Hyper Bee service guide
The short answer: use 50 mL (50 cc) of 10W-40 oil meeting API SN or higher. That is the specification printed in the Sur-Ron Hyper Bee Owner's Manual.
What the diagram means
The factory procedure says to work with the gearbox cold and the key off, remove port screw A, drain the old oil, tilt the bike to the right, add 50 mL through the same opening, and reinstall the screw.
The opening is low on the reduction case. In shop practice, a low port like this can also let excess oil escape when the gearbox is returned to level. That “let it settle until it stops dripping” method is useful practical guidance, but it is not stated as the factory measuring method; the factory instruction is to measure 50 mL.
Why ordinary oil works
Wet-clutch motorcycles can be sensitive to friction modifiers because the engine oil also controls clutch-plate friction. The Hyper Bee reduction gearbox contains gears and bearings, not an oil-bathed clutch, so that clutch-specific concern does not apply here.
A normal, quality 10W-40 meeting API SN or higher is the straightforward choice. You do not need an exotic racing oil. Despite the word “gearbox,” do not assume thick 75W-90 automotive gear oil is equivalent—the viscosity grading system and formulation are different.
At the modest operating temperature and load of this small reduction stage, 10W-30 will still create a lubricating film and is a reasonable temporary substitute if that is what you have. It is practical guidance, not the printed factory specification.
Clean, simple fill method
A brake-bleeding kit is an inexpensive way to get a 50–100 mL syringe plus a short length of hose. Use a new or thoroughly clean syringe—never introduce brake fluid or dirt into the gearbox.
Key the bike off and stabilize it on a lift stand. Put a drain container below port A.
Remove screw A and allow the old oil to drain until it is only dripping intermittently. Inspect the screw, sealing surface and drained oil.
Remember that 50 cc and 50 mL are the same volume. Draw the oil into the syringe, attach the hose and keep both clean.
Follow the manual by tilting the bike to the right and injecting the measured oil. A small clean funnel with a hose also works if a syringe is unavailable.
The manual specifies 20–25 N·m. Start the screw by hand, confirm the seal is seated and use a torque wrench when possible.
If too much oil was poured in, return the cold gearbox to level over the container and allow excess at the open port to settle to an occasional drip before reinstalling the screw. This is EMR practical guidance; measuring 50 mL remains the factory method.
Underfilling leaves less oil available to separate loaded metal surfaces. That can increase noise, temperature and long-term gear or bearing wear.
Overfilling can make rotating parts churn through excess oil, adding drag and heat. Pressure can encourage seepage at a seal, although a small accidental overfill does not guarantee seal damage.
Hyper Bee oil FAQ
The gearbox is forgiving compared with a shared-engine-oil wet clutch, but oil still needs suitable viscosity, additives and material compatibility. Use the specified 10W-40 API SN or higher when you can. The point is that an expensive motorcycle-specific wet-clutch oil is not required.
Use the manual's 10W-40 engine-oil specification. A 75W-90 gear-oil label uses a different viscosity scale and may be considerably thicker; “gearbox” does not automatically mean automotive differential oil.
PDF page 27, section 10.1, lists 10W-40 API SN or higher and 50 mL. PDF page 35, section 10.18, shows port A and the replacement steps.
Send Electric Moto Garage a clear photo of the motor/gearbox side and your model year. Parts inquiries are normally answered within a few hours, as soon as possible.
Parts, measurements and diagrams
EMR can help with factory part numbers, bolt sizes, exploded diagrams and parts shipped by air from Sur-Ron China to your doorstep.