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kx250f starting issues.

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hey guys I got 6 hrs on my rebuild and its been running like a champ...but lately its been a pain to start. my valve clearances are within spec. their on the loose side of the spec but they get tighter as things wear. I went and adjusted the mixture and when it fires it idles flawlessly and has perfect throttle response with virtually no popping on decel. but it takes a lot of kicks even when warm and is back  firing about every 10 0r 15 kicks. the hot start plunger threads are gone so im sure its got a small air leak from that( new cable on the way) do ya think that's the issue? everything else seems to be where it should be and its only got 6 hrs on a full rebuild. any help would be greatly appreciated.

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both. ive been messing with it and have got it to start easier, but sometimes it still takes a good few kicks. I think its prob the hot start leakin air. it also seems to like to kick start better with out the choke it seems but idk if that is related.

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The hot-start cable threads shouldn't make a difference.  They don't seal anything except dirt and water.  The plunger itself has a one-way o-ring that can wear out and lead to a lean condition.  That could impact your cold starting.  The rule of thumb is, the bike should not want to start cold without the choke.  Also, popping on decel could mean a leaky header to head connection, which is easy to fix but definitely impacts starting, even with an FI bike.  I would replace the plunger with the assembly and start from there.  Also, if you are unsure about whether you reassembled the exhaust correctly, you might want to order a couple of the gaskets that go between the head pipe and head.  They are cheap and they must be new with every re-install.  Actually, we just got one in a Tusk top end kit that was much better than the copper crush washer.  Not sure if you can buy the Tusk version separately, but they do work well.  The way to tell if you have a head-pipe leak is if it turns cherry red when idling.  It does this because unspent fuel is combusting in the head-pipe due to air infiltration.  That's what decel popping is caused by, too.  When you shut off the air to the motor (by closing the throttle), there is more unspent fuel that gets to the super-heated head pipe, mixes with air, and "pop!"  Keep us posted on your progress.

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both. ive been messing with it and have got it to start easier, but sometimes it still takes a good few kicks. I think its prob the hot start leakin air. it also seems to like to kick start better with out the choke it seems but idk if that is related.

Check around the air boots and make sure there are no leaks there.

Grab a propane torch, let gas out of the torch. While the bike is running spray it around the boots connecting to the carb and to the intake on the engine

If theres a leak there will be a change in idle

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My kx250f won't start with the kick but if I roll start it it goes without a problem. And once I have it going it runs fine. I can kick it over 30 times and it won't even hardly fire but when I roll start it it instantly starts and idles fine. Starts decently with the kick after also.

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My kx250f won't start with the kick but if I roll start it it goes without a problem. And once I have it going it runs fine. I can kick it over 30 times and it won't even hardly fire but when I roll start it it instantly starts and idles fine. Starts decently with the kick after also.

 

Common problem when inlet valves are tight

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Get guys I have a 2010 kx250f I was ridding around the yard last week and I shut it off, when I went to fire it back up it wouldn't start I figured out it had no spark! And suggestion? Or has anyone else had this problem anything would help thanks

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What was the outcome of your bike issue.. Im following. My hot start is stripped out. I also got a new one coming.. Im thinking it making it to lean... Could i be right. Any info would help... Thx

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