7 Common KTM 250 SX-F Problems (Explained)

The KTM 250 SX-F is one of the most powerful and reliable motocross bikes in the 250cc, single-cylinder four-stroke class.

Though widely considered one of the easiest and most fun motocross bikes to ride, no machine is perfect.

This article covers the most common problems with the KTM 250 SX-F.

1. Clogged Fuel Filter

KTM 250 SX-F owners report incidents of engine bogging and backfiring, often the result of a clogged fuel filter restricting fuel flow.

“A week ago, I bought a 2021 KTM 250 SX-F. The next day, when I got to the track and opened it up on the track, it would bog out and die. I was at the track for an hour, constantly trying to get the bike to work properly, but I didn’t even get one full lap in.

I took the bike to my dealership, and they found that there was grease in the main jet, so they cleaned it out…. and the bike still won’t run.

It idles fine in neutral and sounds as crisp as a new bike can, but once I get on the gas and the rear wheel starts spinning in the dirt/sand, the bike either bogs out and dies or the bike backfires like crazy and barely moves when in gear.” –thumpertalk.com

To fix a clogged fuel filter on the KTM 250 SX-F:

• Remove the seat and the fuel tank, and then disconnect the fuel line and drain the fuel.
• Remove the fuel pump and the filter and check for clogs/damage.
• Replace the filter as needed, reinstalling everything in the reverse order of how you took it apart.

2. Leaking Gas Cap

KTM 250 SX-F riders also complain about the bike’s gas cap developing fuel leaks, which can range in severity.

“The only problem I’ve had is the gas tank leaking. KTM gave me two caps that both leaked as well. They just gave me a new tank w/ cap and graphics last weekend. –thumpertalk.com

“Try finding a gas cap that doesn’t leak. Other than that, my sister-in-law hasn’t had any problems.” –thumpertalk.com

• To fix a leaking gas cap on the KTM 250 SX-F:
• Check and replace the rubber O-ring that seals the tank.
• Adjust or replace the cap’s locking mechanism that secures the cap.
• Align the cap correctly with the tank opening.
• If none of these solutions work, replace the gas cap.

3. Faulty Cam Chain Tensioner

More than a few KTM 250 SX-F riders report strange ticking noises and running problems as a result of a faulty cam chain tensioner.

“I have an Sxf 250 2015, and the problem is that it makes a ticking noise when hot. I think that valve clearance should be ok. I haven’t checked it yet because I’m not sure about opening the valve cover. But I think that the cam chain should be loose, and as I have been reading, KTMs have a bad cam chain tensioner.” –ktmforums.com

“… sadly, this sounds like a common issue with these. The cam chain jumps a tooth, and the timing is out as the chain, for a short moment, loses its tension. These have a hydraulic chain tensioner that, in principle, should work well. But for some reason, it fails after some time (often when dropping down to a lower gear or going from full noise to idle quickly). But only by dismantling the top end and side cover can you find out. I do not know the reason for the failure (and as we only race 2strokers, I have not personally seen the issue). I have heard of owners who replace this tensioner with a manual/rigid one.” –ktmforums.com

To fix a faulty cam chain tensioner on the KTM 250 SX-F:

• Remove the stator cover.
• Reset the tensioner to the fully retracted position.
• Reinstall the tensioner and align it with the cam chain.
• Release the tensioner with a screwdriver.
• If the chain goes out of tension again, the tensioner is faulty and needs to be replaced.

Related: 7 Common KTM 350 SX-F Problems (Explained)

4. Overheating at Start-Up

Other KTM SX-F riders report chronic problems with overheating, especially when they’re trying to start their bike.

“I have owned a 07 KTM SXF 250 for about 3 months. I have only been riding for just over a year and take part in mainly practice track days, and I compete in the local hare and hounds enduro championship.

The first problem/issue is that my bike seems to overheat quite rapidly compared to other 4-stroke bikes. The rad is filled with Sikoline engine Eskimo coolant. However, it seems to steam out of the overflow in no time at all. My second problem/issue is that when the bike has been running for a while, the engine gets hot, and I stall/fall off (usually the falling off), and the engine cuts out, I have real difficulties in starting the bike again. It doesn’t want to kick over I use the hot start lever, and nothing happens. I end up having to push it to the side to cool for a couple of minutes, but this ain’t no good when I’m trying to race! Is there a technique for getting these things started, or is it more of a serious thing?” –ktmownersforum.com

To fix overheating issues on the KTM 250 SX-F:

• Inspect and fix the coolant system, the thermostat, the carburetor tuning, the exhaust leak, and the air filter as needed.

5. Hard to Kick Start When Warm

Some KTM 250 SX-F owners report the bike is hard to kick start, especially when warm. While newer year models have electric start features, most of the 250 SXF year models don’t.

“I hate getting this new bike started when it’s warmed up. Do you have any ideas on how to make her kickover easier? I kick and kick and get nothing. It takes about 3 mins to get it started every time once it is warm, and it’s tiring. Any help?” –supermotojunkie.com

If your KTM 250 SX-F is hard to kick start when warm:

• Try using the manual hot start lever mounted on the cover of the clutch master cylinder. This lever reduces the amount of fuel in the combustion chamber and makes it easier to start the bike when hot.
• Avoid using any throttle when kicking, as this floods the engine with fuel.
• Inspect and adjust the jetting and the valve clearance, as these are the two most common reasons why KTM 250 SX-F is hard to start when warm.

6. Throttle Drag Issues

Riders sometimes report throttle blip problems, where the bike’s throttle gets bogged down from a rich air: fuel mixture. This can affect the bike’s throttle response, eventually causing starting problems.

“I just bought a 2018 KTM 250 SX-F, and when I try to start it, it just cranks, and cranks, and cranks, but no start. If I hook it up to a jump box, it starts right away.

9/10 if I apply any throttle or go to blip the throttle after starting, the bike just dies. I got the bike to run & idle for about 3 minutes, and then I went to hop on, put it in gear, went to blip the throttle & the bike just died. I started it again with the jump box, and this time, SLOWLY rolled onto the throttle and got it rolling. I went down the street & the bike felt like it maybe had 30% of its power. I stopped at the end of the street to turn around, went to blip throttle again to roll off the clutch & bike died again.

The bike won’t start with the electric start if it’s not hooked up to a jump box. But I don’t see how that could be affecting the bike dying when the throttle is applied & the bike only has 30% of its power.” –Reddit.com

To fix throttle drag issues on the KTM 250 SX-F:

• Inspect and adjust the throttle position sensor (TPS) as needed.
• Check your fuel injector, the fuel filter, and the jetting.
• The KTM 250 SX-F has a cold start knob located on the bottom of the throttle body and helps to enrich the fuel mixture when the bike is cold. Make sure it’s turned off if it’s hot out, as it can cause the bike to run rich and bog down its thorttle.

7. Clutch Won’t Engage

Finally, riders sometimes report the clutch of their KTM 250 SX-F periodically fails to engage. In other situations, the clutch engages the engine, but nothing happens.

“2017 KTM 250SX-F. I recently purchased the bike 2nd hand and got to ride it for the first time on Sunday last week. The bike was sitting for a few months prior to me purchasing it. The clutch lever feels like it has good pressure and isn’t spongey at all; it feels like it should be to the left hand.”

Once the bike is running and I aim to get going, shifting into 1st gear causes the bike to stall even with the clutch lever fully engaged down to the bar… The clutch fully engages, but nothing is happening!” –Reddit.com

To fix a clutch that won’t engage on the KTM 250 SX-F:

• Inspect the hydraulic system, bleeding it as needed.
• Check and replace the clutch plates or springs as needed.
• Inspect and adjust the clutch lever or cable as needed.
• Check the shift forks by removing the transmission cover and inspecting them for any damage or misalignment.
• Inspect the gears by removing the transmission cover and examining them for any damage or wear.

What Are the Pros and Cons of the KTM 250 SX-F

Pros:

• Powerful and reliable engine
• Effective suspension
• Easy handling and comfortable riding position
• Excellent stopping power.
• Lightweight; easy and fun to ride.

Cons:

• Clutch Won’t Engage
• Throttle Drag Issues
• Hard to Kick Start When Warm
• Overheating at Start-Up
• Faulty Cam Chain Tensioner
• Leaking Gas Cap
• Clogged Fuel Filter

What Are Some Alternative Models?

What’s the Resale Value of a KTM 250 SX-F?

Sources:

250 Sx-F For Sale – Ktm Motorcycles – Cycle Trader

KTM 250 SX-F motorcycles for sale – MotoHunt