2010 Kx450f has me baffled.

GingerVision87
2010 Kx450f. Let me preface this by saying, yes valves are in spec, yes the timing is spot on, yes the compression is good, yes it is getting bright blue spark, yes capacitor is new, yes fuel pump is new, and yes all o rings in fuel pump and fuel filter is new. Now...
Bike will start after 5 kicks. Kill it. It will start after 3. Kill it. Will never start again, nothing, not a backfire, not a sputter. Unplug fuel line to injector, reinstall, will immedialy fire right back up and will run all damn day perfectly. Kill it, will start in 3 kicks. Kill it. Will never even attempt to start again until you unplug fuel line from injector and reinstall. Hot or cold it does not matter, same shit at any temp. What the actual hell is going on.
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Paw Paw 271
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Paw Paw 271 9/24/2019 5:47am
9/24/2019 5:47am
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced air back in and thus it will start and run until the same thing repeats.
To test this....Try running the bike with the fuel tank cap loose.

Paw Paw
CarlinoJoeVideo
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CarlinoJoeVideo 9/24/2019 6:19am
9/24/2019 6:19am
Paw Paw 271 wrote:
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced...
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced air back in and thus it will start and run until the same thing repeats.
To test this....Try running the bike with the fuel tank cap loose.

Paw Paw
I can see your thinking here but what about the times when he gets it to run and it’s fine all day?
kb228
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kb228 9/24/2019 7:01am
9/24/2019 7:01am
Try it without the gas cap. There might be enough power at the pump while the bike is running to get gas but not enough from kicking it.
Paw Paw 271
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Paw Paw 271 9/24/2019 7:15am
9/24/2019 7:15am
Paw Paw 271 wrote:
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced...
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced air back in and thus it will start and run until the same thing repeats.
To test this....Try running the bike with the fuel tank cap loose.

Paw Paw
CarlinoJoeVideo wrote:
I can see your thinking here but what about the times when he gets it to run and it’s fine all day?
Did I miss that in his statement?

Paw Paw

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CarlinoJoeVideo
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CarlinoJoeVideo 9/24/2019 8:35am
9/24/2019 8:35am
Paw Paw 271 wrote:
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced...
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced air back in and thus it will start and run until the same thing repeats.
To test this....Try running the bike with the fuel tank cap loose.

Paw Paw
CarlinoJoeVideo wrote:
I can see your thinking here but what about the times when he gets it to run and it’s fine all day?
Paw Paw 271 wrote:
Did I miss that in his statement?

Paw Paw
"Unplug fuel line to injector, reinstall, will immedialy fire right back up and will run all damn day perfectly. "
GingerVision87 9/24/2019 11:38am
9/24/2019 11:38am
Paw Paw 271 wrote:
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced...
Fuel tank cap is not venting correctly and causing a vacuum that will stop fuel flow. When you break the fuel line loose to have introduced air back in and thus it will start and run until the same thing repeats.
To test this....Try running the bike with the fuel tank cap loose.

Paw Paw
CarlinoJoeVideo wrote:
I can see your thinking here but what about the times when he gets it to run and it’s fine all day?
Paw Paw 271 wrote:
Did I miss that in his statement?

Paw Paw
Yessir, that is what is so strange. I don't believe it's a vaccum building in the tank, because pulling the line from the bottom of the tank won't let air in, the same way it won't let fuel out if the bike is not running. Has an electronic check valve on the pump. Once I get it started, you can ride for an hour straight. But if I kill it, tank must be unplugged and replugged to the fuel line before starting again. I just don't understand.
GingerVision87 9/24/2019 11:49am
9/24/2019 11:49am
Also, I not only have to unplug and replug, I have to dump the fuel from the line out and then replug. What on Earth. But yes when it's running it stays running as long as you want flawlessly.
kb228
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kb228 9/24/2019 12:05pm
9/24/2019 12:05pm
Just a theory.. when the line is full, is it allowing too much gas in right at start up causing it to be too rich to start - due to an injector malfunction? Then once you empty it, the only thing going in is air for that split second allowing it to start?

Can you bump start it after it wont restart?
GingerVision87 9/24/2019 12:14pm
9/24/2019 12:14pm
kb228 wrote:
Just a theory.. when the line is full, is it allowing too much gas in right at start up causing it to be too rich to...
Just a theory.. when the line is full, is it allowing too much gas in right at start up causing it to be too rich to start - due to an injector malfunction? Then once you empty it, the only thing going in is air for that split second allowing it to start?

Can you bump start it after it wont restart?
Thanks for the input. I will get it to the point it needs the line pulled and won't start and then attempt to roll start and report back.
GingerVision87 9/24/2019 2:29pm
9/24/2019 2:29pm
Reporting back. No...will not roll start when it shuts off either until line is pulled and drained
Paw Paw 271
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Paw Paw 271 9/24/2019 3:22pm
9/24/2019 3:22pm Edited Date/Time 9/24/2019 3:26pm
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the vacuum issues I stated. The small amount of air that would reenter the fuel line would be very small.
I would also look at a leaking fuel injector as a possible issue as well as it can cause flooding while setting, but in most cases that would happen over night.....
Hot fuel. You may want to try to insolate the under side of the fuel tank to make sure it is not vapor locking.
Try running it with the fuel cap off or loose and see if it will restart , first.

Paw Paw
GingerVision87 9/24/2019 6:25pm
9/24/2019 6:25pm Edited Date/Time 9/24/2019 6:25pm
Paw Paw 271 wrote:
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the...
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the vacuum issues I stated. The small amount of air that would reenter the fuel line would be very small.
I would also look at a leaking fuel injector as a possible issue as well as it can cause flooding while setting, but in most cases that would happen over night.....
Hot fuel. You may want to try to insolate the under side of the fuel tank to make sure it is not vapor locking.
Try running it with the fuel cap off or loose and see if it will restart , first.

Paw Paw
Paw Paw, When I unplug the fuel line, there IS fuel coming out, (from the line, not the tank, as it shouldn't when not running) and as a matter of fact I have to dump the fuel out of the line before plugging it back in before it will start. I have tried with gas cap off and no difference. (I can also blow through the cap easily both ways). So I have ruled out the vapor locking in the tank. I do however fancy your idea about a leaky injector.. I will pull the throttle body and let it sit for a bit and see if it yeilds any fuel leaking. Thanks for your input everyone!
CarlinoJoeVideo
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CarlinoJoeVideo 9/24/2019 6:32pm
9/24/2019 6:32pm
Paw Paw 271 wrote:
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the...
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the vacuum issues I stated. The small amount of air that would reenter the fuel line would be very small.
I would also look at a leaking fuel injector as a possible issue as well as it can cause flooding while setting, but in most cases that would happen over night.....
Hot fuel. You may want to try to insolate the under side of the fuel tank to make sure it is not vapor locking.
Try running it with the fuel cap off or loose and see if it will restart , first.

Paw Paw
GingerVision87 wrote:
Paw Paw, When I unplug the fuel line, there IS fuel coming out, (from the line, not the tank, as it shouldn't when not running) and...
Paw Paw, When I unplug the fuel line, there IS fuel coming out, (from the line, not the tank, as it shouldn't when not running) and as a matter of fact I have to dump the fuel out of the line before plugging it back in before it will start. I have tried with gas cap off and no difference. (I can also blow through the cap easily both ways). So I have ruled out the vapor locking in the tank. I do however fancy your idea about a leaky injector.. I will pull the throttle body and let it sit for a bit and see if it yeilds any fuel leaking. Thanks for your input everyone!
Do you have a friend with the same bike and can try his tank? Wondering if it’s just a weird fuel pump issue?
GingerVision87 9/24/2019 6:44pm
9/24/2019 6:44pm
Paw Paw 271 wrote:
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the...
When you unplug the fuel line and there is no fuel coming out...I would still suggest that the fuel cap is the issue due to the vacuum issues I stated. The small amount of air that would reenter the fuel line would be very small.
I would also look at a leaking fuel injector as a possible issue as well as it can cause flooding while setting, but in most cases that would happen over night.....
Hot fuel. You may want to try to insolate the under side of the fuel tank to make sure it is not vapor locking.
Try running it with the fuel cap off or loose and see if it will restart , first.

Paw Paw
GingerVision87 wrote:
Paw Paw, When I unplug the fuel line, there IS fuel coming out, (from the line, not the tank, as it shouldn't when not running) and...
Paw Paw, When I unplug the fuel line, there IS fuel coming out, (from the line, not the tank, as it shouldn't when not running) and as a matter of fact I have to dump the fuel out of the line before plugging it back in before it will start. I have tried with gas cap off and no difference. (I can also blow through the cap easily both ways). So I have ruled out the vapor locking in the tank. I do however fancy your idea about a leaky injector.. I will pull the throttle body and let it sit for a bit and see if it yeilds any fuel leaking. Thanks for your input everyone!
CarlinoJoeVideo wrote:
Do you have a friend with the same bike and can try his tank? Wondering if it’s just a weird fuel pump issue?
I'm starting to think the same. I am going to check for a leaky fuel injector like paw paw suggested, but if that doesn't work I may just have to make the trip out and swap tanks. This fuel pump is brand new, however what is not new Is the pressure regulator on the pump housing. Maybe that's at fault...
GingerVision87 9/24/2019 10:39pm
9/24/2019 10:39pm Edited Date/Time 9/24/2019 10:41pm
I pulled the injector and I kicked it until line was fully pressurized and it squirts a good mist...never leaks, works as it should. This is killing me. This is the second night I'll probably be up until 4am working on this thing

I'm starting to think it's just somehow running too rich. And pulling the line allows it to clear the cylinder and lean it out long enough for it to start again. However cracking the throttle to start when it stops starting does nothing, which would be equal to pulling a hotstart...so nevermind. Ughh jezuz
kb228
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kb228 9/25/2019 4:05am
9/25/2019 4:05am
GingerVision87 wrote:
I pulled the injector and I kicked it until line was fully pressurized and it squirts a good mist...never leaks, works as it should. This is...
I pulled the injector and I kicked it until line was fully pressurized and it squirts a good mist...never leaks, works as it should. This is killing me. This is the second night I'll probably be up until 4am working on this thing

I'm starting to think it's just somehow running too rich. And pulling the line allows it to clear the cylinder and lean it out long enough for it to start again. However cracking the throttle to start when it stops starting does nothing, which would be equal to pulling a hotstart...so nevermind. Ughh jezuz
The kawi service manual specifically says to not start the bike with an open throttle because it will flood the engine. It still squirts fuel as if you were riding at open throttle.
CarlinoJoeVideo
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CarlinoJoeVideo 9/25/2019 7:23am
9/25/2019 7:23am
GingerVision87 wrote:
I pulled the injector and I kicked it until line was fully pressurized and it squirts a good mist...never leaks, works as it should. This is...
I pulled the injector and I kicked it until line was fully pressurized and it squirts a good mist...never leaks, works as it should. This is killing me. This is the second night I'll probably be up until 4am working on this thing

I'm starting to think it's just somehow running too rich. And pulling the line allows it to clear the cylinder and lean it out long enough for it to start again. However cracking the throttle to start when it stops starting does nothing, which would be equal to pulling a hotstart...so nevermind. Ughh jezuz
The only thing left is to try a different tank?
RGaede
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RGaede 9/25/2019 3:43pm
9/25/2019 3:43pm
Try another tank if available, it sounds like it's the pressure regulator, which is why i only ever would replace these pumps with oem. Cracking the throttle will squirt fuel, but if you think is flooded, holding the throttle wide open will shut off the injector (assuming the tps is working properly).
GingerVision87 9/25/2019 11:53pm
9/25/2019 11:53pm
Oddly enough, I can get it to start first kick five or six times by rolling the tps counterclockwise. I say oddly enough because I believe counter clockwise raises the tps voltage (more rich) and I was assuming it was too rich since I'm having to pull and drain the fuel line to start it. But then after five or six starts it's back to it's old ways and sure enough you'll have to pull the line and drain it again. Found a local guy (I live in the middle of nowhere) with the same bike but he apparently isn't a people person, said he wasn't interested in helping me....lol, so I'll be swapping with a buddy 3 hours away this weekend. If anyone has any more ideas throw them at me. I have built tons of carbed 250s and 450s and am well versed in everything Motocross, and have never been this stumped in my life. I was convinced I wanted an 18 450r but now I don't think another efi bike will ever be in my future.

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