KX250F Engine Running Issue

MicMcDude375
Hey guys. So I replaced the cylinder and piston in my 2012 KX250f and when I went to start it up, the engine would fire and run for 10 seconds or less before stopping. Does anyone have any ideas on what might cause this? My first thought is the timing might be slightly off, but I thought I would ask around and do some research before I go crazy looking for the problem.
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Paw Paw 271
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Paw Paw 271 12/29/2017 7:23am
12/29/2017 7:23am
How long did the bike set from the last running before tear down until it was rebuilt and fired back up?
Have you checked the fuel pump and filter?
Have you cleaned the injector?
Have you checked to see that all electrical connections are plugged it and clean?

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Acidreamer
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Acidreamer 12/29/2017 7:26am
12/29/2017 7:26am
Did you remove the tip over sensor and install it upside down? Its easy to do and will cause the bike to run for a few seconds and stop
MicMcDude375 12/29/2017 9:48am
12/29/2017 9:48am
The bike sat for close to a year between tear down and starting back up.
I did check the injectors and electrical connections, but did not check the fuel pump or filter so I will give those a look along with another once over of the rest of the fuel system.
The tip over sensor was removed so I will double check that as well.

Thanks for the places to start looking.
Paw Paw 271
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Paw Paw 271 12/29/2017 9:51am
12/29/2017 9:51am
Plan on cleaning the injectors as they do not like dried gas.

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FGR01
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FGR01 12/29/2017 10:07am
12/29/2017 10:07am
Verify cam timing.
pCp 252
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pCp 252 12/29/2017 2:04pm
12/29/2017 2:04pm
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the pump apart, it doesn’t go back together.

Since we’re on the subject...
I’ve got a 2014 KX250F that’s been apart for a year and getting ready to be built this winter. The fuel injectors have been stored in plastic baggies, but what’s the process of cleaning them?

Spraying them down with a solvent like carb cleaner? I believe I’ve seen a special tool that flushes them in automotive applications, but i don’t know if that applies with MX bikes. Thanks.

BobPA
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BobPA 12/29/2017 8:51pm
12/29/2017 8:51pm
pCp 252 wrote:
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the...
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the pump apart, it doesn’t go back together.

Since we’re on the subject...
I’ve got a 2014 KX250F that’s been apart for a year and getting ready to be built this winter. The fuel injectors have been stored in plastic baggies, but what’s the process of cleaning them?

Spraying them down with a solvent like carb cleaner? I believe I’ve seen a special tool that flushes them in automotive applications, but i don’t know if that applies with MX bikes. Thanks.

9V battery with two test leads will hold the injector open. Blow carb cleaner through it both ways.
Paw Paw 271
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Paw Paw 271 12/29/2017 9:21pm
12/29/2017 9:21pm
pCp 252 wrote:
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the...
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the pump apart, it doesn’t go back together.

Since we’re on the subject...
I’ve got a 2014 KX250F that’s been apart for a year and getting ready to be built this winter. The fuel injectors have been stored in plastic baggies, but what’s the process of cleaning them?

Spraying them down with a solvent like carb cleaner? I believe I’ve seen a special tool that flushes them in automotive applications, but i don’t know if that applies with MX bikes. Thanks.

BobPA wrote:
9V battery with two test leads will hold the injector open. Blow carb cleaner through it both ways.
x2

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Acidreamer
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Acidreamer 12/30/2017 5:52am
12/30/2017 5:52am
pCp 252 wrote:
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the...
The fuel pumps filter is not easily serviceable, there is a page on thumpertalk that goes through the process but it seems incentive you’ve taken the pump apart, it doesn’t go back together.

Since we’re on the subject...
I’ve got a 2014 KX250F that’s been apart for a year and getting ready to be built this winter. The fuel injectors have been stored in plastic baggies, but what’s the process of cleaning them?

Spraying them down with a solvent like carb cleaner? I believe I’ve seen a special tool that flushes them in automotive applications, but i don’t know if that applies with MX bikes. Thanks.

Ultrasonic cleaner for injectors

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