Twin Air 1.8 Bar Replacement Radiator Pressure Cap

The Twin Air 1.8 Bar High-Pressure Radiator Cap (177900) is a critical cooling system upgrade designed to prevent coolant loss and engine overheating in high-demand off-road conditions. Stock motorcycle radiator caps are typically rated at 1.1 bar (15.9 psi), which allows engine coolant to boil at approximately 252°F (122°C). In slow-speed technical single-track, deep sand, or heavy mud, engine temperatures quickly surpass this threshold, causing the factory cap to vent and boil off coolant.

By increasing internal cooling system pressure to 1.8 bar (26.1 psi), this high-pressure cap elevates the boiling point of water-based coolant to approximately 278°F (136°C). This higher threshold keeps the coolant in liquid form longer, ensuring continuous heat transfer away from the cylinder head and water jacket. Featuring an integrated temperature gauge on the top cap face, it allows riders and mechanics to instantly monitor real-time coolant temperatures without opening the hot pressurized system.

Features:

• Elevated Boiling Point: Increases operating pressure to 1.8 bar (26.1 psi) to raise coolant boiling point and prevent boil-overs during hard riding.

• Integrated Temperature Gauge: Top-mounted dial thermometer provides immediate visual coolant temperature monitoring in both Celsius and Fahrenheit.

• Prevents Coolant Loss: Stops pressure venting through the overflow hose, preserving fluid levels during low-speed, high-load technical trail sections.

• Heavy-Duty Spring & Seals: Constructed with high-grade stainless steel springs and durable silicone rubber seals to resist heat degradation and chemical corrosion.

• Direct OEM Fitment: Standard B-size cap dimensions drop directly onto radiator filler necks across major Japanese and European motorcycle models.

What's in the Box:

• 1x Twin Air 1.8 Bar Radiator Cap with Integrated Temperature Gauge (Part #177900)

Fitment Notes:

• Universal Standard Fitting: Fits most modern dirt bikes, dual-sports, and adventure motorcycles equipped with standard "B-Type" radiator filler necks (including KTM, Husqvarna, GASGAS, Honda, Yamaha, Kawasaki, and Suzuki).

• Clearance Notice: Verify overhead clearance between your radiator cap and aftermarket fuel tanks or oversized radiators prior to installation, as the integrated temperature gauge adds approximately 15mm in top height compared to flat stock caps.

• The Pressure Physics: Increasing system pressure does not make the engine run colder; instead, it expands the operational window before the fluid physically changes state from liquid to steam. Steam pockets inside a cylinder head create severe localized hot spots because gas transfers heat far less efficiently than liquid. Elevating the system pressure to 1.8 bar keeps the coolant liquid under extreme thermal spikes, preserving proper heat dissipation through the radiator cores.

  Cooling System Inspection: Before installing a 1.8 bar cap on an older motorcycle, inspect the condition of your radiator hoses, hose clamps, and water pump gaskets. Increasing system pressure from 1.1 bar to 1.8 bar places higher stress on the entire cooling circuit. Weak, dry-rotted hoses or loose worm-gear clamps may weep under the elevated pressure. Always install fresh hose clamps or inspect soft lines when upgrading to a high-pressure cap.

Part Number: 177900