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2012 kx250f seeming off?

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Tl;dr bought a bike I thought was mint and it quickly went to shit

Ok so I bought this bike 3 weeks ago for 5 grand it was raced but looked in real good shape

when the guy started the bike it only took 2 kicks without the cold start knob and me coming off a ttr230 w/ electric start could start it in 4

well fast forward to now it needs wide open throttle to even come close to starting cold or hot and it will stall in under 10 seconds if I'm not giving it any throttle in neutral or with the clutch pulled in

Also I was running regular 85 octane gas with octane booster and now i put some supreme 91 in it too

today I changed the oil oil filter and cleaned the air filter seeing if that would help but no luck so I'm stuck

I'm wondering if it is something I overlooked or if I got ripped off or bought a piece of shit bike

Edited by Sneaking snacks

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Possibly dirty injectors. Maybe also do a compression check. One TPS could be bad. These are just a few things that could give you those symptoms. The bike is pretty bulletproof. Any idea on hours?

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I will answer your question, but the key information would be what, if anything, did you do to the bike between the time it ran perfectly and now?  Anything but different gas?  If not, suspect the gas first.

 

Compression should be around 62-103 psi with a fully warm bike with WOT and 5 kicks.  90 something seems like a good target.  

 

The TPS can be an issue if it was rebuilt.  They need to be dialed in.  I will post a how-to thread in a little while.  Even the slightest movement of that thing can cause a good bike to go to hell.  The gas you run should be pump premium.  The plug should be in good shape and properly torqued.  A loose plug = compression problems and shitty running.  Air filter needs to be clean (check!)  Boots from throttle to head and from throttle to air box need to be tight.  Head pipe has to be sealed against the head and at the mid pipe connection.  The idle has to be adjusted correctly, too.  Turn the high idle knob counterclockwise to increase idle speed.

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Thanks for the info dragon I will try adjusting the idle knob tomorrow should I do it while it's running and will that affect performance whin I'm driving it

Also what do you mean by the plug

Edited by Sneaking snacks

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Thanks for the info dragon I will try adjusting the idle knob tomorrow should I do it while it's running and will that affect performance whin I'm driving it

Also what do you mean by the plug

 

I meant the spark plug.  Yes, you should adjust the idle knob when you are running.  It takes a few clicks to make a difference.  You should pull the high-idle knob out to start, and let it warm up good before you push it in.  You don't want the idle too high when riding, of course, but if it's really low the bike can stall.  I think if I were in your position I would just keep putting good premium pump gas in it and run it.  If you have more issues, reply to me so I know you are looking for more help.  Others here will be very helpful, too.  Enjoy the ride tomorrow!  You have a great bike.

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It's a 2012 efi would it still have a spark plug

 

Yes, it has a spark plug.  Hard to find it, but it's there  ;).  If you do decide to pull the spark plug out for any reason, pull the plastics on the front and unbolt the tank at the top.  You can move the tank around a bit without disconnecting the fuel line and power line to the fuel pump.  This will help you get at the plug and the valve cover so you can check your valve clearances.  Also, before you pull that plug, clean the area around the plug thoroughly with some carb cleaner or WD-40.  Whatever you spray into the plug cavity will come out of a weep hole on the right of the cylinder.  Keep in touch and definitely get a full service manual for your bike, if you don't have one.  It is absolutely necessary.  

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Any idea where I can get the service (I already have owners) manual? eBay the best choice, or is there something cheaper?

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I got mine on eBay for £9 odd and it's a pretty comprehensive guide to doing anything on the bike!

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