Dedicated Subsystem WorkbenchPlatform Gen: 2016–2024

2021 Triumph Bonneville T120 Charging System, Stator AC Output & Battery Health

Stator 3-phase AC voltage at 5,000 RPM, coil resistance, regulated DC voltage, battery code YTX12-BS, CCA rating, and multimeter charging diagnostic steps for 2021 Triumph Bonneville T120.

Gen 2016–2024

Factory Platform Compatibility: All workshop fluid capacities, maintenance milestones, torque specifications, and consumables on this specification sheet are factory-identical across model years 2016 through 2024.

Select Model Year:(Active: 2021)

2016 2017 2018 2019 2020 2021 2022 2023 2024

Engine

1200cc

Drive

525

Cooling

Liquid-Cooled

3-Phase Charging System & Battery Diagnostic Flowchart

Yuasa & OEM Standards

Multimeter troubleshooting protocols, cold cranking amps (CCA) ratings, 3-phase stator AC outputs, and regulator-rectifier health verification.

Shop YTX12-BS Batteries

OEM Battery Code

YTX12-BS (VRLA / AGM Maintenance-Free)

Cold Cranking Rating

180 CCA

Capacity (10HR Rate)

10 Ah (12V)

Regulated Output Spec

14.2 - 14.8 V DC (at 5,000 RPM with High Beam)

Key-OFF Parasitic Limit

< 1.2 mA (Key OFF ignition latch)

Enter Multimeter DC Voltage Reading

V DC

Multimeter Test Diagnosis

Enter your multimeter terminal reading on the left to view instant diagnostic interpretations and recommended workshop actions.

OEM Factory AGM BatteryExact OEM Fit

Yuasa YTX12-BS High Performance AGM Battery

Dimensions: 150 L × 87 W × 130 H mm • Weight: 9.2 lbs (4.2 kg). Pre-filled absorbed glass mat technology engineered for heavy vibration resistance.

Lithium LiFePO4 UpgradeUp to 70% Lighter

Antigravity ATX-12 Re-Start (360 CCA / 2.0 lbs)

Features built-in RE-START jump starting reserve. Never stranded by dead lights: press the restart button on the top terminal to crank the motorcycle without jumper cables.

Smart Maintainer SpecBattery Life Extension

12V AGM / Float 1.0A

Standard Charge Rate: 1.0A (Max 2.0A). Automated desulfation & float maintenance ensures full capacity retention during off-season winter storage.

Recommended Parts: Yuasa YTX12-BS High Performance AGM Battery • OptiMate 4 Quad Program 1.0A Smart Battery Tender / Charger

Shop Smart Battery Chargers Find Direct-Fit Batteries

IGNITION ENGINEERING, HEAT-RANGES & COMBUSTION DIAGNOSTICS

OEM Spark Plugs • Heat-Range Dissipation • Coil Resistance • Visual Combustion Reading Matrix

FACTORY CERTIFIED SPECIFICATIONS

Factory Standard Plug

NGK LMAR8A-9

2 Plugs (1200cc 270° Parallel Twin)

Electrode Spark Gap

0.8 - 0.9 mm (0.031 - 0.035 in)

M10 x 1.0 • 26.5 mm Reach

Hex Drive & Socket Spec

14 mm Bi-Hex (Thin-Wall)

Use magnetic rubber-insert thin socket

Tightening Torque (NM)

12 N·m

1/2 turn after finger seat (crush washer)

Stick Coil Resistances

Pri: 0.80 - 1.10 Ω at 20°C

Sec: 9.5 - 12.5 kΩ at 20°C

Service & Replacement

Inspect: 10,000 miles (16,000 km)

Replace: 20,000 miles (32,000 km)

SPARK PLUG HEAT-RANGE & METALLURGY SELECTOR

Compare OEM standard, fine-wire precious metals, and ambient/duty cycle thermal dissipation paths

Verified Part Specification

NGK LMAR8A-9

FACTORY SPECIFICATION

Metallurgy & Center Tip Architecture

Copper Core / Solid Nickel Alloy Ground Electrode

Thermal Dissipation Path & Physics

Standard OEM factory thermal dissipation rate. Calibrated to stabilize ceramic nose temperature between 500°C–800°C across mixed street, highway, and mountain riding.

Operating Application Envelope

Stock engines, factory ECU mapping, general commuting, and standard touring. Recommended for all baseline maintenance schedules.

Ignitability & Coil Voltage Demand

Standard spark kernel size. Standard secondary coil demand (~15–20 kV). Solid copper core ensures rapid heat conduction away from tip.

SPARK PLUG READING & COMBUSTION DIAGNOSTICS ANALYZER

Interactive visual diagnosis: Match your ceramic insulator tip and electrodes to detect AFR, timing, oil intrusion, and thermal overload

Normal Clean — Optimal Combustion Equilibrium

OPTIMAL COMBUSTION

Thermal Operating Range: 500°C – 800°C (932°F – 1,472°F) • Self-Cleaning Pyrolysis Window

Visual Insulator & Electrode Profile

Ceramic insulator nose is light grayish-tan, beige, or light brown. Firing tip and electrodes are dry with minimal combustion deposits. Ground electrode edges remain crisp without rounding or erosion.

Multimeter Electrical Resistance Test

Insulation Resistance > 10 MΩ (Infinite DC resistance between center terminal and steel shell). Dielectric barrier is pristine; zero spark leakage to cylinder head ground.

Probable Root Causes

Optimal air/fuel ratio across all throttle positions (stoichiometric 14.7:1 cruise, 12.8:1–13.2:1 power enrichment)
Correct spark plug heat range precisely matched to engine displacement and cooling efficiency
Ignition timing and coil dwell saturation within factory parameters
Healthy piston rings and valve guide seals with minimal oil blow-by

Prescribed Workshop Remediation Action

No mechanical intervention required. Inspect gap with wire-style feeler gauge and reinstall to factory torque specification.

Coil-on-Plug (COP) / Stick Coil Multimeter Bench Testing Protocol

Step 1 • Primary Circuit

Set DMM to lowest Ω range. Probe between Terminal 1 (+12V switched) and Terminal 2 (ECU trigger pin). Normal reading: 0.80 - 1.10 Ω at 20°C at 20°C.

Step 2 • Secondary Circuit

Set DMM to kΩ range. Probe between Terminal 1 and the high-voltage spark plug spring terminal inside the boot. Factory spec: 9.5 - 12.5 kΩ at 20°C at 20°C.

Step 3 • Dielectric Boot Inspection

Flex silicone boot under bright light. Check for pinholes, white powdery dielectric breakdown tracks, or hardened silicone causing high-voltage flashover to the cylinder head spark plug tube.

Direct-Fit Ignition Components & Workshop Sockets

Authentic laser iridium plugs, thin-wall magnetic sockets, and OEM replacement stick coils

Find Direct-Fit Spark Plugs Thin-Wall Magnetic Sockets

Triumph Diagnostic Fault Codes & Multimeter Bench Testing

FI & OBD2 Decoder

Authentic factory ECU fault codes, sensor resistance specifications, and harness pinout troubleshooting.

Launch Full Triumph DTC Engine→

Code P0105Manifold Absolute Pressure (MAP)

MAP sensor electrical circuit malfunction / range error.

Test: Verify 5.0V VRef and 2.5-3.0V signal key-on engine-off.

Code P0115Engine Coolant Temp (ECT)

ECT sensor circuit open, short, or out of plausible range.

Test: Measure NTC thermistor: ~2.5 kΩ at 20°C, 300 Ω at 80°C.

Code P0335Crankshaft Position Sensor (CKP)

CKP sensor electrical circuit or missing pulse teeth.

Test: Measure VR magnetic pickup coil resistance (typically 200-600 Ω).

Looking for other error codes, sensor pinouts, or OBD2/Euro 5 codes?

View All 68 Multi-Brand Diagnostic Trouble Codes →

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 #24V785000ELECTRICAL SYSTEM:WIRING:CONNECTORS/PLUGS/RECEPTACLES

Received: 21/10/2024▼

Defect Description

Triumph Motorcycles America, Ltd. (Triumph) is recalling certain 2022-2024 Bonneville T100, T120, T120 Black, 2022 Triumph Street Scrambler, Street Scrambler Sandstorm, Street Twin, Street Twin Goldline, 2023-2024 Scrambler 900, and Speed Twin 900 motorcycles. The wiring between the alternator and main harness connector may short circuit and overheat.

Safety Hazard / Consequence

Overheated wiring increases the risk of a fire or crash.

Factory Remedy & Repair Action

Dealers will install a new wire alignment clip, free of charge. Owner notification letters were mailed November 18, 2024. Owners may contact Triumph customer service at 1-678-854-2010. Triumph's number for this recall is SRAN 627.

Manufacturer Notes: Owners may also contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153) or go to nhtsa.gov.

NHTSA #26V078000ELECTRICAL SYSTEM:ALTERNATOR/GENERATOR/REGULATOR

Received: 11/02/2026▼