06/08/2023
Owning a classic motorcycle like the 1967 Triumph Tiger Cub is a true joy, offering a tangible connection to motorcycling's rich heritage. However, keeping these vintage machines running smoothly requires diligent and correct maintenance, particularly when it comes to lubrication. Unlike modern bikes with their sophisticated, often integrated oil systems, classic Triumphs have distinct requirements for their engine and gearbox, and understanding these differences is paramount. Using the wrong type of oil or incorrect quantities can lead to premature wear, poor performance, and costly damage. This guide aims to demystify the oil requirements for your beloved Tiger Cub, ensuring it purrs along reliably for years to come.
Many Cub owners, especially those new to classic bike maintenance, find themselves scratching their heads over seemingly simple tasks like an oil change. Questions about oil capacity, the right viscosity, and the exact location of various drain and fill plugs are common. We'll cover everything from engine oil to gearbox lubrication, addressing common pitfalls and providing clear, actionable advice to help you maintain your Tiger Cub with confidence.
Understanding Your Tiger Cub's Lubrication Systems
The Triumph Tiger Cub, like many British motorcycles of its era, utilises two distinct lubrication systems: one for the engine and another for the gearbox and primary chaincase. It's crucial not to confuse these, as they require different quantities and sometimes different considerations for oil type.
Engine Oil: The Dry Sump System
Your Tiger Cub's engine operates on a 'dry sump' lubrication system. This means the engine's crankcase does not hold a large reservoir of oil. Instead, oil is stored in a separate oil tank, usually located under the seat or sometimes integrated into the frame. An oil pump circulates oil from this tank, through the engine, and then scavenges it back to the tank.
Engine Oil Capacity
For a 1967 Triumph Tiger Cub (T20 series), the engine oil tank typically holds approximately 2.5 pints (around 1.4 litres or 1400ml). It's always advisable to consult your specific model's workshop manual for the precise capacity, as minor variations could exist between years or specific variants like the Super Cub.
Recommended Engine Oil Type
For classic Triumph engines, the consensus among enthusiasts and experts leans heavily towards mineral-based oils. Modern synthetic oils, while excellent for contemporary engines, can sometimes cause issues in older designs, particularly with clutch slip due to their advanced friction modifiers, or seal degradation. A good quality 20W-50 mineral motorcycle oil is generally recommended. Look for oils specifically designed for motorcycles, often carrying a JASO MA or MA2 rating, which indicates suitability for wet clutches. Avoid car oils, as they often contain friction modifiers detrimental to motorcycle clutches.
Alternatively, some purists prefer a straight-grade SAE 30 or SAE 40 mineral oil, especially in warmer climates, mimicking the original specifications. However, a multi-grade 20W-50 offers better all-round protection across varying temperatures.
Checking and Changing Engine Oil
- Warm Up the Engine: Run the engine for a few minutes to warm the oil. This makes it thinner and helps drain more thoroughly.
- Locate the Drain Plug: The engine oil drain plug is typically a large bolt located at the lowest point of the engine sump plate, underneath the engine. Place a drain pan underneath.
- Drain the Oil: Carefully remove the drain plug. Be prepared for the oil to gush out. Allow ample time for all the oil to drain.
- Replace the Drain Plug: Once drained, clean the drain plug and its sealing washer (always replace the washer with a new copper or fibre one). Reinstall the plug, tightening it to the manufacturer's specified torque (do not overtighten).
- Refill with New Oil: Locate the oil tank filler cap (usually on top of the oil tank). Slowly add the recommended amount of new, correct-type oil.
- Check Level: After filling, start the engine and let it idle for a minute or two to circulate the oil. Then, shut it off and allow a few minutes for the oil to settle back into the tank. Check the oil level using the dipstick (if fitted) or by observing the level within the tank, ensuring it's between the 'min' and 'max' marks. Top up if necessary.
Gearbox Oil: Combined with Primary Chaincase
The Triumph Tiger Cub's gearbox and primary chaincase typically share the same oil. This means lubricating the gearbox also lubricates the primary chain and clutch. This system is separate from the engine's dry sump.
Gearbox Oil Capacity
The gearbox and primary chaincase together usually require approximately 1 pint (around 0.57 litres or 570ml) of oil. Again, confirm with your specific model's workshop manual.
Recommended Gearbox Oil Type
For the Tiger Cub gearbox, a good quality 20W-50 mineral motorcycle oil (JASO MA/MA2) is generally suitable, mirroring the engine oil. Some older manuals might suggest a straight SAE 30 or specific gear oil like EP90, but modern multi-grade motorcycle oils are often preferred for their availability and performance. Crucially, ensure it is not a modern car oil with friction modifiers that could cause clutch slip.
Understanding the Plugs: Drain, Fill, and Level
This is where confusion often arises, as illustrated by many new owners' experiences. The Tiger Cub gearbox has three key points for oil management:
- Drain Plug: Located at the very lowest point of the gearbox casing, directly underneath. This is for emptying the oil.
- Filler Plug: Usually located on the top or upper side of the gearbox casing. This is where you pour new oil in.
- Level Plug (or Overflow Bolt): This is a smaller bolt located on the lower side of the gearbox casing, often towards the front or middle. This is the critical plug for setting the correct oil level. When filling the gearbox, you remove this bolt, and oil is added through the filler plug until it just begins to weep or dribble out of the level plug hole. This indicates the correct fill level.
Changing Gearbox Oil Correctly
If you've encountered issues with overflow or using the wrong hole, don't worry, it's a common learning curve for classic bike maintenance. Here's the correct procedure:
- Warm Up the Bike: Take the bike for a short ride to warm the gearbox oil.
- Locate Drain Plug: Place a drain pan under the gearbox. Identify the drain plug at the very bottom of the gearbox casing.
- Drain Oil: Remove the drain plug. Allow all the old oil to drain completely.
- Replace Drain Plug: Clean the drain plug and fit a new sealing washer. Reinstall and tighten carefully.
- Locate Filler and Level Plugs: Identify the filler plug (top/upper side) and the level plug (lower side).
- Remove Level Plug: Remove the level plug first.
- Fill with New Oil: Slowly pour new oil into the filler hole. Continue pouring until oil just begins to seep or dribble out of the level plug hole. This ensures the correct quantity.
- Replace Plugs: Once oil weeps from the level hole, stop filling. Replace the level plug (with a new washer) and then the filler plug (with a new washer). Tighten both to spec.
- Check for Leaks: Run the engine briefly and check for any leaks around the plugs.
Addressing Common Mistakes
The scenario described by many owners – where oil overflows from the top while the 'overflow bolt' is out and nothing comes out – points to a common error: using the wrong fill point. If you've removed the gearbox level plug (the 'overflow bolt') but are pouring oil into a different hole, like the primary chaincase inspection cover or even the engine oil filler, then the gearbox won't fill correctly, and the oil will indeed overflow from the incorrect top hole. Always ensure you are pouring into the specific gearbox filler plug.
If you've used 20W-50 engine oil for your gearbox, and it's a motorcycle-specific mineral oil with a JASO MA/MA2 rating, then it's likely suitable. However, if it was a car engine oil, it might contain friction modifiers that could lead to clutch slip. In such a case, it's best to drain it and refill with appropriate motorcycle-specific oil.
Mineral vs. Synthetic Oil for Your Cub
The question of synthetic oil often arises, and for classic motorcycles like the Tiger Cub, the answer is generally to stick with mineral oil. Here's why:
- Clutch Compatibility: Most modern synthetic oils contain friction modifiers designed to improve fuel economy in cars. These additives can cause the wet clutches in older motorcycles to slip, leading to poor power transfer and premature wear. Mineral oils, especially those rated JASO MA/MA2, are formulated to be compatible with wet clutches.
- Seal Compatibility: Older engine seals (often made of cork, paper, or specific rubber compounds) were not designed to withstand the more aggressive detergents and chemical compositions of synthetic oils. Synthetics can sometimes cause these older seals to shrink, harden, or leak.
- Engine Tolerances: Vintage engines were built with looser tolerances than modern engines. Mineral oils, with their slightly thicker film strength, are often better suited to these tolerances and can help cushion moving parts more effectively.
- Cost: Mineral oil is generally more affordable, and given the frequent oil change intervals recommended for classic bikes, this can add up.
While some highly specialised synthetics exist for classic bikes, they are rare and expensive. For the vast majority of Tiger Cub owners, a good quality mineral 20W-50 motorcycle oil is the safest and most effective choice.
Comparative Overview: Engine vs. Gearbox Oil
To summarise the key differences, here's a comparative table:
| Feature | Engine Oil (Dry Sump) | Gearbox Oil (Wet Sump) |
|---|---|---|
| Primary Function | Lubricates engine components (crank, piston, valves) | Lubricates gears, shafts, and primary chain/clutch |
| Capacity (Approx.) | 2.5 pints (1.4 litres) | 1 pint (0.57 litres) |
| Recommended Type | 20W-50 Mineral Motorcycle Oil (JASO MA/MA2) | 20W-50 Mineral Motorcycle Oil (JASO MA/MA2) |
| Drain Plug Location | Under engine sump plate | Under gearbox casing |
| Fill Point Location | Oil tank filler (under seat/on frame) | Top/upper side of gearbox casing |
| Level Check Method | Dipstick on oil tank, or visual check in tank | Via level plug on lower side of gearbox casing |
| Change Interval | Every 1,000-2,000 miles or annually | Every 2,000-3,000 miles or annually |
Frequently Asked Questions (FAQs)
How often should I change the oil in my Tiger Cub?
For both engine and gearbox, it's generally recommended to change the oil every 1,000 to 2,000 miles, or at least once a year, whichever comes first. Even if the mileage is low, oil degrades over time and absorbs moisture, so annual changes are crucial for classic bikes.
Can I mix different types of oil?
It's strongly advised against mixing different types or brands of oil, especially mineral and synthetic. Different additive packages can react negatively, reducing lubrication effectiveness and potentially causing sludge or foaming. Always drain completely and refill with a single, consistent type and brand.
What if I overfill the oil?
Overfilling the engine oil can lead to excessive crankcase pressure, seal leaks, and oil being forced into the air filter or exhaust. Overfilling the gearbox can cause excessive drag, foaming, and potentially blow seals. If you've overfilled, it's best to drain the excess until the correct level is achieved. For the gearbox, simply remove the level plug and let the excess drain out.
Where exactly are the plugs on my Cub?
While locations can vary slightly, for a typical T20 Tiger Cub:
- Engine Drain: Look directly under the engine crankcase, usually a large hexagonal bolt on the very bottom.
- Engine Fill: Follow the oil line from the engine to the separate oil tank. The filler cap will be on top of this tank.
- Gearbox Drain: At the absolute lowest point of the gearbox casing, beneath the bike's left footpeg area.
- Gearbox Fill: On the top of the gearbox casting, often a large slotted or hexagonal plug.
- Gearbox Level: On the side of the gearbox casing, typically a smaller bolt located about halfway up the casing, or slightly lower. This is the one you remove to let excess oil weep out.
Why is my clutch slipping after an oil change?
If your clutch starts slipping after an oil change, the most common culprit is using an incorrect oil type, specifically a modern car engine oil containing friction modifiers (e.g., 'energy-saving' or 'fuel-efficient' oils). These additives reduce friction too much for a wet clutch system. The solution is to drain the oil immediately and refill with a motorcycle-specific mineral oil with a JASO MA or MA2 rating.
Conclusion
Proper oil maintenance is the cornerstone of keeping your 1967 Triumph Tiger Cub running reliably and preserving its mechanical integrity. By understanding the distinct needs of its engine and gearbox, using the correct types and quantities of oil, and diligently following the right procedures, you can avoid common pitfalls and ensure your classic British motorcycle continues to provide many miles of enjoyable riding. Always refer to your bike's specific workshop manual for the most accurate information, and if in doubt, consult with a reputable classic motorcycle mechanic. Happy riding!
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