AMSOIL 100% Synthetic Dirt Bike Transmission Fluid

Product overview

A dirt bike with a separate transmission sump asks one fluid to protect the gears and run the wet clutch, and it does that while the engine sits at high rpm in dirt and heat. AMSOIL Synthetic Dirt Bike Transmission Fluid is formulated for that shared job.

It belongs only in bikes with a separate gearbox sump. If the engine and transmission share oil, the bike needs a motorcycle oil instead.

What the formula does

• Wet-clutch compatible and free of friction modifiers, so clutch feel stays consistent on takeoffs and through obstacles.
• The lower viscosity gives a more aggressive clutch feel.
• Synthetic base oils resist thinning out under hard use and protect gears and clutch plates.

Where this fluid fits

Use in two-stroke and four-stroke dirt bikes that use a separate transmission sump, including bikes made by:

• Honda
• Yamaha
• Kawasaki
• Suzuki
• Husqvarna
• KTM

Why a dirt bike gearbox calls for JASO MA

A dirt bike that runs a separate transmission sump asks one fluid to lubricate the gear set and to carry the wet clutch at the same time. That combined job is what the JASO MA specification describes, and AMSOIL Synthetic Dirt Bike Transmission Fluid is formulated for two-stroke and four-stroke bikes whose separate sump calls for it, including machines built by Honda, Yamaha, Kawasaki, Suzuki, Husqvarna, and KTM.

A passenger-car motor oil is the wrong choice in that sump. Those oils carry friction modifiers meant to cut drag inside an engine, and once those additives reach the clutch plates they can cause a wet clutch to slip. This formula is friction-modifier-free, which is why clutch take-up stays predictable instead of going soft partway through a ride.

Clutch feel on launches and through obstacles

Friction durability is the property that keeps a clutch feeling the same on the last lap as it did on the first. Synthetic Dirt Bike Transmission Fluid is built to help eliminate clutch slippage, fade, and chatter, so engagement stays consistent during launches and while a rider is picking a line over and around obstacles.

The formula sits on the light side at 10.3 cSt at 100°C, and the lower viscosity is deliberate: it delivers a more aggressive clutch feel than a heavier gearbox oil. That trade is worth knowing about before a rider switches away from a thicker fluid.

Holding viscosity through a long moto

The constant engagement of metal parts inside a dirt bike transmission can break an ordinary lubricant down and let it thin out. Once a transmission fluid drops below its intended viscosity range, it can no longer hold a strong film between the parts, and wear follows.

The synthetic base oils in this fluid resist that thinning and keep a thick protective film in place, even under heavy clutch use in extreme conditions. Premium anti-wear additives add a second layer of protection that helps extend gear and clutch life, and a viscosity index of 144 describes how steadily the fluid holds its thickness as the gearbox heats up.

Matching the fluid to the right powersports gearbox

Powersports gearboxes are not interchangeable, and neither are the fluids that serve them. A V-twin motorcycle transmission runs a much heavier oil at 20.7 cSt at 100°C and takes AMSOIL Synthetic V-Twin Transmission Fluid instead, while an ATV or UTV gear case takes ATV/UTV Transmission and Differential Fluid.

Change intervals follow the vehicle manufacturer's recommendations rather than a fixed mileage number, because an enduro bike and a weekend trail bike accumulate hours very differently. Confirming the gearbox drain schedule in the owner's manual is the last step before ordering.

Specifications Dirt Bike Transmission Fluid covers

This fluid covers dirt bike transmissions that require the following:

• JASO MA

Coverage as published in the AMSOIL data bulletin, checked July 2026. AMSOIL revises coverage when a formula changes, so confirm against AMSOIL's current data bulletin before ordering.

Service life

Change according to the vehicle manufacturer's recommendations.

Typical technical properties

Typical properties published by AMSOIL, checked July 2026. These are representative values rather than a specification, and they change when AMSOIL updates a formula.

Package sizes and product codes

Select a product code to open that package size on the AMSOIL product page.

Product documents

AMSOIL publishes the full technical detail for this product in these documents.

• Dirt Bike Transmission Fluid product data bulletin (PDF)
• Dirt Bike Transmission Fluid safety data sheet (PDF)

Where to order

Confirm this formula is the match for the vehicle or equipment in the AMSOIL product guides, then order Dirt Bike Transmission Fluid online. Existing members can sign in to apply the discount automatically.

Details and questions