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2003 klx 400 hard start when hot

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Hey everyone got a good one for you, When motor is hot, I have not been able to get it started again, I had to push it home today about three blocks not fun at all, this is the second time this has happened, I just got the bike a few weeks ago, I have changed plug and air filter the normal type stuff, starts great when its cold out runs great but when i stop it when it's warm it wont go again, It did not have this proble with the previous owner, where do i begin to look for problem's?

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sort of sounding like a ign. problem...

but we will need more info...

bike- klx 400?.. S or SR

any mods to it..

mileage?

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Assuming it cranks over but does not want to start, check the valve clearances.

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It's a s model with 5600 miles on it bone stock, It cranks over just fine acts like it's not getting any spark at all dosn't even try to fire at all, but if you let cool down over nite it will fire right up?

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When it is hot, pull the spark plug, confirm whether you are getting spark.

Or have a spare one ready, so you don't have to burn your fingers.

Would also check the valves

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you will need to do resistance checks with the bike cold and then again when it wont run.

at the stator/cdi plug check the resistance with a ohm meter between tyhe black and white wire and the blue and green wire.

you probably find one of them goes to "open" when hot.

it could just easily be a tank venting issue.

you should cofimr its a lack of spark issue before getting to in depth.

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so today after work I went to start it and nothing again, this time it acted like it wanted to a few times, backfired real bad out the exhaust. So after I check to if it has spark were do I go from there if it dosn't or the spark is erratic? I dont have a good manual so its hard for me to firgure this out, thanks for everyones help.

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Intermittent ignition problems are hard to trace and verify. Do the tests you can do: check valves, spark at the plug, resistance tests hot and cold, gas in the carb when it quits, simple stuff like that. If you get it running, take it for a long ride (with a follower truck to rescue you). Does it run fine for say 2 hr? Or does it crap out when it gets good and hot like 1/2 hr, then fail to restart? A manual will not help you much. Report your findings.

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Now it wont start at all for me, backfires a little bit here and there but that is it. So If i check for spark and there is very little or none at all where is the first place to look for a problem? thanks again

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K we have spark it started up and ran pretty good I let it run for about 10 minutes no problems, shut if off went to start again and nothing but a few little attempts. so I pulled the plug again still have spark, checked the fuel make sure no clogs or anything like that, ***? why wont it start back up just after a few minutes of running?

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K we have spark it started up and ran pretty good I let it run for about 10 minutes no problems, shut if off went to start again and nothing but a few little attempts. so I pulled the plug again still have spark, checked the fuel make sure no clogs or anything like that, ***? why wont it start back up just after a few minutes of running?

check your valves :)

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tsc - At some point you are going to have to get your hands dirty checking out the things that have been suggested. Then post again.

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Not a good find, I beleive the head gasket is blown, I discovered large amounts of water coming out the exhaust, and also in the oil, So i guess it's time to tear into and see what happened, im hoping the head is not cracked. thanks for all your help on all the problems I've had

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Water in the oil is not good. That can happen at the head gasket, base gasket or the Rt side cover gasket or the water pump. Water in the exhaust is harder to evaluate because condensation from combustion is normal. Is the cooling system loosing water? Bubbles in the coolant from leaky head gasket?

Water in the oil and non-start when hot does point to a head gasket or some kind of a compression problem.

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