Top 20 2011 KTM 250 SXF Questions & Answers

.010" inlet hot .012" exhaust hot if water cooled if air cooled add .002" to the measurements

When you "give it gas" you are opening the throttle. At that point the fuel system is supposed to supply the engine with more fuel to maintain the air/fuel mixture. Check for anything that might be clogged like filters, hoses, fuel passages, etc. If it is still under warranty you could void your warranty if you work on it though in this case a warranty is meaningless if you have taken it in 6 times. I've seen models where you could replace everything and a week later it would refuse to run. Sometimes it's better to leave the thing at the junk yard and buy a new one but that doesn't happen often.

Sounds like a defective control box...if it is under warranty i would let them fix it right.

Thank you for contacting FixYa with your inquiry.
This is a tough one but I have had similar problems with other bikes usually an upgrade for a chip in the ignition systems computer or black box.
In this case it sounds like the stator winding's. When it's cool all is well in runs normal. When heat transfers to the stator (Basically an Electric Motor with Winding's around it's poles) it expands and the winding's could be separating and/or shorting out. You could test the leads with a good ohmmeter (meg ohms) after your runs and see if there is a different reading then from when it's cold.
http://cyclehuttktm.com/FicheFinderNew/FicheFinder.aspx see figure #3 3 77139004000 STATOR $184.99 $184.99


This is not a cheap part but it should be a warranty item as new as this bike is.
Hope this helps get you in the right direction,
Best regards,
TF

try ebay.com

if the bike starts after a short time it could be a blocked filter or a carby problem needle and seat or a stuck float,if not the bike might be over heating and siezing partialy,hard to say without more info.hopes this helps

Question edited for clarity. That sounds like it is just a bad connection somewhere or possibly a bad switch. Remove the battery leads and clean the lead contacts and battery posts with a wire brush. Smear with Vaseline and reconnect. Remove the starter leads and do the same. Then it could be the Starter Relay https://www.google.com/search?q=ktm+450+sx-f+starter+relay+location Or Starter Button https://www.google.com/search?q=ktm+450+sx-f+starter+button+replacement ..

That would be like riding a fixed wheel bike.Think about how you will stop and start. Only hydraulic fluid will leak. Bad idea!

personnaly I would replace cylinder with new OEM

All dirt bikes have a VIN. It is on the steering neck. https://www.google.com/search?q=vin+on+my+ktm+300 ..

Have you checked battery connections. Run switch in the correct position? Checked spark plug for debris? Just thinking out loud..

Drain oil. Use degreaser to clean area. Use JB Weld & allow to set up properly before adding oil.

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Hi, most likely your cdi unit or ignition coil needs replacing.

took me a min or two of WTF-ing to see pic and realize you meant a 2-stroke motorcycle..

try replace spark plugs

It's a bad seal of the head gasket. You need a new head gasket and to scrape every particle of debris from the cylinder head and cylinder surfaces that mate with the head gasket. Use the factory specified gasket sealing compound and do a clean job - no blobs or pools of the stuff. The head gasket should lay flat on the surface of the top of the cylinder, and you have to make this surface free of grit, leftover sealant and any other foreign matter before you put the head in place and torque it down. Start with the head bolts just finger tight and then go by the manufacturer's specs for the pattern and amount of torque to be applied. Usually it is recommended that you get to the specified torque amount in stages, going around several times and repeating the torque pattern until you get that maximum rated amount. This will prevent the seal from shifting or warping and should make the gasket seal perfectly. This is the old school method of doing this job. and I have never seen this fail to produce good results. Take your time, be clean, and you will have the results you want.

Check the clutch, adjust, clean, or replace

over full sump fuel getting into sump badly worn rings allowing excessive blow by

Worn out shift dogs.

Have you tried an emissions test? That can tell you a lot about how the combustion is doing, and what you would need to adjust at the carburetor. Have you checked the spark plugs?