Bike Won't Stay Running KX250

Joined
Feb 2, 2007
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#1
My good friend has a 1996 KX250. It was running great last weekend. This weekend, it won't stay running. Changed the plug and checked the spark. If we lay the pulg on top of the head the spark is VERY weak. If we hold it off the head about 1/4 inch, spark is VERY good. :coocoo: It will fire off but stall almost immediately when you give it gas. Carb is clean and so is the air filter. Any ideas before we start throwing parts at this thing??? Thanks.
 
Joined
Jul 18, 2007
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#2
take a look at the reeds... i kinda doubt they went bad over the week though.

when you say "It will fire off " do you mean it idles but dies when you give it gas?
 
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Feb 2, 2007
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#3
It really doesn't want to even idle anymore. It did idle a little at first but it definately cuts out when you give it gas. I'm kinda leaning towards the weak spark but I'll tell him to check the reeds. He's only had the bike 2 months at the most and hasn't done any mods himself to it. I'm not sure if the guy before him changed them.
 
Joined
Oct 31, 2005
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#4
Have you changed the plug for a new one to see if the problem goes away? When you hold the plug 1/4" away from the head you are probably seeing a spark jumping from the outside of the plug to the head, not between the contacts, right?

The spark should be a nice blue spark and consistant in relation to the piston movement, the first port of call would be the plug. If the spark is still weak, change the HT lead, then HT coil. Past this point you will be looking at the coils on the stator, CDI etc...
 
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Sep 12, 2007
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#5
try using a actual spark tester for checking spark it will have a built in resister that acts as compression (its easier for it to spark w/ no compression) this will give you a better idea as if you have weak spark or not if you have a manual you should be able to test the coil by using an ohmmeter it should have a spec for the value of resistants the coil. if you have a magneto puller you could also look at the stator to make sure no dirt has scuffed it up and that the pickup is visually ok (do not start it w/ side cover off)
 
Joined
May 5, 2007
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#6
I know this might sound kinda stupid but have you let it idle for about a minute then given it gas?My bike has to idle for about 20 seconds before you can give it gas without it dying.And maybe te gas has settled if it can do that, like the oil has settled to the botom of the tank.Im not really sure if mixed gas can do that though but ive heard people say it can.
 
Joined
Feb 26, 2007
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#7
I have a solution....buy a yamaha. Check the reeds but while you do that you can clean the carb too. and make sure nothing is stuck
 
Joined
Feb 2, 2007
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#8
I do have a Yamaha!! :) Anyways, thank you all for the tips. We took the carb back off and looked to find ORIGINAL reeds. The previous owner put the aftermarket pipe on it and some other stuff but left the reeds alone. So we went down to the shop and got some new reeds and for haha's I made him buy another plug. "Ya never know", I said. Slapped it back together...checked the spark and it was much better! I mean, it looked like a spark instead of a flicker. Quality control must of fell asleep for 5 minutes because the other new plug did almost nothing. Low and behold, it's running again. Here's the kicker. When we went riding last weekend, instead of admitting he was broke and bumming some gas off me he used some out of his shed with some cheap oil in it that was at least a year old.. 87 oct. to boot! :yell: Had he told me that to begin with we could of avoided alot of wasted time and effort. Thanks again guys.
 
Joined
Sep 13, 2007
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#9
read my post in the main page very same problem i have here

stacked ball bearing on crankshaft, Very strange but true :bang: