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Dirt bike dies in 1 min

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When I satrt my bike it runs for a minute or two then just. When I take off the spark plug theirs fuel on it. Do I need a carb rebuild or adjust the carb

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what mix are you running?  I have a '99 RM250 & the book says 32:1 but I have always run 40:1 using ethanol free 93 octane

 

what's the air screw setting?  stock should be all the way in then back it out 2 and 1/4 turns

 

how do the reeds look?  if they're cracked, that could cause it.  they also can look fine & be worn out causing the mixture not to properly atomize, reeds are pretty cheap...

 

which spark plug are you running?  I always had good luck with the NGK BR8EG, although the book says to run a much more expensive plug

 

have you mic'd the cylinder?  just because it has a new piston & rings, does not mean the stock bore hasn't worn out, might be time to resleeve or replate...i'd try all other options 1st though

 

& 15 hours if frequently holding the throttle pinned actually means that top end is prolly ready for new rings if not a piston too, I think the book says 10 hours if you "race" lol

 

 

edit:

 

definitely do what's listed above, they're smarter than me.  The tank breather can get plugged & cause it to die like that, but I would not think you'd have fuel on the plug if it was starved for fuel...  still worth checking.  and good question, when it dies, immediately pull the plug & check to see if it has spark, could be electrical i guess, if it is, I may not be the best person to help you, i suck at electrical lol

Edited by chevyrulz
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Is the plug really wet?  Could be running rich and fouling the plug.  Open up the air idle screw and see if you can get a good idle, if it's turn out too much in order to set idle, then you are probably running too big of a pilot jet.

 

Get a new spark plug and see if it does the same thing.  You could just have a fouled spark plug.

Edited by Honda_Power

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Did you make a recent jetting change?   Was there a recent large temperature increase in your area?  Sometimes a bike will run super well with really rich jetting when cold, then run like a turd once it's warmed up...

 

As someone mentioned this is typical of a stator problem.   Sure, you're seeing spark when you pull the plug and look, but by then the bike may have cooled enough for the intermittent stator problem to have fixed itself.....

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The bike was runing perfect 2 weeks ago didn't touch it since this week when I was going to go around block and died after runing for 2 min

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Could be as basic as the carb needs cleaning. Is it dying when you reach a certain RPM range, or does it make no difference whether wide open or near idle? If so you may need a rejet. I would take carb apart and clean it well, including inside of jets, clean air filter and make sure no blockage, check reeds for wear, chips, gap. 

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That would probably put you lean if anything, I would imagine the pressure inside the boot and the flow into combustion chamber would create a vacuum and pull air in through the crack. Or the opposite, it could be leaking. Is there any fuel coming from the crack? You could try putting a light sprinkling of baby powder around the crack and have someone start it up, see if it there is a visible air leak. How big a crack are we talking? 

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Either way, you could test whether that's the problem by sealing up the boot with some silicone (like what you would use in a caulk gun), seal from the outside so as not to cause any harm, let it set well, then give it a shot. If it does fix the problem, replace the boot anyway, as this is not a long term solution, just a means to test. 

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Thanks u guys I found my problem my air screw was turned to high and I had a vacuum leak on the rubber boot

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