NGK LMAR8D-J Laser Platinum Spark Plug – 93444

The NGK Laser Platinum Spark Plug - LMAR8D-J (Part #93444) is an original-equipment-specification multi-ground spark plug engineered for high-compression, liquid-cooled and air/oil-cooled twin-cylinder adventure and roadster engines. Modern dual-overhead-cam (DOHC) cylinder heads feature compact combustion chambers with tight valve clearances, requiring a narrow 10mm thread diameter and a long 26.5mm thread reach to position the firing tip accurately within the combustion chamber while clearing water jackets.

Constructed with laser-welded platinum alloy firing surfaces on both the fine-wire center electrode and the dual ground electrodes, the LMAR8D-J maintains a consistent spark gap over extended service intervals. The dual ground electrode ("-J") configuration provides two distinct spark paths, reducing spark voltage demand, promoting complete flame kernel propagation across lean-burn fuel mixtures, and preventing fouling during low-RPM technical riding or high-altitude operation. Trivalent metal plating on the shell provides corrosion and anti-seize protection inside aluminum cylinder heads, while corrugated alumina silicate ceramic ribs prevent flashover under high ignition coil loads.

Features:

• Laser-Welded Platinum Center Electrode: Ultra-fine platinum alloy tip lowers required ignition voltage and resists spark erosion for long service life.

• Dual Ground Electrode (-J) Design: Twin ground straps optimize flame kernel growth, improve ignitability in lean fuel mixtures, and distribute wear across two firing surfaces.

• Compact 10mm Long-Reach Architecture: M10 x 1.0 thread pitch with a 26.5mm reach fits modern, narrow-angle 4-valve DOHC cylinder heads.

• Pure Alumina Silicate Ceramic Insulator: High-density ceramic core with corrugated ribs provides superior dielectric strength and rapid thermal transfer away from the firing tip.

• Solid Copper Core: Internal copper center conductor dissipates combustion heat efficiently to prevent pre-ignition under sustained high-load touring.

• Trivalent Metal Shell Plating: Anti-corrosion coating eliminates thread galling and seizing in cast aluminum cylinder heads without requiring external anti-seize compounds.

• 5k Ohm Ceramic Resistor: Suppresses electromagnetic interference (EMI) and radio frequency interference (RFI) to protect sensitive EFI sensors, ride-by-wire systems, and navigation electronics.

What's in the Box:

• 1x NGK Laser Platinum Spark Plug - LMAR8D-J (Stock #93444) with Protective Cardboard Thread Sleeve

• (Note: Sold individually. Twin-cylinder engines require 2 plugs per service; verify quantity required for your specific engine before checkout).

Fitment:

• 2013–2018 – BMW R 1200 GS & R 1200 GS Adventure
  

• 2014–2018 – BMW R 1200 RT

• 2015–2018 – BMW R 1200 RT

• 2015–2018 – BMW R 1200 R

• 2015–2018 – BMW R 1200 RS

• 2014–2023 – BMW R nineT

• 2017–2023 – BMW Urban G/S

Fitment Notes:

• Generation Distinction Warning: Fits 2013–2018 liquid-cooled 1170cc BMW Boxers and 2014–2023 R nineT models. DoesNOT fit 2019+ BMW R1250GS / R1250GSA ShiftCam engines (which require NGK LMAR8AI-10) or pre-2013 air/oil-cooled R1200GS Camhead/Hexhead engines (which require NGK MAR8B-JDS).

• Do Not Attempt to Adjust Spark Gap: The NGK LMAR8D-J comes pre-gapped from the factory to0.031" (0.8 mm) and features a fine-wire laser-welded platinum center tip flanked by two curved ground electrodes. Never insert a coin-style gap ramp or pry against the center electrode; prying against the brittle platinum tip will fracture the weld or chip the ceramic nose. If verifying gap with a wire feeler gauge, slide the wire gently between the center tip and each ground strap without applying leverage.

   

• Do Not Apply Anti-Seize to Threads: NGK spark plugs feature a shiny trivalent chromate plating engineered specifically to prevent thread seizing and galling in aluminum cylinder heads. Applying copper, nickel, or aluminum anti-seize compounds to trivalent-plated threads lubricates the threads excessively, increasing clamping force by up to 20% at the same wrench torque. Over-torquing a 10mm long-reach plug stretches the steel shell and can strip or crack the aluminum spark plug boss in the cylinder head. Always install the threads clean and dry.

   

• Strict M10 Torque & Crush Washer Seating: Narrow 10mm spark plugs have significantly lower structural shear limits than standard 14mm plugs.

  1. Blow out the deep spark plug well with compressed air before removing the old plug so trail sand does not fall into the cylinder.

  2. Thread the new LMAR8D-J into the cylinder head by hand using a rubber hose or thin-wall magnetic 14mm socket until the metal gasket washer contacts the head seat.

  3. For a new plug with an uncompressed crush washer, tighten1/2 to 2/3 of a turn past finger-tight, or torque strictly to7.2 – 8.7 lb-ft (10 – 12 Nm).

   

• Coil-On-Plug (COP) Boot Prep: On BMW R1200 liquid-cooled and R nineT boxers, the stick coils sit in exposed cylinder head wells subjected to wheel spray, water crossings, and high exhaust header heat. Apply a thin film of dielectric silicone grease to the inside lip of the rubber coil boot—never on the metal terminal tip—before snapping the coil onto the solid terminal nut. This seals out moisture and prevents the rubber boot from vulcanizing to the ceramic insulator over high mileage.

Cross-Reference:

• BMW: 12 12 8 532 942(12128532942)
• BMW: 12 12 7 726 112 (12127726112)

Part Number: 93444