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Old 03-20-2017, 09:49 AM
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Default My 2009 kx250f will bump start and not kick start.

     

Hi everyone. So i currently have a 2009 kx250f and This last week i have tried to ride it but it only starts when i bump start it ( when first starting it). When riding it still has plenty of power and when its warmed up i CAN hot start it with one or two kicks . The past few days i have rebuilt and cleaned the carb and i noticed that my main jet on the bike was 175 and the new replacements came with two. i dont quite remember the numbers but i think it was 182 and 186. And i put the one closer to the 175 number in. I have been messing with the fuel jet screw to get it to run better but i cant seem to make it run as good as i would want it. I have also noticed that i am not certain if the the two little air holes(air mixture intake jet) are lining up in the air filter attachment side of the carb to the two hole at the bottom of the air filter tube. Because while riding i can can slightly turn the carb and make my bike run smoothly and not bogg when accelerating. Should i think about rebuilding top end?(because its a sign that i cant kick start it at first) p.s: timing is good/ new plug / correct oil / valve spacing is good ( not 100% sure about my carb jetting).
Any advice would be much appreciated.
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Old 03-20-2017, 10:27 AM
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If all the jets in the carb are clean and you haven't had any issues prior to this I would check and make sure your accelerator pump it working. If not you'll be having issues like that.
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Old 03-20-2017, 10:36 AM
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I replaced the accelerator pump diaphragm because the previous one was all cracked. maybe little piece of the bad diaphragm clogged one of the tiny holes and i didn't notice it. But i think when i turn the carburetor it caused a smaller gas to air ratio and basically gives it more gas than it needs. Could there be anything else as well and thank you for the help.

Last edited by skykx250f; 03-20-2017 at 11:44 AM.
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Old 03-20-2017, 02:36 PM
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Only starting cold by bump starting indicates bad valves. Just because the gap is good does not mean the valves are sealing.

Paw Paw
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Old 03-20-2017, 06:01 PM
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okay thank so no matter what im taking the head off. If theirs anything else that could be the cause i would love to hear it.I am trying to rule out every possible issue.
thank you for the advice PawPaw!!!
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Old 03-21-2017, 06:03 PM
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I agree, sounds like valves to me too.
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Old 03-22-2017, 11:40 AM
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thanks everyone!!
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Old 03-24-2017, 01:54 PM
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I checked the valves and they are leaking very slowly.
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Old 03-24-2017, 02:58 PM
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Time for a valve job!

Paw Paw
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Old 03-25-2017, 10:39 AM
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I'm having a hard time finding anything close to me that will do a valve job. Any advice on where to go. Or am I going to have to send the head off somewhere. I'm located in Nashville.
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Old 03-25-2017, 08:11 PM
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I would send it to Fast Heads. They do very good work. The other choice would be Merge Racing. More than likely you will need new seats( if a cut will not clean them up), new valves, keepers and valve shims. In most cases they can do the new shims right on the bench so it's ready to bolt on and go.

Paw Paw
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Old 03-30-2017, 10:33 AM
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I found a headworks dirtbike shop near me. They came back to me a few days later saying I need a new head. Because apparently the previous owner got dirt in the engine and wore the valve seat past the point of fixing it. They want 1200$ To replace it . I'm not going to spend that much yet but any advice on what to do. I'm also worried they are lying to get more money. Because my personal inspection didn't seem to be that bad. Any help on what to do? I know there are 900$ used heads out there.
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Old 03-30-2017, 11:04 AM
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Quote:
Originally Posted by skykx250f View Post
I found a headworks dirtbike shop near me. They came back to me a few days later saying I need a new head. Because apparently the previous owner got dirt in the engine and wore the valve seat past the point of fixing it. They want 1200$ To replace it . I'm not going to spend that much yet but any advice on what to do. I'm also worried they are lying to get more money. Because my personal inspection didn't seem to be that bad. Any help on what to do? I know there are 900$ used heads out there.
As a 2 stroke owner, I read this and I cringe. I know it can be avoided by proper maintenance, but damn... I can rebuild the whole engine on my CR for less than that.
If you want some good advice, I think the best bet is going to be to post some detailed pictures so the guys with more knowledge can help you diagnose the extent of the damage and give you a good estimate of the cost to rebuild or replace the head. It SHOULD be possible to replace the valve seats and install new valves. The shop MIGHT be trying to do what is easiest and most lucrative for them in just installing a new head. I suggest getting a better idea of exactly what work the current head needs before getting a used head that may have its own issues.
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Old 03-30-2017, 01:50 PM
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FYI: Fast heads can replace the valve seats and them cut them as needed. You do not need a new head just for new seats. You should be able to get the new seats, valves and springs put in you head and will under the price they gave you. Check them out!

Paw Paw
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