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2015 yz 450f hard to start, won't idle but runs good

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So I have a 2015 Yz450f, the bike has around 20

hours on it. It has a tune on it from the dealership for more bottom end, the "sand/loam" tune. I have gone though it and cleaned the air filter and checked all the electrical connections. Messed with the idle a bit, but the bike does not want to start. It will start after maybe 5 mins of kicking, and I know you shouldn't give efi gas when starting but it will only start if you give it gas a little when kicking. Once it starts and you stay on the gas and don't let it idle it runs amazing, but you can't let it idle. I don't know where to start or what the problem could be, not sure if it's the tune or what? HELP

Edited by hunter11

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If you have not been filtering and treating your gas, you can expect the fuel pump filter to be clogged, and a struggling fuel pump, and possibly the injector nozzle to be dirty.

I am assuming you have checked already:

TPS connection and function

Spark plug / cap / coil / HT wire

'messed with the idle': you have to turn it COUNTER CLOCKWISE to raise the idle, the opposite of a carb. Turn it 5 clicks and see what happens

A passive reset should be done once you get it to idle: start it cold with NO throttle, and let it idle for 3 min with NO throttle, then shut it off, and restart and ride.

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Okay if it's something to do with fuel would it still run good once it's started? Because it runs great once it starts.

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 just this weekend I had the same issue. I started the bike and went to the line and when I let off the throttle and the bike quit. started it again and the same thing happened. Started it again and kept the throttle up and took off and it wanted to quit went I let off. went back to my truck and checked the fuel cap because it seemed like it was not getting enough fuel. I tried to start it and it started and would idle so I tried to ride it and it stopped again when I let off. I tried to start it again and it would idle so I went out on the track and it ran good when I got back to my truck and let off it quit. I thought I should try to turn the idle up so I started it and it would idle and I turned up the Idle a little and when I gave it gas it started missing and popping so I shut it off. I don't want to blow it up. Frustrated  It ran great the last time I rode.

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Confirmed it only has 28 hours in it, so I didn't think it would be valves but looked the intake valve was 0 so we shimmed it and problem solved runs great. Might need to put some steel valves in it in about 15 hours or so. I thought it was a pressure sensor on the air box but it was the valves.

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No other issues with it? My KX250F is having the same issue, I refuse to believe it's a valve clearance issue, it runs fine while the revs are up off idle a bit.

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On 5/30/2017 at 7:01 PM, hunter11 said:

Confirmed it only has 28 hours in it, so I didn't think it would be valves but looked the intake valve was 0 so we shimmed it and problem solved runs great. Might need to put some steel valves in it in about 15 hours or so. I thought it was a pressure sensor on the air box but it was the valves.

You should be able to get 100+ hours on that head. Someone has been pounding the rev limeter and not properly cleaning the air filter.....

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