2021 KTM 250/350SX-F Top 5 Mods And Top 5 Maintenance Tips

We have seen some quality time over the last few months with the 2021 KTM 250/350SX-F and have come up what we think are the best as well as the most relatively inexpensive mods to each one of these machines. Both machines respond well to these mods and while we were at it, we put together our top 5 maintenance items that we have felt our test bikes needed. Here are the details, in no particular order.

1. KTM 250SX Air Filter Cage: This is the cheapest and easiest way to get more throttle response out of your KTM 250SX-F/350SX-F. You will notice better throttle response through the low to mid RPM range by simply going to a 250 SX two stroke cage with no backfire screen. Here is the part number you will need. P/N 5040601600

2. FMF 4.1 Full Muffler System: To me, FMF makes the best muffler system for the KTM 250/350/450 SX-F. There are some other companies that have other bikes dialed in more, but on the KTM, FMF has got it down. You will get more low to mid RPM response as well as more mid range pulling power. Top end is increased plus the over-rev is as good as stock. It is one of the few times that I was impressed because it was actually better than stock in almost all areas. The downside is that you must keep up on muffler packing (every 10-12 engine hours) because the FMF will blow out and that could damage your expensive titanium can. Did I mention that you will lose almost two pounds with the titanium 4.1 system? If you slap on spring forks on your KTM, you will be gaining almost three pounds. You can get most of that weight gain back down with a 4.1 Titanium FMF Muffler system.

3. Pro Taper Handlebars: The stock Neken handlebar is too stiff and doesn't offer too much comfort. Throw them in the trash. Get yourself a set of Pro Taper bars and make your arms and hands happy again. The Pro Taper SX Race bar worked well for riders from 5’8 to 6’1. The SX Race bend comes in a crossbar or crossbar-less style and is 800mm width, 87mm height, 54.5 rise, and 54mm sweep. If you’re looking for a better “stand up feel” from your KTM look for handlebar close to this measurement. If you do like the stock bar try the Pro Taper Husqvarna Stock bend with 5mm bar mount risers (Ride Engineering sells these).  

4. Throttle Tube: There are a couple you can choose from here… If you’re looking for an aluminum throttle tube that is expensive, but helps the feel of your throttle, I recommend the ZRT throttle. This throttle tube makes the pull have almost zero drag and is a tough SOB. There is some set up/prep time to this throttle (cutting the right side of the handlebars), but it can help the pull over the long haul. If you’re more the plastic style tube type of rider, look at the Motion Pro Titan tube as it’s tough for a plastic tube and doesn’t have as much drag as the stock lock on style ODI grip/tube that comes on the stock KTM’s. The stock plastic throttle has a lot of friction and gets tough to turn too quickly.

5. Ride Engineering One Piece Bar Mount: The Ride Engineering One Piece Oversize Bar Mount has a one-piece top that is designed to resist bending much better than the stock bar mount. Precision machined from aircraft quality aluminum, there is also a 6mm difference between the forward and back mounting positions. Ride Engineering also machines their own stainless steel posts that prevent over tightening, unlike some other competing brands that DO NOT use quality posts. This bar mount has saved my son and I a couple times when we are out doing motor. He seems to crash a lot in corners and the stock mount on the KTM 250 SX-F just twists and bends easily.

Extras: 

Rear Axle/Axle Blocks: Going to a Works Connection Elite axle block kit or Ride Engineering axle block kit will get rid of the fixed left axle block on the stock KTM’s axle. This will help the rear end to move more freely under throttle and improve the shock’s comfort on acceleration chop. Both are great, but you will have to decide if you want a complete axle/axle block kit like Ride Engineering’s  or just the blocks themselves like WC’s.

Rear Brake Pedal Spring: Purchase a Honda CRF450R rear brake pedal spring with the rubber around the spring. The KTM rear brake pedal spring vibrates and will break every 4-5 engine hours. Orrrrrrrrr. Get a Fasst Co rear brake return spring and be done with it! Fasst Co’s rear brake return spring offers tunable pedal resistance and a more controllable feel by placing the spring in compression instead of tension, minimizing the "on-off" feel of most rear brakes.

Top 5 Maintenance Items:

1. Fuel Filters: If you’re a KTM owner, do yourself a favor and put a couple of these in your toolbox just in case. Fuel filters can get clogged on all KTM’s and this can cause damage to your fuel pump or possibly not allow your bike to start properly.

2. Throttle Cables: If there is one thing that DOES NOT last on KTM’s it is the throttle cables. Every 15-20 hours I will have to replace the throttle cables to ensure that my throttle doesn’t feel hard or sticky when twisting. Originally I thought my throttle tube was dirty or maybe the right side of the handlebar had dirt on it, but I found out through a couple KTM mechanics, that the throttle cables simply wear out. You can’t lube them or clean them out as it will only make the throttle feel better for a short amount of time.  

3. Check All Spokes: KTM spokes always come loose near the rim lock so make sure you pay attention to all the spokes after every ride. If you don’t check them constantly you will lose or break a couple. 

4. Check Engine Mounts/Swingarm Pivot Bolt: Always check the torx bolts that hold the top engine hangers on the bike. After break in, these will loosen up a bunch, so you might need some blue Loctite on the threads. After you do this, please continue to check these as they still back out from time to time. The torque spec on these bolts are important to the ride attitude of these KTM’s. Also the KTM’s come with frame guards and that means you will not know (until it’s too late) when your swingarm pivot bolt backs out. Take off your frame guard and check pivot bolt regularly. While you’re at it, get the Acerbis frame guards as they last longer and have better grip than the stock ones.

5A: FI Indicator Light: The little FI indicator light bulb will fall out of the rubber casing as soon as you get past 10 hours. The best thing to do is put a little silicone inside the rubber casing, so the light bulb as well as the wire doesn’t flop around.

5B. *KTM 450 SX-F Only* Clutch Rubbers/Cushions: Over time (around 25-30 hours) The stock clutch rubbers could eventually crack and could cause your KTM’s clutch to slip. You might think that this is caused form the clutch plates itself, but if you pull your clutch apart you may see your fibers/steels are still good but these rubbers are cracked. Even if the rubbers crack, they can’t hurt anything as they are locked in place within the pressure plate. If you’re looking for longer lasting clutch rubbers that have a tighter tolerance you can purchase the Rekluse clutch rubbers for your stock clutch system and these have proven to last longer than the stock ones. 

2020 KTM 250 SX-F First Impression

Coming off the heels of our Husqvarna test last week, KTM came in this week and delivered our  2020 250 SX-F for us to shake down at the infamous Glen Helen Raceway. Glen Helen is one of the most used motocross facilities in California for most manufacturers to test their production machines before they arrive to dealerships. I managed to gather up 10 important things about the 2020 KTM 250 SX-F that I feel would benefit a possible future consumer and here they are. 

Engine Feeling: The KTM 250 SX-F is fast! It doesn't feel fast on low rpm, but is it’s so easy to roll on the throttle early in corners that it makes you a better rider without you even realizing. The 2020 KTM 250 SX-F has more bottom end power than the FC250, but both bikes are similar from mid to top end. The 250 SX-F top end is so impressive because it can rev out incredibly well in third gear and will surprise you on how far you can let this machine eat. The controlled engine character of the KTM 250 SX-F doesn't have the excitement of the YZ250F, but to me I can appreciate this controlled character as the rear of the KTM feels more connected than the YZ250F under throttle. You will not be able to use third gear in corners on the KTM like you can with the YZ250F, but having a second gear as long as the 250 SX-F doesn't make me really want to use third gear because second gear is so useable. If you are a third gear type of rider through corners the KTM does have a decent amount of recovery time, but going to a 14/52 gearing ratio (14/51 is stock) will help your cause even more. 

Suspension: The new 2020 WP XACT settings are firmer than the Husqvarna, but to me that is a good thing. The standard air pressure on the AER fork is 10.3 bars, but we ended up with a 10.6 bar base setting for both riders (170 and 185 pounds). The added air helped the fork hold up on de-cel yet still had a decent amount of comfort on the bigger braking bumps that Glen Helen provided. The WP KTM 250 SX-F shock has more damping feel than that of the FC250 on the end of its stroke, but doesn't have the comfort on acceleration bumps like the FC250 does. We stiffened up the low speed compression a couple clicks and that helped prevent the KTM from squatting too much under a heavy throttle hand. If you still feel like it’s soft at the end of the stroke on jump landings or g-outs try going in a quarter turn in on the high speed compression. Overall, I don’t think the 2020 WP suspension spec is that much better than the 2019 setting, but it was comfortable enough for me to push it hard around Glen Helen when the track got rough in the afternoon. Basically I wasn't dreading my time there in the afternoon and that to me is a win.   

Chassis: The KTM 250 SX-F feels light through corners and lacks a little front end traction once you add some air to the fork. The positivity of the front tire on lean angle will decrease when going up in air pressure on the AER fork, but this is only felt on corner exit. Initial lean and mid corner the KTM gives the rider a lot of confidence and doesn't require a lot of input by the rider to make an inside line. Straight line stability is also predictable as the KTM will react the same way every lap when hitting bumps at speed. The steel frame has a very connected/positive feel around the track. 

Transmission: We did have an odd feeling when shifting from second to third, under load, on the KTM. When coming out of a corner, under throttle, it was very hard to find third gear. I had to  let off the throttle and pull the clutch all the way in to make the shift. This was odd because our FC250 had zero trouble with shifting when we tested it last week. The Pankl transmissions are usually the best in the business, so having this issue could be just do to not having enough break in time on a new bike. Our KTM 250 SX-F test bike had under two engine hours on it, so maybe it wasn’t fully broken in, but we wanted to mention this. We will get back to you once we get over the 5-6 hour mark to see if this improves.  

Engine Braking: We mentioned in our FC250 test that the Husqvarna had a lot of second gear engine braking. With the KTM 250 SX-F this wasn't as apparent, which makes this transmission talk even more interesting. The KTM has a very free feeling engine character in both maps and this makes the whole bike feel very playful. 

Engine Maps: On the KTM 250 SX-F, Map 2 was a great all around map for both testers we used. Map 2 pulls strong through the mid range and gave us more “meat” feeling up the hills. Map 2 didn’t come on stronger than map 1, but gave the KTM more rpm response and mid range recovery time, while pulling harder up top. Map 1 was a little stronger off bottom end, but was too short for our testers taste. The TC button simply doesn't get enough play with test riders, but the TC button does work well for conditions that are slick, hard pack, and/or slippery. Find the preferred map you like to ride in and use the “TC” button when the track turns for the worse. I tried Map 2 with the TC in the afternoon and it does actually help the rear of the bike stay straighter upon accelerating. 

Rider Triangle: Gone are the days where the KTM feels foreign or weird when coning off Japanese machines. The cockpit fits a wide range of riders and never feels too cramped even with the low bar bend (unless you’re 6’2 and up). I do however despise the stiff natured stock Neken handlebar on slap down landings or on square edge. To get less vibration and more flex, get yourself a Pro Taper handlebar ASAP. If you like the stock bend, order yourself a Husqvarna stock bend and you will be in the spec range of the stock Neken handlebar. The KTM seat is also much friendlier than the Husqvarna seat! Thank god! 

Airbox Cover: For 2020 KTM gives the consumer an extra left side cover (upon purchase of vehicle) with holes to help the 250 SX-F breathe better. We tested both covers (with holes and without) and while the cover with holes installed made the KTM pull better up on top end, the cover without holes gave the 250 SX-F better bottom to mid range rpm response. If you’re riding wet conditions, it’s nice to know that you have a cover that will not allow water inside your airbox. 

Dunlop MX3S Tires: Thank you KTM for not falling for the Dunlop MX33 front tire trap just yet. The MX3S tires come standard for 2020 again on the KTM and we hope Dunlop allows manufacturers to run the 3S tires for 2021. Orrrrr. Design another soft to intermediate tire that is as good on lean angle as the 3S is. 

Husqvarna Or KTM?: I get this question a lot! If it was me I would prefer the KTM 250 SX-F because of the free feeling engine and the stiffer suspension spec. I do like Husqvarna’s rear end compliancy and handlebars more, but the engine rules the roost in the 250F class and to me the KTM engine is a little better. Yes, I am splitting hairs, but I try not to waffle on your questions! 

If you have any questions about this test or any others, you already know that we are here for you. We try to make your purchase the correct purchase. Email Kris@keeferinctesting.com for any burning q’s.