Dedicated Subsystem WorkbenchPlatform Gen: 2017–2024

2023 KTM 390 Duke Suspension Hydraulics, Fork Fluids & Sag Tuner

Front fork travel, rear shock travel, spring preload, damping click baselines, and dynamic rider sag calculator for 2023 KTM 390 Duke.

Technical PassportOEM VERIFIED

Engine

373cc

Cooling

Liquid-Cooled

Final Drive

520 Chain

Engine Oil

1.60 L (1.69 US qt)

Spark Plug

Bosch VR5NEU / NGK LKAR8A-9

Front Tire

110/70R17

Gen 2017–2024

Factory Platform Compatibility: All workshop fluid capacities, maintenance milestones, torque specifications, and consumables on this specification sheet are factory-identical across model years 2017 through 2024.

SPECS-TO-CART BUNDLESFactory Direct-Fit Maintenance Bundles Available

1-Click verified Motul engine oil service kits, race filters, spark plugs, and brake fluid pre-measured for this 2023 KTM 390 Duke.

Configure Service Bundles→

Select Model Year:(Active: 2023)
8 Production Years (2017–2024)

2017 2018 2019 2020 2021 2022 2023 2024

Suggested Items4 Verified Workshop Consumables Available for this Job

View Suggested Items ↓

Suspension Hydraulics, Fork Fluids & Interactive Sag Tuner

Showa • KYB • WP Standards

OEM hydraulic capacities, air-gap measurement standards, clicker baselines, and mathematical rider sag tuning.

Shop Fork Seals & Wipers

Fork Architecture

Inverted USD Open Cartridge (43mm WP APEX)

Oil Volume Per Leg

450 ml (15.2 US fl oz) per leg

OEM Fluid Specification

Motorex Racing Fork Oil 4W (SAE 4W)

Air-Gap Spec (Oil Level)

110 mm (4.33 in) compressed, spring removed

Fork Seal Dimensions

43 x 52.9 x 11.4 mm

Total Suspension Travel

Front: 142 mm • Rear: 150 mm

Target Rider Sag: 36 - 42 mm (25 - 30% of 142 mm travel)

Front Preload Baseline

Non-adjustable internal linear coil

Rebound Damping Baseline

Split-damping circuit (non-adjustable)

Compression Damping Baseline

Split-damping circuit (non-adjustable)

Target Free Sag (Unladen)

20 - 26 mm

Enter 3-Point Sag Measurements (mm)

L1: Extended

L2: Static Bike

L3: In Full Gear

Suspension Sag Diagnosis & Geometry Status

Enter your extended, static, and rider measurements on the left (or select a preset) to compute exact sag percentages and spring preload recommendations.

Factory Fluid StandardDirect Spec

Motul Factory Line Fork Oil 5W (1 Liter)

Formulated with anti-foam agents and shear-stable viscosity index improvers to prevent damping fade under aggressive riding heat.

Fork & Dust Seal KitExact Stanchion Fit

All Balls Racing 43mm Fork & Dust Seal Kit

Features directional triple-lip rubber seal profile and external garter springs engineered to withstand heavy stanchion flex without weeping.

Air-Gap Tuning PhysicsBottoming Control

110 mm (4.33 in) compressed, spring removed

Trapped air column acts as a progressive spring in final 30% of stroke. Adding +5mm oil increases bottoming resistance without stiffening small bump compliance.

Recommended Maintenance Parts: Motul Factory Line Fork Oil 5W (1 Liter) • All Balls Racing 43mm Fork & Dust Seal Kit

Shop Fork Fluids Find Direct-Fit Fork Seals

Official NHTSA Safety Recalls & Technical Bulletins

2 Active Campaigns

U.S. Department of Transportation compliance database (Title 49 U.S.C. Chapter 301).

Verify VIN on NHTSA.gov

The U.S. National Highway Traffic Safety Administration reports 2 safety recall campaigns associated with this platform. Independent repair shops and riders should confirm that authorized dealership warranty remedies have been applied.

NHTSA #25V740000FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY:FILLER PIPE AND CAP

Received: 30/10/2025▼

Defect Description

KTM North America, Inc. is recalling certain 2024 390 Duke, 250 Duke, 990 Duke, Husqvarna Vitpilen 401, and Husqvarna Svartpilen 401 motorcycles. The seal on the fuel filler cap may develop cracks and leak fuel.

Safety Hazard / Consequence

A fuel leak increases the risk of fire or injury.

Factory Remedy & Repair Action

Dealers will inspect and replace the fuel cap gasket, free of charge. Owner notification letters were mailed December 15, 2025. Owners may contact KTM customer service at 1-888-985-6090. Vehicle Identification Numbers (VINs) involved in this recall will become searchable on NHTSA.gov March 31, 2026.

NHTSA #25V825000ENGINE AND ENGINE COOLING:ENGINE:ENGINE CONTROL MODULE (ECU/ECM):SOFTWARE

Received: 01/12/2025▼

OEM Workshop Archives

Official Factory Service Bulletins & Field Updates

1 Documented Bulletin

Bulletin #KTM-25V598Safety Recall KTB2606 / HTB2603: Sealed E-Throttle Twist Grip Assembly & Adaptation Reset

Source: KTM_Recall25V598_RCRIT-25V598-9541.pdf

Mandated Torques:E-Throttle Housing Clamp Screws (2x M4): 3.5 N·m (31 in-lb)Handlebar End Weight Screw (M6): 20 N·m (15 lb-ft)Handlebar Switchgear Screws (M4): 2.0 N·m (18 in-lb)Front Brake Master Cylinder Clamp (M6): 5 N·m (44 in-lb)

Consumable Specs:N/A

Genuine Part Numbers:Exchange Throttle Cmpl. (390 Adv / Duke / 401) (95802010044)Exchange Switch Control RH (RC 390) (94811074000)EJOT PT Screw K40×12 (0081040121)Handlebar Grip Right (90102021000)

NHTSA Recall 25V-598 & 26V-196Bulletins KTB2606 & HTB2603