Top 20 2010 KTM 250 SX Questions & Answers

I would first check the compresion to see if you do it will need a propper tester.

bikes are not meant to lay on their side they have a float which shuts off fuel in normal up right position

Take the engine apart and you will find out. Quite possibly will need new piston kit and a thorough cleaning and you'll be fine. If you're unlucky, main bearings, and cylinder coating repair.

Mervin, I'm not a motorcycle mechanic, but just knowing engines as I do, I would say drain the fuel tank and replace with new fuel and either a water remover additive or a more complete fuel treatment (Lucas makes some great products for that); pull the plug(s) and check them for any corrosion or buildup, replace if necessary; change the oil and filter; check the air cleaner; and check tensioning on any belts. I'd also suggest either replacing the battery straight away or just putting it on a charger for a while so you know it has a full charge when you go to start it - if you need to replace it, that will eventually become evident, but you should at least be able to get the engine started and see what else -if anything- needs doing.

The starter pinion attached to the kick pedal has an ratchet pin that engages in the engine shaft - the role of the pin is to allow the engine to turn freely once started. This pin is pressed on the shaft with a simple spring that in your case either broke or went out of position.
You will need to open that side of the transmission, access the starter mechanism and refit or replace the pin and its spring - it's a delicate job, work very carefully or you can do a lot of damage if you try to start the engine with the parts misplaced.

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?

Make sure the wires on the other side of the relay box are holding when you push the relay in.