Oil Drain Plug Crush Washers | Honda CT90 / CB100 / CB125 / CB500 / CB550 / CB750
Reusing a flattened crush washer is the fastest way to end up with oil on your garage floor. These aluminum sealing washers replace OEM 94109-12000 and give your drain plug a fresh, leak-free seal every oil change. Sold in a 5-pack so you always have spares in the toolbox.
Why You Need This
Crush washers do exactly what the name says — they crush once between the drain plug and the crankcase to form a tight seal. After a single use, the washer is compressed and loses its ability to seal properly. Reusing one risks a slow oil leak that gets worse over time, dripping onto your exhaust or pooling under the bike.
These are soft aluminum washers sized to fit the 12mm drain plugs used across a wide range of vintage Honda singles, twins, and fours — from the CT90 Trail 90 through the CB750 SOHC.
Specifications
| Spec | Detail |
|---|
| OEM Part Number | 94109-12000 |
| Material | Aluminum |
| Sold As | Pack of 5 |
| Fits Models | CT90 (1966–1978), CB100 (1970–1975), CL100 (1970–1973), SL100 (1970–1973), CB125S (1973–1978), CL125S (1973–1975), SL125 (1971–1973), CB500K (1971–1973), CB550K (1974–1978), CB550F (1975–1977), CB750K (1969–1978), CB750F (1975–1978), CB750A (1976–1978) |
Note: This washer fits Honda models using the 12mm drain plug (OEM 94109-12000). Honda CB350, CL350, CB360, and CB450 models use a different drain plug size and require a different washer.
Installation
Difficulty: Beginner
- Warm up the engine for a few minutes — warm oil drains faster and more completely.
- Place an oil catch container under the drain plug.
- Use a 6-point socket to loosen the drain plug — turn counterclockwise. A 6-point socket grips better than a 12-point and won't round the bolt head.
- Remove the drain plug and let the oil drain completely.
- Inspect the old crush washer. If it is flattened, cracked, or stuck to the crankcase mating surface, peel it off and discard it.
- Clean the drain plug threads and the mating surface on the crankcase.
- Place a new crush washer onto the drain plug.
- Thread the drain plug back in by hand to avoid cross-threading, then snug with a socket. Do not over-tighten.
Use a 6-point socket, not a 12-point. The soft metal on vintage Honda drain plug heads rounds easily with 12-point sockets — especially plugs that have been reused for decades.
Frequently Asked Questions
Do I really need to replace the crush washer every oil change?
Yes. Crush washers are designed for single use. Once compressed, the aluminum can no longer deform to create a proper seal. A new washer costs pennies compared to cleaning up an oil leak — or worse, running low on oil between checks.
Does this washer fit my CB350 or CB360?
No. The CB350, CL350, SL350, CB360, CL360, CJ360, CB450, and CB500T use a different size drain plug and require a different crush washer or O-ring. Check our CB350/CB450 drain plug or CB360 drain plug pages for the correct replacement.
What is the correct torque for the oil drain plug?
Torque varies by model. On the CT90, the Honda factory service manual specifies 2.0–3.5 kg·m (15–25 ft·lbs). For other models, consult your service manual. The key rule: snug but do not over-tighten. Stripping the threads in an aluminum crankcase is an expensive mistake.
Can I reuse a crush washer if it still looks okay?
Not recommended. Even if the washer looks intact, the aluminum has already taken a set from the previous tightening. A fresh washer ensures the seal compresses evenly and does not leak.
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Last updated: March 2026
