MXA MOTOCROSS RACE TEST: 2018 KTM 85SX
Q: FIRST AND FOREMOST, IS THE 2018 KTM 85SX BETTER THAN THE 2017 MODEL?
A: Yes. KTM started with a clean slate for the 2018 KTM 85SX. It was a bike that was built from the ground up.
Q: WHAT ARE THE CHANGES TO THE KTM 85SX FROM 2017 TO 2018?
A: KTM improved the overall powerband and gave the bike a more efficient chassis. Here are the mods that KTM made to the 2018 85SX.
(1) Cylinder. The new cylinder was designed around an all-new power-valve system. This system is adjustable with the turn of a dial—just like the KTM 125SX and 250SX two-stroke power valves. The adjuster can change the power delivery by controlling when and how quickly the valves open and close.
(2) Crankshaft. The crankshaft is lighter while having more inertia. The optimized balance reduces vibrations.
(3) Clutch. Its diaphragm spring clutch is smaller, stronger and more compact.
(4) Crankcases. The crankcases are designed with the internal shafts arranged as close as possible to the center of gravity.
(5) Transmission. Weight was shaved from the gears, shafts and forks.
(6) Frame. The chromoly steel frame is almost 1 pound lighter. This is on top of a 7-percent increase in torsional rigidity and a 25-percent decrease in longitudinal stiffness.
(7) Forks. WP’s well-received AER 43mm air forks are standard equipment.
(8) Subframe. The subframe is lighter and more compact.
(9) Cooling system. The 85SX now has integrated crankcase cooling with twin radiators. Redesigned and reinforced radiator shrouds and a grill that guards the radiators in a crash.
(10) Bodywork. The bodywork is based on the full-sized KTM SX models.
(11) Airbox. The airbox features a no-tools approach like its big brothers.
At first glance the 2018 KTM 85SX looks like a KTM 125SX—until you notice that the bike and the stand are out of proportion. As minicycles go, this is a very modern-looking 85.
Q: WHAT DOES THE 2018 KTM 85SX COST?
A: At $5799, the 2018 KTM 85SX is over $1000 more than all its Japanese competitors; however, it is less expensive than the Italian-made, Loretta Lynn-winning TM MX85, which runs for $8199.
Q: DID KTM CHANGE THE GEOMETRY OF THE 85SX?
A: No. The dimensions of the 2017 KTM 85SX were spot-on, and KTM’s engineers didn’t want to fix something that wasn’t broken. The steering head angle remains at 24 degrees, the wheelbase at 50.8 inches, ground clearance at 13.9 inches and the seat height at 33.7 inches.
Q: WHY DOES KTM CONTINUE TO UPDATE ITS MINI 85SX WHEN THE “BIG FOUR” JAPANESE COMPETITORS RARELY MAKE ANY UPDATES?
A: KTM believes that money spent R&Ding the KTM 50SX, 65SX and 85SX is money well spent, because it gets kids as young as 6 years old hooked on orange. If a kid races a KTM 65SX, he will most likely buy a KTM 85SX when he grows taller. If he races a KTM 85SX, he will most likely buy a KTM 125SX, 250SXF and eventually a 450SXF. KTM’s marketing plan is to get them while they are young and hopefully turn them into lifelong customers. Although Kawasaki and Yamaha have 65cc motocross bikes in their 2018 lineups, they lack the full range of models that KTM offers—not just in motocross, but in offroad, enduro and dual-sport as well. No manufacturer has spent as much money and energy developing its mini portfolio as KTM—and a walk through the pits at any Amateur National will confirm that it’s working.
Q: DO THE WP AER FORKS WORK AS WELL ON THE 85SX AS ON THE BIG KATOOMS?
A: Yes. KTM has the 43mm WP AER air forks dialed in for a wide range of riders. We had big and small test riders on the 85SX, and the flexibility of the setup option was amazing. The big riders never complained about bottoming, while the small riders never complained about harshness. We applaud WP for becoming a solid player in the suspension world. It was a long, hard road, mostly for the racers who had to live through the 4CS period, but WP has found the secret sauce. To find your perfect air pressure, put a zip-tie on one fork leg and go ride. If the zip-tie is 2-1/2 inches short of bottoming, lower the air pressure. Keep lowering it until you are 1 inch from bottoming. That is your air pressure.
Q: DID KTM MAKE THE SWITCH FROM KEIHIN TO MIKUNI LIKE THEY DID ON THE 125SX AND 250SX?
A: No, thank goodness. The first year of the Mikuni carburetors with the KTM 125SX and KTM 250SX were fraught with peril. Thankfully, jetting the 28mm Keihin PWK carburetor on the 2018 KTM 85SX was a no-brainer. We fiddled with the air screw for climate changes but didn’t change anything else.
Q: JUST HOW POWERFUL IS THE 85SX?
A: Powerful enough to make our Pro test riders loop out. Every rider underestimated the power of the small but mighty engine. This is a racer’s bike. It doesn’t have much bottom end, but once it hits the midrange, it explodes with power. It isn’t all that more powerful at peak than the 2017. Both are in the 21.5-horsepower range, but it has seen a healthy increase in midrange torque. If you want to tame the power or move it, you can turn the power-valve adjuster. It is easy to do. Go ride the 85SX and then stop and turn the power-valve adjuster on the right side of the engine 1/8th of a turn clockwise. Ride the bike again, come back to the pits and turn it 1/8th of a turn counterclockwise (from stock). Once you find the direction of rotation that you like best, continue to make small adjustments to dial it in. It makes a big difference in the power delivery, so it is worth the time and effort to test several settings.
Q: WHAT DID WE HATE?
A: The hate list:
(1) Preload ring. The plastic preload ring needs to be beefed up. We never hit it with a punch, because it will deform; instead, we use a long, flat-bladed screwdriver to pry against the frame.
(2) Power-valve adjuster. KTM’s power valve is adjusted with a Robertson wrench. Yeah, we don’t own one of those, either. We wedge a flat-bladed screwdriver in the slot to make spring preload adjustments. KTM Power Parts and Nihilo Concepts both offer aftermarket Robertson wrenches that fit the KTM power valve’s square fixture.
(3) Bleed screw. The air-fork bleed screw is a #15 Torx. We used an 8mm hex-head T-handle instead. A Phillips screw would work better, if anyone at the factory is listening.
(4) Bar pad. We don’t care for the small, hard bar pad, as it doesn’t offer much protection. What is wrong with the bar pads that come on the KTM big bikes?
(5) ODI grips. We like the ODI lock-on grips, but the clutch side is locked on with a #15 Torx. If you want to change the grips, you have to have a #15 Torx.
(6) Airbox. Although this airbox is similar to its bigger brothers, the side cover is very hard to get off. We use a flat-bladed screwdriver to pry the cover off to get to the air filter, thus we can’t call it a no-tools airbox.
Q: WHAT DID WE LIKE?
A: The like list:
(1) Powerplant. This bike is fast, really fast.
(2) Brakes. They are still the best in their class by a landslide.
(3) Hydraulic clutch. Self-adjusting hydraulic clutches don’t come on any Japanese motocross bikes, regardless of their engine size, but the KTM 85SX has one.
(4) Forks. We love the WP AER forks. They are simple, light, understandable, easy to use and very good.
(5) Power-valve adjuster. We like being able to adjust the power spread for different riders and terrains.
Q: WHAT DO WE REALLY THINK?
A: We think KTM loves to win. That is why they spend incredible amounts of money on R&D every year. In the 85cc class, the Japanese brands don’t even put up a fight. Some Japanese 85s are over a decade old, with little more than cosmetic updates. The KTM 85SX is a turnkey factory bike for the junior set. Bottom line? This bike offers a great engine, suspension and chassis right off the showroom floor.
MXA’S 2018 KTM 85SX SETUP SPECS
This is how we set up our 2018 KTM 85SX for racing. We offer it as a guide to help you find your own sweet spot.
WP AER 43MM FORK SETTINGS
First, focus on balancing out the bike for your weight by adjusting the air pressure in the forks. If the forks are diving into the corners, go up a few psi. If they are rigid, lower the psi. These forks offer great bottoming resistance, so going softer for a plusher ride is not an issue. For hardcore racing, we recommend this fork setup for the 2018 KTM 85SX (stock settings in parentheses):
Air pressure: 73 psi
Compression: 12 clicks out
Rebound: 12 clicks out
Fork-leg height: Stock
Notes: Don’t worry about checking the WP AER fork’s air pressure each and every time you hit the track. Do, however, bleed both of the air screws on top of the forks.
WP SHOCK SETTINGS
KTM has stuck to the PDS no-linkage stock system with the 85SX. Now that MXA test riders have some distance from the PDS days, and KTM has had more time to refine the spring rates, PDS doesn’t seem to hinder the performance of the KTM 85SX. Our test riders did not change much on the stocker, as they started with the stock numbers and stayed very close to that baseline. For hardcore racing, we recommend this fork setup for the 2018 KTM 85SX (stock specs are in parentheses):
Spring rate: 40N/m
Race sag: 120mm
Hi-compression: 2 turns out
Lo-compression: 15 turns out
Rebound: 15 turns out
Notes: The stock shock settings are in the ballpark.
KEIHIN PWK 28MM JETTING SPEC
Here’s what we ran in our 28mm PWK carb.
Main jet: 142
Pilot: 48
Needle: NRKC
Clip: 3rd position
Air screw: 2 turns out
THE GEAR: Jersey: Thor Fuse High Tide, Pants: Thor Fuse High Tide, Helmet: Thor Verge, Goggles: Thor Sniper Chase, Boots: Sidi Crossfire 2
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