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trancetechau

How do I set the fuel screw

8 posts in this topic

Noob question. But I can't for the life of me work out how to set the fuel screw. I know 1 1/2 turns is the starting point but my issue is I'm not sure where 0 turns is? If I turn the adjustable fuel screw either way clockwise or anti-clockwise looking at it from the clutch side of the bike it just keeps turning. I would have thought it would turn and tighten up like a nut and bolt?

Please explain???

WR450F 2009 - Australian version.

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It should bottom out when turning clockwise and come loose turning counter clockwise. You need to turn it clockwise until it stops the 1.5 turns out. Not sure what you have going on. Are you sure you are actually spinning the screw?

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It should bottom out when turning clockwise and come loose turning counter clockwise. You need to turn it clockwise until it stops the 1.5 turns out. Not sure what you have going on. Are you sure you are actually spinning the screw?

I'm turning either way can turn 6+ full rotations and i can't feel anything tightening up. I had the adjustable screw installed by a shop when I got the bike (new) they stuffed up other things. Is it possible that it's not installed correctly or is the wrong screw or something for my bike?

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If you can continually turn it without tightening or coming out then the threads must be stripped.

Does turning it change the way the engine runs?

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If you can continually turn it without tightening or coming out then the threads must be stripped.

Does turning it change the way the engine runs?

2007_Sunline_Fuel_Mixture_Screw.jpg

thats the fuel screw I have.

Yes it does change the way it runs. On the weekend my bike wouldn't start - i was riding in a different place 5 hrs away from where I normally ride. To get it going I screwed the fuel screw in 1 full turn and the bike started. I played around with the fuel screw a bit and noticed that it just kept screwing which I thought was strange. So I am curious why it keeps spinning. I'm guessing I will have to readjust again this weekend riding in my normal area so want to make sure I know what to do. So it should not continually spin?

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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. Do it with the bike fully heated up.

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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His screw sounds like what happened to mine not to long ago... tilt the carb over and pull the screw out..chances are it's only turing in the O ring...it's not in the threads... mine did this not to long ago...on a rainy day no less. not fun... anotehr thing that happens is some folks have turned the screws in to hard and fast and smashed the point in on the screw. So best bet is pull it out and check it out.

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