Kawasaki Dirt Bikes Forum

Ok so here's the deal. Bought a bike from a person that had it sitting in a garage for about a year or so. Got the Carb cleaned. Changed the plug. Changed the oil and filter. and i put new gas in it. When i first got it every time i would ride it about 20-25 minutes in to the ride it would die or kinda just bogg. So i took it to a local shop and had them rebuild the carb because i assumed there had been gas sitting in it while it was sitting in that persons garage for a while. So i got to the track today and it's doing the same thing..it would die then i would wait a few minutes and it would start then die again after a few minutes of riding. Raditior has fluid and water pump was also working fine..So i'm guessing it's an electrical problem? or float problem? I can't figure it out... I've had a few buddies check it out also and they have no idea either. Sorry for the story..I was trying to explain everything that was happening with it. Thanks for the help.....JB  
Pain is temporary, Glorys forever.

I'm ruling out electrical because it would be happening all the time not just when the bike warms up.  

What year KX?
What are your Jet Settings?
What plug?
What Pipe?
How old is the top end? (piston, rings, valves, timing chain)

It sounds like something is worn out enough to where you are losing seal/ pressure in the cylinder after the bike starts to get hot.  

Lets hope someone with more modern fourstroke experience joins in.  

Bill H. 2000 CR250R

It's a 2004 Kx250F..and the plug is a CR8EB. The rest i really don't know. The bike runs awesome. It's just it keeps dying after 20 minutes or so of riding...I was thinking maybe bad float? I don't know much about carbs but i was thinking that when i first start the bike the bowl on the carb is full...and while i ride it doesn't refill? and after it dies and sits for a few minutes it fills again? and starts back up and runs fine......I don't know if that makes sense or not so if you know a lot about carbs please help me out.-JB  
Pain is temporary, Glorys forever.

Stupid question... did you clean the fuel filter?  It's located behind the petcock on the tank (the on/off valve). These can get clogged and cause the very same problems you are experiencing.

Also - plan to check the valve clearances soon, if you haven't already.  A 250F really needs to have it's valves checked every 20 hours of runtime.  
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Here we go again!

When it comes to carbs I would get ahold of Skipper.  He really has the science of them down good.

As for your 04 bike.  The best upgrade you could get is procircuits water pump and radiator hoses.  That year bike was notorious of overheating which could be a part of you powerloss problem.  

Bill H. 2000 CR250R

actually bill a lot of times the electrical system can fail after the bike warms up. i talked to an electrician who use to race semi-pro and the shop aobut it and they both agree that a lot of times the electrical system fails after the bike warms up.  
______________________________
Ride 2 strokes, buy 2 strokes, save the 2 stroke.

1998 cr125
2002 cr80

how does that make sense? just trying to figure that out and i dont see the logic in that statement. ~pat  
PEACE GUYS ITS BEEN A BLAST!!!!! ~patrick

Elko - these bikes don't have electrical fuel filters, dude!  Get with the program here!

 
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Here we go again!

It does have a pro circuit water pump. And the fuel filter is fine..  
Pain is temporary, Glorys forever.

im just saying that because bill said he is ruling out electrical. but this guy i know is top of the line electrician and use to be a pretty damn good racer. probably better then everyone on here. and they said that if the electrical system is going that there is more chance that it will happen after the bike warms up. i dont know why, that just what they said. when i was fouling a bunch of plugs after i bought my bike that waht they said it might be.  
______________________________
Ride 2 strokes, buy 2 strokes, save the 2 stroke.

1998 cr125
2002 cr80

OK - a few more thoughts...

CHeck to make sure you don't have a pinched or clogged vent line coming from the bottom of the carb - that will cause the bike to do what it's doing.

I wouldn't rule out a faulty killl switch either - we saw one of those this week that would case a bike to run, then stop - then run...  
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Here we go again!

elko6:
actually bill a lot of times the electrical system can fail after the bike warms up. i talked to an electrician who use to race semi-pro and the shop aobut it and they both agree that a lot of times the electrical system fails after the bike warms up.

I am an electrician.  The only electical componants that really mess up under the amount of heat a dirt bike will provide are diodes/transistors, and mostly they will just slow down.  Thats why computers will slow down when they heat up too.  Heat expansion in a wire can cause some connectors to come loose, but nothing an a dirt bike would lose power because of that.  It could cause the engine to stop running, but thats not his problem.  

Bill H. 2000 CR250R

I could just unplug the killswitch to test that theory right?  
Pain is temporary, Glorys forever.

elko6:
im just saying that because bill said he is ruling out electrical. but this guy i know is top of the line electrician and use to be a pretty damn good racer. probably better then everyone on here. and they said that if the electrical system is going that there is more chance that it will happen after the bike warms up. i dont know why, that just what they said. when i was fouling a bunch of plugs after i bought my bike that waht they said it might be.

I know of the problem he is reffering to.  The cfi gets hot and fails to fire the ignition a few times bathing the spark plug with unspent fuel causing a wet foul.  

Bill H. 2000 CR250R

hmmmm. on most bikes you can but im not sure if you can do that on the newer bikes i'd assume so? ~pat  
PEACE GUYS ITS BEEN A BLAST!!!!! ~patrick