KTM Performance guide
KTM 350/500
Performance Guide
2017+ · Intake, Exhaust & ECU · Real Dyno Numbers, Not Forum Numbers
What uncorking actually does — real Dynojet 168 numbers, at the wheel
2025 KTM 350 EXC-F
+11.2 hp · +31%
2025 KTM 500 EXC-F
+21.5 hp · +56%
Tested on our Dynojet 168 at 2,300 ft. Intake opened, exhaust opened, fuel corrected — the full ladder, not any single mod.
Why these bikes feel down on power
Here's the thing nobody at the dealer tells you: your bike isn't underpowered. It's restrained. KTM builds a genuinely strong engine, then straps it down with the equipment it takes to pass noise and emissions testing in every market it sells in. That's the price of a green sticker and a plate.
Every one of those restraints is a knob turned the wrong way for power. Pull them off in the right order and you're not adding anything exotic. You're just giving the motor back the air, fuel, and breathing room the engineers designed in and the regulators made them hide.
Read this before you buy or cut anything
This is a race build. That's not a warning, it's the whole mechanism.
Every mod on this page works by removing the exact equipment that keeps your bike street legal: the sound restriction in the exhaust and the emissions gear on the engine. That's not a side effect. It's why the power comes back. Which means everything here is sold and described for closed-course competition use only.
We'll be straight with you the way we'd want it. Once that equipment comes off, the bike is no longer legal on public roads, it will not pass an emissions or smog inspection, and it is not CARB or EPA compliant. What you do with your own bike is your call and your responsibility, not ours.
The uncork ladder
Where your money and effort go furthest, top to bottom. The tune matters most and has to match whatever hardware you run. The exhaust is the biggest airflow gain. The reeds are free extra power. You don't have to do all of them. Smog delete is optional and makes no power at all.
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01
Correct the fuel
The one that actually makes power. Once you open the bike up, a stock ECU can't add the fuel that extra air needs, so a reflash or race ECU is what turns airflow into real, safe horsepower. Whatever exhaust and intake you end up running, the map has to be built to match it.
Why it's not optional: the stock O2 sensor can only trim fuel in the cruise zone, roughly 14.5 to 16.5 AFR. It can't reach the 13 to 14 range where the engine makes safe best power. Open the airflow without a tune and we've watched a stock ECU log AFR in the upper 17s on our dyno. That's lean enough to cook a piston. -
02
Open up the exhaust
The stock system is strangled on purpose, and this is where the biggest airflow gain on the bike lives. Three ways up, each one buying a little more than the last:
Billet end cap Pro Moto Billet cap on the stock can. Full-band airflow, cooler running, stock look, and the friendliest price. The value play.Slip-on A proper muffler. Adds real weight savings and sound character on top of the airflow. Pick by riding style, table below.Full system Header and muffler together. The last of the airflow and the loudest of the bunch. Nobody needs it, plenty want it, and that's fine. -
03
Pull the intake reeds
Free power, and you delete a real failure point while you're at it. Those carbon petals are documented to snap off and go looking for your valves, and they can pop backwards and choke the airflow instead of helping it. You give up a little low-end smoothness and gain a little intake growl. Worth it.
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Optional: complete smog delete
Not part of the power path, so it sits off the numbered ladder. Charcoal canister, vapor lines, the whole emissions rat's nest. It makes no power and we won't pretend otherwise. What it does is delete a pile of maintenance points, failure points, and weight, and make everything else on the bike easier to reach. Do it whenever you feel like it, or never. Trade-off: more fuel smell in an enclosed trailer or van.
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✕
The velocity stack: don't
The internet insists the air boot collapses without reeds. It does not. We put one on the dyno and watched it hand back 2 to 8 hp across the powerband. You'd be spending money to go slower, which is a hell of a way to spend money.
Pick your pipe
They all need a matching tune, so ignore that. What actually separates them is how loud, how it hits, and whether it survives a day of tight trail. Swipe sideways on your phone.
| Option | Cost | What you get | Noise | Best for | The catch |
|---|---|---|---|---|---|
|
Best value Pro Moto Billet end cap |
$ | 42 mm outlet, full power potential unlocked, engine runs cooler, stock can and stock look | Louder. Ultra-silent insert available. | Anyone who wants the whole airflow gain without buying a muffler. | Honestly, nothing. This is the pick if you're not going to spend pipe money. |
|
Best all-around Graves muffler |
$$$ | Strong, smooth power through the whole rev range. Up to 1.3 lb saved. | Louder. Removable DB killer / spark arrestor included. | Every riding style, top to bottom. If you're buying exactly one pipe, buy this. | Cost. And the carbon end cap does not enjoy being crashed on. |
| Yoshimura muffler / full system | $$$ | Strong, smooth power through the whole rev range. | Quite loud. Removable DB killer / spark arrestor. | All riding levels. | Nearly stock weight, so you're not buying grams. May melt your turn signal. Fragile carbon cap. |
| FMF 4.1 slip-on | $$ | Full-band airflow, hard punchy hit, up to 1.1 lb saved. | Very loud. Your riding buddies will have opinions. | Supermoto, snow bike, wide-open desert. | Snappy, harsh down low. Not what you want in tight trail. May melt your turn signal. Fragile carbon cap. |
|
It's an option Stock end cap mod |
Free | Some airflow. Cooler running. Stock look. Better than nothing. | Louder. | Riders on a strict zero-dollar budget. | Still very restrictive at a 26 mm outlet, so you're leaving real power on the table. Get it wrong and you've voided spark arrestor compliance. We'd rather sell you the billet cap. |
| Stock cone resonator removal | Free | Mid and top-end gain. | Drone. Genuinely annoying drone. | Fast open-terrain riders only. | Kills bottom-end torque and it's a miserable job. Don't do this to a trail bike. |
|
Nope Intake velocity stack |
$ | Nothing. Measurably nothing. | — | Nobody. | Cost 2 to 8 hp on our dyno. Save your money and buy fuel. |
"Do I need a new map?"
A tune is built for specific hardware. Change enough of it and your map is describing a bike you don't own anymore. Here's exactly when that matters, and when you can relax.
| What changed | New map? | Why |
|---|---|---|
| Stock exhaust → slip-on or full system | Yes | The big one. Your map was fueling for a strangled pipe. The new one flows way more air, so the same fuel over more air means it runs lean. Call us. |
| Stock exhaust → opened end cap | Yes | Same reason, smaller number. Airflow changed, so fueling has to change. |
| One brand of slip-on → another | Usually no | You're already in the open-exhaust world and the map is already built for it. Different cans flow close enough that you'll be fine. If something feels off after the swap, tell us what you've got and we'll sort it. |
| Pulled the reeds after you were already tuned | No | Our maps already account for it. Pull them and ride. |
| Complete smog delete | No | No airflow change, no power change, nothing for the map to do. |
| Sprockets, tires, bars, suspension | No | The engine has no idea you did any of that. |
| Moved somewhere much higher or lower | No | The baro sensor is on it. There's a whole sheet on this, linked at the bottom. |
"My exhaust isn't in the dropdown"
Order it anyway and tell us exactly what you're running. Don't guess at the closest option and hope. Drop it in the order notes or email us, and we'll build the map around the hardware you actually have.
Buying the pipe later? Say so when you order. We'd much rather load the right map today than reflash it for you in three weeks.
What lean actually feels like
Surging or hunting at steady throttle. Popping hard on decel. Hanging idle that won't come down. Running hotter than it used to, headers glowing, plastics getting toasty. More stalling in the tight stuff, not less. If you opened up the airflow and skipped the tune, you're not imagining a single bit of it.
Pick your ECU or tuner
Seven ways to correct the fuel, and they're nowhere near equal. It's the priciest call on the page, so it gets its own sheets instead of a cramped footnote here.
The tuning comparison chart
All seven, side by side. TacoFlash, ERM, JD, Power Commander 6, Vortex, AIM, GET. Price, traction control, maps, diagnostics, no marketing.
Start here →Stock reflash vs GET SX1
For most people it comes down to these two. Best bang for the dollar against the best platform in dirt biking. Here's how to actually choose.
The real decision →What makes the TacoGET so good
Ten-mode traction control, launch control, WiFi app tuning, built-in baro sensor, and a lifetime map and hardware warranty when you buy it from us.
The deep dive →The 30-second version
Best bang for the dollar — TacoFlash ship-in reflash. Send us your stock ECU. Fuel and ignition both, no extra hardware bolted on, lifetime map support. Add the map switch for dual maps, traction control, and quick shift.
Want to flash it in your own garage — TacoFlash on Power Vision 3. Same tune, no shipping, and the device doubles as an OBD2 scan tool for your other bikes.
Best there is — the GET SX1. Everything above, plus 10-mode traction control, launch control, and tuning from your phone in the parking lot.
Zero dollars. Twenty minutes.
Try these before you buy anything
Half the stall complaints we hear vanish with these four, and not one of them costs a cent.