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help with kx450f. bunch of questions, please help.

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Hey guys need a little tech help here. Just purchased a 2006 kx450f. Bike ran and started awesome up at 3500-4000 feet. But now that I'm home down at around 500 feet it doesn't want to start. It will start every once in a while. But then once I shut it off even when its already warmed up it won't start again. I don't know what jets are in the thing....what jets should I be running at 500 foot? It's a keihin fcr carb. And it also has a red knob sticking out of the bottom of the carb with 1,2,3,4 going around the knob. Some sort of adjustment i assume. What is it? And where should it be at? How many turns? But back to the starting problem. Why is it doing this? Is it 100% the jetting. When it does start it runs fine. Weird to me that it won't start again even when its hot. It has a hot start on the left side of the handlebars. What is the purpose of this? Someone please help me out by answering all of my questions. It's very aggravating when I just want to go ride. Thanks again.

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Anyone want to help a noob out? Trying to get this figured out. Sooner the better.

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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.

By the way, some people sleep at night and are not sitting online waiting for you to aska question.

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Why does it start sometimes but not other times? Especially why doesnt it start even after its hot?

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Why does it start sometimes but not other times? Especially why doesnt it start even after its hot?

There is a starting ritual to that motor. You need to figure it out for cold and hot starts.

Also, if you have not had your valves checked for clearance lately, then if they are out of spec, it will be hard to start, especially hot.

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