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ohioryder

Yet another jetting problem

15 posts in this topic

First off I appoligize for this post. I have searched and read I think everything on this to the point that I am more confused and my eyes are hurting, and I am making adjustments that is creating more problems.

I have an 08 wr450f with following mods:

removed grey wire

throtle stop (from GYTR kit)

08 YZ450f exhaust

main jet--168

pilot jet--48

leak jet--45

main air jet--110 (from GYTR kit)

needle--NFLQ 4th from top

GYTR fuel screw--2 turns out (yes I checked spring, washer, and o-ring)

Here's my problem. After getting the bike back together it wouldn't start unless holding in the hot start lever. I got it started and warmed it up and took it for a ride around neighborhood roads for 10 minutes. It ran great, seemed to have alot of power, pulled very good, no hesitation, no backfire, no gurgling, it just seemed crisp. The problem was it would occationally stall half way into a turn after running it wide open. It would start up right away with the hot start and run great.

I searched the archives and found the simular situation where the person did not have the o-ring on the fuel screw. I pulled the fuel screw and the spring, washer, and o-ring where there and in that order. I reinstalled the fuel screw, and set it 2 turns out. The condition remained the same.

I then decided to try and adjust the fuel screw using the method that the user (William1) has given many times for us idots:bonk: . I started the bike having to use the choke and hot start, warmed it up, took for a 10 minute ride, then started to lower the idle slowly to its lowest point and it stalled. I then turned the idle back 1/4 turn and it wouldn't start, I turned it another 1/4 turn and it wouldn't start. I was getting upset and the battery died so I recharged the battery and called it a day.

Next day I took out the fuel screw again and double checked the spring, washer, and 0-ring, and put it back in two turns out. It started but again only with the choke and hot start lever in. Upon releasing the hot start lever the idle would drop very low but still run, but if you pushed in the choke the bike would instantly shut off. I restarted the bike with hot start lever in and choke out. Same senerio...it idles great but, when I release the hot start the idle drops very low and when I apply the hot start the idle return to normal range. So I got the bike started, released the hot start, the idle drops very low, let it warm up, but as soon as I push in the choke it still dies. I have tried to start it and turn up the idle but the idle screw does not seem to effect the idle either way. It will not increase nor decrease the idle, but it does shut off the bike at a certain point.

I am now lost! I know this is long and some of these issues have been discussed and I have tried to make the adjustments given for these senerio's but nothing is working and I am....well :ride: . Any help please...

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Did you remove the slide from the carb?

What size slow air jet is in the bike now? What was it before? What pilot jet was in it before?

Are you sure you do not have slow air and main air confused? Main air is typically a 200 and slow air is typically a 100

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No I did not remove the slide.

The stock setting was a 162 main jet, #45 pilot jet, 60 leak jet, not sure stock slow air jet (I did not remove it), and the main air jet was just a tapped whole to the right of the slow air jet.

I purchased a GYTR AIS kit which came with jets which most members on here have said is way too rich. So I went out and bought a 168 main jet, 48 pilot jet, 45 leak jet, and a NFLQ needle. The only jet I used from the GYTR kit was the 110 main air jet (I checked it again and it is listed as a 110 main air jet).

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I believe I have the slow air jet and main air jet correct. The slow air jet is on the bottom left side of the carb bell and the main air jet is to the right of the slow air jet.

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Sounds like something is clogging the Pilot jet passage.

I noticed that some others have not mentioned changing their main air jet. Do you think that by me using the main air jet from the GYTR kit that this could be the problem?

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I noticed that some others have not mentioned changing their main air jet. Do you think that by me using the main air jet from the GYTR kit that this could be the problem?
The 110 main air jet is going to richen your main jet, but your problem sounds like the pilot circuit.

Needing the hot start when the bike is cold suggests the pilot is too rich. Not running without the choke (which has it's own jet) suggests the pilot is too lean or clogged. Needing both is strange.

I'd check the pilot jet and maybe even try the 45, instead.

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I did as you did and installed all of the jets that came with the GYTR AIS removal kit but used the 168 main, 48 pilot and red JDJetting needle. My bike has run without any problems.

JDJetting talks about using their blue needle in areas that are colder/higher humidity. If you want to try the blue JDJetting needle, PM me your address and I could send it to you.

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I thought I was very careful when re-jetting and did it on a very clean table away from any dirty environment but maybe some dirt got in the pilot circuit? I think my jetting is right as it has worked for many and it shouldn't be this off to create the problem Im having. So should I remove the carb and check the jets and clean everything and try it again?

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-when I release the hot start the idle drops very low and when I apply the hot start the idle return to normal range.

-released the hot start, the idle drops very low, let it warm up, but as soon as I push in the choke it still dies.

- Removing hot start richens, needing hot start means too rich.

- Removing choke leans, running with choke means too lean

I'm stumped, but it has to be something simple.

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First, do this:

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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William1, the only way my bike runs now is with the choke out. Are you saying I should try and adjust the fuel screw (using the method you suggested) with the choke out, because the bike will not run without it on?

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I'd try a different pilot jet being you are positive the slide is unbroken and is not upside down nor has the slow air jet been changed..

Have you a #45 pilot in perfect condition you can try? A choke (actually, it is an enricher) adds both fuel and air to the mix and may be masking the problem.

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I have an 08 wr450f with following mods:

removed grey wire

throtle stop (from GYTR kit)

08 YZ450f exhaust

main jet--168

pilot jet--48

leak jet--45

main air jet--110 (from GYTR kit)

needle--NFLQ 4th from top

GYTR fuel screw--2 turns out (yes I checked spring, washer, and o-ring)

this is my jetting

Year: 2009

Model (400 - 426 - 450): 450

Cam Timing (WR/YZ): WR

Main jet: 165

Pilot Jet: 48

PAJ: Stock

Leak Jet: 45

Starter Jet: Stock (don't know what size it is)

Fuel screw (turns out): 1.5

Needle Model/Clip position: JD Red needle 5th clip

Grey Wire Mod (Y/N): Y

TPS Connected (Y/N): Y

Airbox Snorkel/Lid (on or off): off

AIS Removed (Y/N): Y

Airfilter Brand: Stock

Exhaust Brand: Stock (removed the little pee pee from the exhaust)

Average Altitude: 800-1600

we are both in ohio.... mine runs perfect.... only thing is you got the YZ exhaust...... I didnt touch any main air jet...my main is 165 and yours is 168...... i am running my needle in the 5th clip and you are onthe 4th clip......my screw is out 1.5 turns.....

those are our differences.... maybe try going to what mine is jetted like

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-when I release the hot start the idle drops very low and when I apply the hot start the idle return to normal range.

-released the hot start, the idle drops very low, let it warm up, but as soon as I push in the choke it still dies.

- Removing hot start richens, needing hot start means too rich.

- Removing choke leans, running with choke means too lean

I'm stumped, but it has to be something simple.

I solved the problem (with everyones help)...and YES it was simple but very very stupid as well :busted:. When I was adjusting the fuel screw I turned the idle down too low and stalled the bike. When I went to turn the idle back up it still would not start...I must of gotten confused because I then turned it the other way (turning it down). It obviously didnt start so I continued turning it (down) trying to get it to start. I ended up turning it down so far the idle screw was nowhere near engaging the throttle shaft.This is why the idle adjustment screw had no effect on the idle and why the choke needed to be on for the bike to run!

And the hot start lever needs to be in because the pilot circuit is too rich. After taking care of the idle I went to fine tune the fuel screw (thanks to William1 for posting this method many times for us newbies) and sure enough the fuel screw has no effect on the idle so it is too rich.

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