mixture screw? It's not serious, just a refinement issue. I know it's a little lean on the bottom because if you snap the throttle it will hesitate and sometimes flame out. But I know how to fix that.

Anyone have any opinions? I want to ride and so spend as little time as possible dicking around with the carb if someone has experienced this.



The JD kit instructions say to use the blue needle for low altitude.

The black smoke is the accelerator pump I think.

I have a 168 in my 05 450.

Most 4 strokes I have seen have black soot inside the pipe.

You can shut the motor off on any 4 stroke by hitting the kill switch or snapping the throttle open.

Did you try the blue needle? The red needle is for 6000 feet.

Well, I was torn weather to try the blue first or just go straight to red. The red is supposed to also be for hot an humid, and most of my riding will be in 75-95 degrees and humid.

In the case mentioned then I would have used the blue needle. I am certain I used the low altitude, warm weather needle even though the weather was cooler at the time.

Once again, it runs pretty darned good, and starts pretty easy. It is just that the tail pipe and little puff of smoke indicate a slightly rich condition.

Does everyone experience this? If so I will worry no more. This is my first 4 stroke dirt bike in 20 years so I am refining my knowledge. As I said on my Harley once she was dialed in the tail pipe had a light gray residue and no smoke when popping the throttle.

Any experience with this would help me ascertain if it is right or not. I know to eliminate the flame out when snapping the throttle I'm going to have to richen the pilot and leak jet, but it may be that I'm running rich through the middle and top to boot.

Any suggestions?


You can shut the motor off on any 4 stroke by hitting the kill switch or snapping the throttle open.

I've jetted my bike, opened the airbox, cliped the grey wire, zip-ty fuel screw (2 turns out), and AIS removal. I'm at 800ft ASL, and used the blue needle at #3 and the 170 main. (better rich than lean right?)..

Either way, the bike runs great, starts easy, except if I snap the throttle fast from idle, it'll bog. A mild snap (one that would actually be controllable if I were riding the bike) behaves fine. But if I hit it really quick, it'll die.

You're telling me that is normal? I'm not being sarcastic, I've got little jetting experience. I'm just wondering. I've got no complaints, other than that.

Also, if I do kill it, and the bike is really warm, it typically won't start unless I twist the throttle once, open the hot-start, and then start the bike. If I neglect to twist the throttle, it will just crank away, and never start up. Is this something the boyseen accel pump thingy would fix, or is this something else?



Minion, put in a 72 starter jet, 48 pilot and a 40 leak jet and say good bye to the lean bog off of idle. :naughty:

Minion, put in a 72 starter jet, 48 pilot and a 40 leak jet and say good bye to the lean bog off of idle. :D


I made some changes per your recommendations to try and fix my lean bog. I probably changed too many things at once, (I hate taking apart most of my bike to reject), so I'll probably be kicking myself once you reply. =)

Either way, here is a list of the mods I have performed, and my previous jet settings:

170 main, blue needle #3, all other jets stock ( '05 WR450 )

throttle stop mod

open air box

disconnect grey wire

AIS removal

stock muffler

I pulled my plug today, and the tip of the cathode was tan, but everything else was sooty (as well as the tail pipe). So, I'm thinking I may have had it a bit rich. It was jetted a lot richer than your recommendations on the sticky jetting post.

Either way, I pulled the carb, replaced the needle with the JD Red #5, replaced the 170 with a 168, replaced the stock starter with a 72, stock pilot for a 48, and stock leak for a 40.

I put everything back together. It started up real easy, but the lean bog was still there.

I know you said on the sticky to use a 165, but that shouldn't matter for idle to 1/4 throttle, right? I wanted to be a little rich in that area of the carb than lean - I'd rather clean spark plugs than replace pistons. Sure would be nice to have fuel injection and a mass air flow sensor right about now. :)

Do you have any suggestions? I'm at about 800 ft ASL. Today was a little cool out - about 63 when I did my ride test. It still runs a hell of a lot better than stock (boy did that suck), but it bothers me that the lean bog is still there - that really affects tight single track.



I hate to say it but if you have the jetting set up the way you described then your AC pump squirt timing and direction of squirt are not right!

Go to this web site and read up on tuning the AC pump circuit:


That is where the solution for the set up is. :)

Hey, can someone please help. Refering to the diagram above, I know 19 is the main jet, 20 is the pilot jet (aka slow jet, per Yamaha), and 21 is the starter jet (aka jet, per Yamaha). What are 22 (jet, main #85, per Yamaha) and 23 (jet #70, per Yamaha). With the help of this forum I should be able to sort out the rest of my jetting issues. Everyone's help is amazing and appreciated by all of us beginners.


03 WR450f

92 WXE360

86 CR250

OK, I think I've got it. :) Though my eyes are burning after almost 2000 WR threads. :)

On the diagram above:

19 - Main Jet - 3/4 to full throttle

20 - Pilot Jet (aka slow jet) - 0 to 1/4 throttle

21 - Starter Jet - Choke circuit

22 - Pilot Air Jet - Vacuum at pilot jet (smaller jet = higher vacuum)

23 - Leak Jet - Accelerator pump circuit (smaller = more squirt)

Someone please correct me if I'm wrong.

'03 WR450f

'92 WXE360

'86 CR250

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