Changing the Gearbox Oil on a 2-Stroke Motorcycle

[EuropeanNC30R...]

Background

As you may know, the gearbox oil on a 2-stroke is completely separate from the top-end of the engine where the combustion takes place. The gearbox oil lubricates the clutch and gearbox.

This part of the engine is known as the 'bottom-end', and is designed to be lubricated by a 4-stroke engine oil, it is not a total-loss lubrication system like the 'top-end'. This means that it shouldn't need to be topped up; it should be changed instead.

If you do find the gearbox oil level is going down it implies that a seal(s) is damaged and you have a leak.

It's difficult to say how often you should change the gearbox oil, but you should definitely aim to do it as least as often as the manual states. I tend to change mine every 1500-1800 miles to keep the gearchange action sweet, but then my gearbox is very stiff.

Which Oil to Use?

The 4-stroke oil you need to use depends on your machine. My bike's workshop manual states SAE10/40W(yours may well be different), and to use a good quality oil. It's always best to use the highest quality oil you can afford, especially if you have a highly tuned 2-stroke.

Personally I use Putoline fully synthetic. Keep In mind 2-strokes only need a small amount of gearbox oil, usually less than a litre, so it's a false economy using £2/litre oil.

Never use car engine oil. It may be the right viscosity and it may be a quality oil, but car oil is not designed to lubricate the clutch. Because of this it contains special additives that aid car gearbox lubrication; these special additives cause motorcycle clutches to slip.

How To Change It

Before you start, you need :-
1. The correct amount and type of gearbox oil.
2. An oil-drain container, to catch the oil as it falls out. This could be anything from a washing up bowl to an old oil bottle/container with the side cut out.
3. Some newspaper so you don't stain the floor when you miss the oil-drain container.
4. The correct size spanner/socket for the oil-drain bolt, mine is 15mm.
5. You also might need some pliers if the filler cap is too stiff to undo by hand.
6. A mate to hold the bike upright is also handy, but not vital.
7. A funnel.

The first thing to do is to start the bike up and let it run for a few minutes, take it round the block if you fancy. This warms the oil up so it runs out a lot quicker and there is less chance of some old oil staying in.

Next put the bike on its side-stand. It's best not to use a Paddock Stand as it pivots the bike forward - this will give an inaccurate sight glass reading when you come to refill the oil.

Now undo the filler cap. The filler cap on my bikes have been on the right hand side, you should see a drain bolt somewhere underneath and usually an oil-capacity plate on the gearbox(If in doubt consult your manual or the net).

Position your oil-drain container to catch the oil coming out of the drain hole and place the newspaper underneath and around.

It's time to undo the drain bolt, try not to get oil all over your hand , and put the bolt somewhere safe. The oil should be pouring out now; it shouldn't take more than a few minutes to empty. When it starts trickling lean the bike from side to side to get the last drops out.

When its finished replace the drain bolt and dispose of the used oil safely . Some bikes also have a little bolt near the filler cap that you undo; on filling you can tell when you have the right amount of oil when it starts running out of here. On most other bikes there is a sight glass.

Now measure out the right amount of new gearbox oil and pour gently through the funnel into the filler-hole. Remember to keep checking the sight glass etc incase there was some oil remaining.
Though it's always better to have a slight touch more than not enough.

Once all the oil is in check the sightglass with the bike upright, if there isn't enough add a little more until there is. Replace the filler cap (and sight bolt if necessary) and you're finished - Well Done! [/i]