Crf450r 2007 running lean

Bailey_Beista
Edited Date/Time 2/9/2020 11:30pm
Hey I'm new to 4 stroke engines this is the second 4 stroke I have rebuilt and I understand the shims timing etc.. But after a ride the bike high idles and same when I pull the clutch in, many people online say its a lean condition so I open the fuel screw on the bottom of the Carb and not much changes still have a high idle. I want to add it only for about a minute or 2 then the rpm drops back to normal. Then you rev again and the rpms stay high and then return. Maybe a sticky throttle cable? Or should I do some larger jets for my Carb?
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Paul_Pitzonka
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Paul_Pitzonka 2/9/2020 9:20am
2/9/2020 9:20am
Could be an air leak, but It more than likely sounds like a lean pilot condition... if it started out of the blue more than likely a dirty pilot jet... if not then step up the pilot size until the fuel mixture screw has an effect on idle rpm...
FGR01
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FGR01 2/9/2020 2:49pm
2/9/2020 2:49pm
These bikes can suck air at the exhaust header crush washer or at the carb to head boot. They can also suck air at the o-ring on the carb cap. Also make sure the plate on the front of the carb slide is installed correctly.

Make sure the hot start plunger in the carb is clean and greased, operating smoothly and closing completely and there is a little play in the cable. If this hangs open a little it will suck air and high idle. They tend to get gunked up with dirt and corrosion.

As said above, plugged up pilot jet or dirty fuel screw passage can do this. Verify all jetting is stock or close to stock as the 2007 jetting was pretty good. Make sure someone didn't throw something super lean in there at some point.
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omalley
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omalley 2/9/2020 3:26pm
2/9/2020 3:26pm
Agree with the others, and as FGR said, don’t overlook the plate on the slide...it’s had to explain but it looks more correct when it’s actually upside down. I fought that one years ago after cleaning my carb. It’ll frustrate the hell out of you until you find it.
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Bailey_Beista 2/9/2020 11:29pm
2/9/2020 11:29pm
omalley wrote:
Agree with the others, and as FGR said, don’t overlook the plate on the slide...it’s had to explain but it looks more correct when it’s actually...
Agree with the others, and as FGR said, don’t overlook the plate on the slide...it’s had to explain but it looks more correct when it’s actually upside down. I fought that one years ago after cleaning my carb. It’ll frustrate the hell out of you until you find it.
I will have a look after work today, I know what you mean about the slide because I put it in wrong the first time so I'm pretty sure it's okay at the moment. The thing I can think is causing a air leak is that I removed the hot start because I changed the clutch perch so just plugged the black cap and screwed that back onto the Carb

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Bailey_Beista 2/9/2020 11:30pm
2/9/2020 11:30pm
Thanks for the info guys, I will double check everything today it might be my hotstart because I removed it because I changed the clutch perch so just plugged the black cap and screwed it in

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