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VERY hard starting 2010 CRF450 after winter tear down

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ok this is a weird one, but I'm stumped.  Just got it all back together after winter tear down and was going to take it out for a quick ride, and the bike will not start, i kicked and kicked and nothing, it will backfire very loudly once every 5-10 kicks, but will not fire.  I took the plug out, has fuel on it and checked spark and its good.  Then randomly kicked it over again and it fired, ran, and idled.  Took it out for a ride and had all the power it had before, so thought it was fixed.  Then tried to start it again tonight and it would not fire at all.  This is beyond frustrating and I'm hoping someone has had this issue and know the fix.  Also put a new plug it in and that still didn't fix it.  Any help is much appreciated folks.

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When you "tore it down" for winter did you drain every last bit of fuel out of it? Did you add stabil to the fuel and leave it in the bike during winter? Have you checked the fuel filter/pump?

 

Obviously it is getting fuel but is the fuel delivered correctly? Is it still good usable fuel?

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its got fresh fuel in it, and I drained it all out of the tank before the winter.  I did not tho drain the pump itself.  How hard is it taking it apart and cleaning it?  I have done a lot of carbs but this is my first fuel injected bike.  Also where would the fuel filter be located on this bike, first tear down on it too

 


Also on the fuel pump end, is there a way to test it to see if its fine?

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The pump and filter are all located in the tank. Look at the bottom of the tank. You will see a circle of bolts, that is the pump and filter. The filter would need to be replaced. The pump can be bench tested with a 12v source. If the pump itself is clogged with coagulated fuel it may also need to be replaced but don't quote me on that. See the link below for the parts schematic

 

http://www.partzilla.com/parts/search/Honda/Motorcycle/2010/CRF450R+A/FUEL+TANK+%281%29/parts.html

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The decompression lever might be hanging the valve open.

Sometimes the return spring gets &%$#@!ed up if your not careful when you reassemble the cam. Or you might be tight on your valve clearance.

Or you &%$#@!ed up the valve and its not closing.

Did you do anything to the head while you had it apart?

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Or maybe your off 1 tooth on the cam timing.

or if the valves hit the piston before you took it apart then its likely the cam sprocket spun out of time on the cam. \

 

How about some more info

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motor was never apart this winter, haven't had the motor apart besides checking valves since i bought the bike last year.  Also one other piece of info, when i was attempting to pull the O2 censor from its wiring harness i accidentally pulled the two wires from its grommet.  I put them back in the way I thought it was from stock, but I'm not sure and there isn't anything in my shop manual as to what way they go in.  Would that cause an issue?

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WHatever your calling an o2 sensor is wrong there isnt one

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well whatever goes into the air box, that sensor I'm not sure if it is wired properly

 

also just took the filter off of pump, clen, and bench ran the pump, fine, with the harness attached and fuel in it after a assembled it again

 

does the sticking of the auto decomp happen often?  where else should i be looking

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Its probably not the fuel pump. That's not typically a symptom of backfiring.

 

check for metal shavings around the coil triggers at the flywheel

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well whatever goes into the air box, that sensor I'm not sure if it is wired properly

 

also just took the filter off of pump, clen, and bench ran the pump, fine, with the harness attached and fuel in it after a assembled it again

 

does the sticking of the auto decomp happen often?  where else should i be looking

 

It'd start even if it was unplugged. It'd just blink the kill button when it ran. If it sat with no fuel in it for a long time, you could try this

 

Id have you go over all the connections. There's a dirty one, somewhere, where it counts. Or the condensor just took a shit.

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Thats my plan for tomorrow, grounds and cleaning connections.

How many grounds are there that are accessible to remove and clean and reinstall?

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Thats my plan for tomorrow, grounds and cleaning connections.

How many grounds are there that are accessible to remove and clean and reinstall?

 

Just one, but Id check the connections at the condensor and AIT. Seems like those are the ones that get messed up because of where they're located.

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ok checked the AIT connection, checked and clean, took off the condensor connection, and installed a battery in place of condenser to see if that will start it, it back fires a ton, and i can hear the fuel pump running, but still will not start, is there anywhere else to try?  from what I've read even if you plug a battery in for the condenser that gets it going.  Can the fuel pump still be bad even tho i can hear it run?  Whats my next step here?

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The pump may be spinning up, but is it delivering the correct amout of fuel? You my need to do a pressure test on it. Also, the filter may be clogged?

 

Check the 2 threads I linked below. May be some info in them that could help

 

http://www.thumpertalk.com/topic/1043654-2009-crf450-starting-woes-help-please/?hl=%2Btest+%2Bfuel+%2Bpump#entry11089955

http://www.thumpertalk.com/topic/843963-2009-crf-450-wont-stay-running/?hl=%2Btest+%2Bfuel+%2Bpump#entry8742909

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No, backfiring does not sound like a fuel pump but that does not 100% rule it out. Have you had the valve cover off and checked the valve clearance? Have you checked the timing?

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The kill switch can be disconnected to rule that out.

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