2011 kx450 cut out and won't start. Help!

[Mizzury44]

I had a race yesterday and the bike just cut out on the first lap and wouldn't start. It started for a second after a bunch of kicks then just died and when I got back home the bike would not start. I replaced the cam chain and tensioner 2 days before but there was no issue with the bike starting. So when I got back home I figured it jumped timing but it didn't it's dead on I even took everything apart and retimed it and it still won't start. Valves are in spec as well. So I pulled the fly wheel thinking it could of been that and nothing everything was installed correctly . Pulled the plug poured some gas down there and the bike would fire off so I know I'm getting spark. Anyone have any ideas would greatly appreciate it. Thank you. If you need any more information I'd Glady give it to you .

 

 

 

 

 

 

 

 

[Ryankx250]

If the bike will start when you put gas in the cylinder, then it's obviously a fuel delivery issue.  I'd start by checking the fuel pump to make sure that it's working.

[Mizzury44]

Thanks for the response. Now what's the easiest way to make sure the fuel pump is working properly never had to test one before.

[Duke_Moto]

  you can test the resistance of the fuel pump of the with a multimeter and compare it to manufacturer readings. But it could also be a clogged fuel filter restricting flow. Pouring gasoline into the combustion chamber through the spark plug hole isn't the best way to test if you receive spark. If you poured an excessive amount of fuel, it will pre detonate through compression, and may cause damage. one way to check if you have spark is to ground the plug onto the frame or engine and kick the bike over while the fuel system is disabled. you should se a spark jump from the center electrode to the outer electrode or ground strap. To make sure you are receiving a strong spark from the ignition coil, you would need to use a multimeter and test the resistance values of the ignition coil, and compare it to desired spec. However, there are more components in the system which would affect the strength of the spark. The most common component to fail first after the spark plug and wire is the ignition coil.

[Mizzury44]

Awesome man thanks for tips definitely didn't know it could cause damage. Won't ever test it that way again lol. I'm going to have some time tomorrow night to work on the bike. So I'm going to try what you guys are suggesting. Hopefully looking at it with some fresh eyes I'll be able to pin point it.

[Duke_Moto]

31 minutes ago, Mizzury44 said:

Awesome man thanks for tips definitely didn't know it could cause damage. Won't ever test it that way again lol. I'm going to have some time tomorrow night to work on the bike. So I'm going to try what you guys are suggesting. Hopefully looking at it with some fresh eyes I'll be able to pin point it.

No problem. The reason why it can cause damage is because the piston doesn't fully complete it's compression stroke where the crankshaft hasn't rotated to where it can be pushed down again freely (which is x degrees at TDC). (Combusted gasoline---><---piston) here's a little diagram which sorta explains it a bit easier. The arrows are the forces. (Combusted AF mixture---> piston--->) this is how it should be. Feel free to ask if you need anything else. Have a good one.

Edited November 19, 2018 by Duke_Moto

[Mizzury44]

[emoji106] thanks again. I'll touch base tomorrow and let you know!

[Mizzury44]

Think I found the problem haha. Just removed the tank and it wasn't even attached must of been fraying for awhile just never picked up on it. And when I pulled the take to do the cam chain probably gave out. What a bummer! Is that even fixable?! pulling it apart now.

[Mizzury44]

Well I managed to get it out. Before I stripped the pump I ran a 12v battery to what little I had left of those wires and the pump is operating correctly. Just wanna try to find a junk fuel pump and strip that part off .

[Duke_Moto]

5 hours ago, Mizzury44 said:

Think I found the problem haha. Just removed the tank and it wasn't even attached must of been fraying for awhile just never picked up on it. And when I pulled the take to do the cam chain probably gave out. What a bummer! Is that even fixable?! pulling it apart now.

Nice job! That will for sure do it, and you didn't need to do too much work it seems. It is possible to repair that, but it mig by take a bit of work. But  you'd want to make sure that the wires do not have any build up on them which would cause unwanted resistance. Secondly, you want to find out how it happened so it doesn't continuously occur if possible.

Edited November 21, 2018 by Duke_Moto

[Mizzury44]

Yeah didn't take me to long lol. I really don't wanna try to repair that won't look good cause the wires are incased in like a solid plastic. Found a guy with a junk 2012 kx250f fuel pump. The wiring looks identical so I figured if I just swap the wiring I'd be in business . I'll get back to yeah and let you know how it works out. Definitely looking to buy a new fuel pump or even a pre-owned prices are crazy! Thanks again

[Mizzury44]

[Mizzury44]

Well I have a extra fuel pump coming bought one dirt cheap with a broken fuel connection with a working pump just going to swap the wiring and I'll be in business . But I got curious if I could make this work in the mean time. So I slowly melted the plastic off with a flat head screwdriver. And I was able to get the connectors off and expose the tongs. So I'll rewire it with solder and heat wrap. And I'll post and update when I get it back together.

[Mizzury44]

Nice job! That will for sure do it, and you didn't need to do too much work it seems. It is possible to repair that, but it mig by take a bit of work. But  you'd want to make sure that the wires do not have any build up on them which would cause unwanted resistance. Secondly, you want to find out how it happened so it doesn't continuously occur if possible.

Yeah really think the issue was negligence on my part maybe I set the tank down the wrong way not even realizing I was kinking the wires. Definitely a way to learn the hard and to know and be mindful of how I'm setting the gas tank down that's for sure. I appreciate all your help and the pointers!

[Duke_Moto]

3 hours ago, Mizzury44 said:

21 hours ago, Duke_Moto said:

Nice job! That will for sure do it, and you didn't need to do too much work it seems. It is possible to repair that, but it mig by take a bit of work. But  you'd want to make sure that the wires do not have any build up on them which would cause unwanted resistance. Secondly, you want to find out how it happened so it doesn't continuously occur if possible.

Yeah really think the issue was negligence on my part maybe I set the tank down the wrong way not even realizing I was kinking the wires. Definitely a way to learn the hard and to know and be mindful of how I'm setting the gas tank down that's for sure. I appreciate all your help and the pointers!

No problem. If you need anything else, feel free online ask.

[Mizzury44]

This is were I'm at now. Managed to reuse the old adapters. Just opened them up twisted the wire in and soldered them together. I'm going to shrink wrap them now. Cause I tested to make sure the pump will activate with a 12v battery and it did. So heat wrap and epoxy and I think I should be good to granted I'm swapping the wiring when the other pump comes in. Just wanted to see if it's possible to rig the wiring for a permanent fix. It looks horrible but it works. I'll show a finished product when I'm done .

[Mizzury44]

Success!!! Got it all back together bike fired right up now I can go eat my Thanksgiving dinner lol. I used 3 layers of heat shrink rap 2 on each of the wires and the 3rd was to cover over everything. Then a layer of electrical tape and I sealed everything in with silicone. Also I put dilectric grease on the connections. Definitely think it would hold up for a long period of time. Anyways fun little experiment! And a lesson to never set your tank down on your wires. Take care and if anyone has any questions feel free to ask. Thank you!