2016 250sxf won't start

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4/27/2017 9:52 AM
Edited Date/Time: 4/27/2017 2:40 PM

Recently rebuilt the top end on my bike at 35 hours.
Started up right away all good and everything. Rode it around for a bit before I raced it a few days later..
Went out for first practice and it ran great.
Went out for last chance and I stalled it in staging and it wouldn't start. Took the tank off and disconnected the fuel pump and re connected it and it started. Then the following day I went to start it in the morning and it wouldn't. Ended up having to bump start it. Then it ran/ started fine the rest of the day.
Next day it ran great for the day.. recently started it to load it and then shut it off. Tried starting it not long after and it wouldn't start. Turns over great but won't fire.. valves are all in spec, just can't figure it out

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4/27/2017 10:09 AM

Try race gas

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

4/27/2017 10:20 AM

Id check valves but that's just me

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4/27/2017 10:39 AM
Edited Date/Time: 4/27/2017 10:40 AM

Check the kill button (disconect) , then all electrical conections

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4/27/2017 12:01 PM

Already run race gas.
Got it to run when I loaded it but after I shut it off loading it up I tried to start it not long after, it wouldn't start. Haven't tried since.. seems to be when it stalls it doesn't want to start. Only a few things I had to disconnect when I rebuilt it, those all are connected so I have no clue what It could be.

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4/27/2017 12:12 PM

Take the plug out and see if it's getting fire. If it's not getting fire your throttle position sensor is probably bad.

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4/27/2017 12:40 PM

most likely a bad TPS or intake air temp sensor. also, get a mechanical cam chain tensioner. those hydraulic units are a nightmare waiting to happen.

double check cam timing, then move to sensors.

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4/27/2017 1:20 PM

Do you have a stock battery?

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4/27/2017 1:28 PM

Do you use the proper starting procedure?

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4/27/2017 1:35 PM

Are the plugs wet? Could possibly be opening the throttle when you stall or try to start and get too much fuel.

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

4/27/2017 2:40 PM

Cam timing was spot on. Both dots on the cams were next to each other and level with the head. Made sure it was on TDC as well..
battery is still stock and fully charged
Always have used that starting procedure.
Is there a code that would flash on the light if it was the TPS
Just went out at started it. Started right away, shut it off and it started right up. On purpose I stalled it cause it seemed to be when it stalled it wouldn't start, didn't want to for a few min but now it did..

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4/27/2017 2:44 PM

Put in a new little inline filter in the quick connect.

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4/27/2017 3:22 PM

Just put a new inline filter in the quick connect. Once I started it I went to push the throttle forward to turn the choke off. And it doesn't disengage the choke anymore. Could that have something to do with it?

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4/27/2017 3:26 PM

might be a stretch, but on my 350 and a buddy's 450, the ground screw came out and it'd do the same thing. Might be dumb suggestion or too simple, but check that screw in the rear fender coming off the battery and make sure it isn't loose or missing.

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4/27/2017 3:29 PM

sounds like loose sprocket bolts to me bro

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4/27/2017 3:52 PM

gaberas225 wrote:

Just put a new inline filter in the quick connect. Once I started it I went to push the throttle forward to turn the choke off. And it doesn't disengage the choke anymore. Could that have something to do with it?

The choke needs to be pulled out to be off.

Could be the tip over sensor or maybe just a kinked line on your fuel pump. You can take the pump out and see if your lines are smooth.

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4/27/2017 4:03 PM

I had the wire in the white molex plug for the starter switch behind the front number plate get corroded. It started to want to start intermittently. Also the injectors used to get clogged but I think they fixed that issue with injectors with different spray patterns. Good luck

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4/27/2017 5:52 PM

Ok, you can be really honest about how you REALLY feel, bro. How about "2016 250 SXF won't F'ING start!

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"If you are going through HELL, keep going."-Winston Churchill
"A man needs a little madness or else he never dares cut the rope and be free"-Zorba
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4/27/2017 5:56 PM

oldblood wrote:

Ok, you can be really honest about how you REALLY feel, bro. How about "2016 250 SXF won't F'ING start!

Haha, pretty upset bout it, things been great up until now. Wishing I would have got a 250 2 stroke now.
Tried a few things. Guess we will see what happens this weekend. Hoping to get it all figured out before next weekends race.

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4/27/2017 6:05 PM

I'll get shit for this but, try draining ALL the fuel and try 91 pump gas. Some bikes are finicky.

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"If you are going through HELL, keep going."-Winston Churchill
"A man needs a little madness or else he never dares cut the rope and be free"-Zorba
Blur the technicolor

4/27/2017 6:13 PM
Edited Date/Time: 4/27/2017 6:13 PM

Otherwise probably an electronic connector. Or a wire grounding.

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"If you are going through HELL, keep going."-Winston Churchill
"A man needs a little madness or else he never dares cut the rope and be free"-Zorba
Blur the technicolor

4/27/2017 6:37 PM

Pull the Fuel pump out of the tank. Good chance that your supply line is kinked at a 90, which results in the fuel filter cracking under pressure. You loose pressure and eventually the pump dies

Happened on my bike, and 4 others I know of.

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4/27/2017 8:04 PM

Jack_Wagon wrote:

Take the plug out and see if it's getting fire. If it's not getting fire your throttle position sensor is probably bad.

There are a lot of different suggestions in here.

Start with the simple things, and keep very good track of what you check/try.

Like Jack Wagon suggested, I'd check the spark first the next time the problem manifests itself.

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4/27/2017 8:31 PM

As I understand it, octane relates to timing, (and compression ). The higher the octane, the sooner the spark needs to be. Okay, I'm really putting myself out there for criticism, but, doesn't the octane need to match the timing /compression? Not saying that is the problem here, but.

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"If you are going through HELL, keep going."-Winston Churchill
"A man needs a little madness or else he never dares cut the rope and be free"-Zorba
Blur the technicolor

4/27/2017 9:01 PM

Thanks guys for the ideas, will have to try a few out, already tried some, should be interesting to see how it runs this weekend.

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4/27/2017 11:30 PM

Because you stated that you can always bump start it, that says to me that the kill switch isn't bad and it's getting spark and fuel.
It could be fuel delivery, but that doesn't make much sense either because it runs if you bump start it.

I'm thinking it might simply be flooded.
If so, hold the throttle wide open and crank it over for about 5 seconds.

Also, is it really a problem only when you stall it or is it actually a problem when it's already warmed up?
If it's the latter, than it points to the choke staying open.

Good luck!

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4/28/2017 5:58 AM

Radical wrote:

Because you stated that you can always bump start it, that says to me that the kill switch isn't bad and it's getting spark and fuel.
It could be fuel delivery, but that doesn't make much sense either because it runs if you bump start it.

I'm thinking it might simply be flooded.
If so, hold the throttle wide open and crank it over for about 5 seconds.

Also, is it really a problem only when you stall it or is it actually a problem when it's already warmed up?
If it's the latter, than it points to the choke staying open.

Good luck!

Only time it's a problem is when it's warmed up and it's been stalled.

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4/28/2017 6:29 AM
Edited Date/Time: 4/28/2017 6:58 AM

Radical wrote:

Because you stated that you can always bump start it, that says to me that the kill switch isn't bad and it's getting spark and fuel.
It could be fuel delivery, but that doesn't make much sense either because it runs if you bump start it.

I'm thinking it might simply be flooded.
If so, hold the throttle wide open and crank it over for about 5 seconds.

Also, is it really a problem only when you stall it or is it actually a problem when it's already warmed up?
If it's the latter, than it points to the choke staying open.

Good luck!

gaberas225 wrote:

Only time it's a problem is when it's warmed up and it's been stalled.

It sounded like heat was a common denominator. So I was starting to think the stator could be going bad, but you said it wouldnt start first thing in the morning too. So, that reduces the chances of it being heat related electronics issues.

Anytime I had problems with a four stroke not wanting to start, and it would by push starting it, valves were the culprit.

Also, have you tried clearing the cylinder before hand?

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Copius pattern amounts of phrases like “Anyone have”..., “Anybody know?”.... and their variations.

Thoughts?
Any help is appreciated!
Thanks in advance!





4/28/2017 7:37 AM

It was only that one day it didn't want to start first thing in the morning, the rest of the day it was fine. The following day it started good and ran all day. Valve clearances were in spec when I took it apart. Made sure they were in spec when I put it back together as well. Was weird because it never did this before I rebuilt it.

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4/28/2017 8:47 AM

I would pick up a WPS Featherweight battery... You'll be surprised how easy your bike starts even when it's cold. Stock battery is junk. Even after 4 new part numbers, still is junk. If it's under 60 degrees overnight, the stock battery can't power the fuel pump until you "warm it up." WPS one has 30% more CCA and fires up instantly every time. They finally put a new battery in the 17 factory editions, so hopefully that helps in the future.

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