HOW TO CHANGE MOTORCYCLE TRANSMISSION OIL

How to change gear oil in your motorcycle

If you read motorcycle maintenance forums, this is a subject that causes a lot of controversy. New riders are often surprised that the transmission generally uses the same oil as the engine. So the good news is that for most motorcyclists, once you've changed your engine oil, you've changed your transmission oil too.

Exceptions to this rule most often come in the shape of classic motorcycles from brands like Triumph, Harley-Davidson and Buell. These bikes are most commonly of a 'pre-unit' construction, meaning that their transmissions also need regular oil changes.

Your manual will tell you if this is the case, and you can also use Castrol's  quick and easy Oil Selector tool to find out if you need separate gearbox oil, and if so, which specification you need.

Once you've bought the appropriate transmission oil, you'll need an oil drain tray, a long-necked funnel, a set of Allen keys and a torque wrench. We also recommend that you wear disposable latex gloves to protect your skin from the irritation that oil can sometimes cause.

It's good to have warmed the bike up a little before you start the oil change, as warm oil will drain out of the transmission more effectively. Once you've done that, park your motorcycle on level ground, using its centerstand or a paddock stand.

Then locate the oil drain plug, which is underneath the bike and between the shock absorbers, then place your oil drain tray underneath.

Next, remove the fill plug at the top of the gearbox with a wrench and place this somewhere safe. Now you're ready to remove the drain plug, using an Allen key. This will usually be an 8mm Allen key.

While the oil runs into the drain tray, it's a good idea to wipe off the drain plug with a rag before putting it somewhere safe; as the built-in magnet most probably has a small amount of metal filings attached, and you don't want to re-introduce these to your transmission.

You should also check the 'O' ring on the drain plug, and replace it if it shows any signs of wear or cracking.

Once the old oil has drained away, smear a little oil on the 'O' ring, replace the drain plug, and tighten with a torque wrench. The setting for this is usually about 15-17 pounds, but always check with your motorcycle's manual to make sure you get this right.

You're now ready to add the transmission oil specified by the OEM, by slowly and carefully adding it through the funnel. Once that's done, simply replace the filler cap using your torque wrench, wipe away any excess oil that may have splashed or spilled, and you're ready to ride again.

Importantly, you should make sure that there's no leakage from either the fill or drain hole, and remember to check again once you've been for a ride, to ensure that your transmission maintains the right level of oil at all times.