2019 KTM 350 XC-F Project Bike Riding Impression

Enhancing the performance of a KTM 350 four-stroke off-road motorcycle.

Project bike builder Jay Clark believes the KTM 350 SX-F motocross bike is one of the best all-around dirt bikes you can buy. He feels a 350 is the optimal size for most riders, and that if you can only have one bike to ride at the motocross track and on the trails, the XC-F off-road model is just that bike. Clark put the 350 XC-F through its paces in stock trim and added a few aftermarket parts before doing a more extensive build. We rode the bike in stock trim before any modifications were done to it and we were impressed with the overall package, so when Clark notified us that the completed project bike was ready for us to test, we headed to Cahuilla Creek MX in Anza, California to see how it performed.

2019 KTM 350 XC-F ridden in desert.
Project bike builder Jay Clark’s latest creation for us to test was a 2019 KTM 350 XC-F.Spencer Owens

Since Clark works for Vertex Pistons, he put a high-compression piston in the engine. At only 40 hours, the KTM’s stock piston didn’t need to be replaced, but he wanted to add some extra power and make sure it was fresh. He also installed an FMF Factory 4.1 RCT full exhaust system and a KTM two-stroke air filter cage to get rid of the backfire screen.

2019 KTM 350 XC-F right profile in the desert.
A Vertex high-compression piston kit, FMF Factory 4.1 RCT full exhaust system, and Vortex X-10 ECU with custom mapping by Twisted Development were the main modifications done to the engine.Spencer Owens

Twisted Development mapped a stock ECU and a Vortex ECU for the bike. After testing both ECUs mapped by Jamie Ellis, Clark felt the stock ECU was very good and an excellent option for those on a budget. With the Vortex unit installed, he noticed the bike ran even better and had less of a tendency to flame out, so he left the Vortex installed for our test. A Blais Racing clutch weight was also used to give the KTM more of a torque feel down low.

2019 KTM 350 XC-F left profile in the desert.
Factory Connection massaged the WP suspension components, and Clark used a plethora of aftermarket parts to make it more trail-worthy.Spencer Owens

In stock trim, the 350 XC-F has a powerband that is similar to the 250 XC-F—a fair amount of bottom-end, decent midrange, and excellent top-end and over-rev. The modifications done to the engine enhanced the bottom-end hit, making it easier to ride. The KTM’s high-rpm power was not sacrificed either. Clark also had us try it with the optional spark arrestor screen insert in the muffler, which is included with the Factory 4.1 RCT aluminum unit. The spark arrestor added even more bottom-end and made the bike noticeably quieter.

2019 KTM 350 XC-F kicking up sand in the desert.
The modified 350 XC-F engine had more low-end power than stock.Spencer Owens

The WP AER 48 fork and WP shock on the XC-F models are fairly good, but are set up more for lower-speed, tighter trails. With that, they can be a bit too soft for higher-speed off-road riding and the motocross track. Being that Clark was setting the bike up to be more suited to off-road, but still wanting better performance from it on the motocross track, he had Factory Connection set the suspension up accordingly. The 350 XC-F had a firmer feel on small impacts like braking bumps on the motocross track and rocky parts of the trail, but not to the point to where it was uncomfortable. On faster sections, the WP units had much better hold up and less of a tendency to travel too quickly through the stroke, both of which enhanced predictability, making it easier to feel confident when riding aggressively. Riding the KTM on Cahuilla Creek MX’s trails and vet motocross track made it apparent that Clark achieved his goal of having a suspension package that could cross over between the trail and track.

2019 KTM 350 XC-F jumping in the desert.
With the included spark arrestor screen insert in the FMF muffler, the KTM’s bottom-end was further improved and also quieter.Spencer Owens

The 350 XC-F featured several more modifications, but some were done specifically to help with trail riding and the abuse it can do the bike and engine. A Trail Tech fan was used to reduce the chances of the engine heating up in tight sections, and an IMS coolant catch can was installed to help prevent coolant from escaping if the engine got too hot. IMS also provided a larger-sized fuel tank, alleviating the need to carry gas on longer trail rides. Enduro Engineering wraparound hand guards were installed to protect the rider's hands and to prevent the chances of catching a lever on bush-filled trails.

2019 KTM 350 XC-F turning in the sand.
The Factory Connection-modified suspension made the 350 XC-F better on higher-speed off-road sections and the motocross track than it was in stock trim.Spencer Owens

There were some more protection-type components used, and Clark admits the rest of the modifications were not as critical to the KTM’s performance. However, they transformed the 350 XC-F into a true show machine, making it hard for him to want to get it dirty. The custom DeCal Works matte finish graphics and MotoSeat cover were a couple of standout items. Clark even located orange pieces for the frame guards and airbox to make it a truly all-orange machine. Additional items used were Supersprox chain and sprockets, and Tusk wheels. Being that Clark is well-known as “the Dunlop guy,” he of course mounted Dunlop AT81 off-road tires on the aftermarket wheels.

2019 KTM 350 XC-F weaving between boulders and trees.
A Trail Tech fan was used to help keep the bike cool in tight sections of the trail.Spencer Owens

The 2019 KTM 350 XC-F is a great motorcycle in stock trim and Clark's modifications made it that much better of a bike that can be ridden off-road and at the motocross track nearly equally well—a true testament to what a cross-country dirt bike should be. We had a great time riding it and would like to thank Clark for building it for us and Cahuilla Creek MX for allowing us to test the bike on a private ride day at its Anza, California, facility.

2019 KTM 350 XC-F jumping in the desert.
The Factory Connection suspension made the 350 XC-F much more predictable and enjoyable to ride on the motocross track with additional control in the middle of the stroke.Spencer Owens
2019 KTM 350 XC-F project bike riding up mountain through rocks.
After a full day of riding Clark’s 2019 KTM 350 XC-F project bike, we can confidently say he improved it for both trail riding and motocross track use.Spencer Owens

Parts List

Vertex Pistons vertexpistons.com
High-compression piston kit (ring, pin, and clips)
FMF Racing fmfracing.com
MegaBomb stainless steel header pipe Factory 4.1 RCT aluminum muffler
Twisted Development td-racing.com
Vortex X-10 ECU Custom ECU mapping
Cometic Gasket cometic.com
Top-end gaskets
Supersprox supersproxusa.com
Front sprocket (14-tooth) Stealth rear sprocket (50-tooth)
Gold Enduro Race chain (G520-EXT-120)
Factory Connection factoryconnection.com
Suspension rebuild, service, and setup (springs and valving)
Polisport polisport.com
All-orange plastic Orange mud flap
IMS Products imsproducts.com
Coolant recovery tank 2.6-gallon fuel tank
DeCal Works decalmx.com
Semi-custom graphics kit Preprinted number plate backgrounds
Works Connection worksconnection.com
Factory II stand Front and rear brake caps
Rotating bar clamp
Steering stem nut Rear chain adjuster blocks
Front axle nut Engine plugs
Dunlop Tires dunlopmotorcycletires.com
AT81 front, 90/90-21 AT81 rear, 110/100-18
Uni Filter unifilter.com
Air filter
Scar Racing scar-racing.com
Titanium footpegs
TM Designworks tmdesignworks.com
Rear chain guide
Hinson Clutch Components hinsonracing.com
Fiber plate kit Clutch spring kit
Billetproof clutch cover
MotoSeat motoseat.com
Seat cover
Trail Tech trailtech.net
Radiator fan
Motion Pro motionpro.com
Titan throttle tube Grip glue
Renthal renthal.com
603 Fatbar
Bullet Proof Designs bulletproofdesigns.com
Rear swingarm guard Shock knuckle guard
Fasst Co. fasstco.com
Rear brake return spring Rear brake clevis
Enduro Engineering enduroeng.com
Clutch cylinder guard Full-coverage hand guards
Tusk tuskoffroad.com
Full wheel set Oversize rotor and adaptor bracket
Rear rotor Rotor and sprocket bolts
Blais Racing Services blaisracingservices.com
7-ounce clutch weight
KTM ktm.com
Orange airbox pieces Orange frame guards (off of a 2019 450 SX-F Factory Edition)
PowerParts skid plate Two-stroke air filter cage