Changing the shaft drive oil on a Suzuki Boulevard C50 or M50 is even easier than changing the engine oil, so why did it take me years to learn how to do it?

I’ve owned a couple of Suzuki Boulevard M50s. In fact, I’ve even previously written about how to change the oil on a Suzuki Boulevard M50. For years I felt confident changing my oil and filter on the M50, after all, everything was within eyesight, but that final gear oil, or shaft drive oil? That was scary and mysterious stuff. Which is kind of silly, because changing the drive shaft oil is even easier!

Oh, before I get too far ahead of myself,, don’t worry, the two bikes use the same motor, so this applies to you too.

There’s really nothing to changing the shaft drive oil or final gear oil on one of these Suzuki Boulevards, but it’s something that you should do every 12,000 km (7,500 miles) or at least every two years for those that aren’t riding much.

Sure, you could not change your final gear oil, but neglecting your drive shaft oil can cause increased wear on the gears and bearings causing excess noise and vibration and total mechanical failure. Considering we can change this oil in a couple minutes with just a wrench, doing the work is a no-brainer.

What you’ll need

200 to 220 mL of SAE 90 hypoid gear oil with GL-5 under API classification. I use this one from Bel-Ray for the right combination of price and quality, and an easy to use spout.

I use this one from Bel-Ray for the right combination of price and quality, and an easy to use spout. A wrench. Even a cheap one from the dollar store will be good enough, but don’t buy tools from the dollar store unless you have no other choice.

Instructions

All work should be done on a warm motorcycle that is perfectly upright. Not a cold bike. Not a hot bike. Not a bike on it’s side stand. A warm bike that is upright. Now that that’s clear…

Step 1: With a warm bike, locate and remove the final gear oil drain plug

To locate the final gear oil drain plug on a Suzuki Boulevard M50 or Suzuki Boulevard C50, look at the axle that goes through the center of the back tire. Now look a couple of inches under it, on the left side of the bike. See that drain bolt down there? That’s what you want.

Before you loosen that off, you’ll want to have a plan for how to catch the oil that falls, otherwise it’s going to get all over your rear tire, and that could cause you to slip and crash. So figure out something to catch the oil, and you can even use a piece of card board or a plastic bag to protect your rear tire if you want.

Now that you’ve located the drain plug and your tire is safe, loosen that plug off.

Step 2: Clean up the drain plug

The final gear drain plug (shaft drive drain plug) on a Suzuki Boulevard M50 is magnetic, from factory, which is great. You’ll see all kinds of debris attached to your drain plug. Wipe it up carefully. What you’re seeing is little metal shavings from natural wear inside of your motorcycle. But leaving those metal shavings in there could hurt your bike, so clean up that plug!

Step 3: Open the filler cap

Remember your rear tire axle? On the left side of the bike, just behind it, is your filler cap. Take a wrench to it to remove that.

Step 4: Replace drain plug and refill

Once your oil is done slowly dripping out, put your drain plug back in place. The service manual doesn’t give a torque specification for this plug, so just try to get it tight, but not so tight that you risk stripping it. No need to go He-Man on this thing. Less is more.

The service manual says to pour the recommended oil in through the filler hole until the oil level reaches the filler hole. Meaning you can pretty much pour it in until it just starts to overflow.

The service manual estimates that the bike needs about 200-220 ml of gear oil, however manufacturers only sell them in litres or quarts, so if you have a friend with a shaft drive bike, now’s a good time to invite him/her over to share.

Step 5: Put the lid back on and go for a ride.

Conclusions

When you’re done, put the cap back on and go for a ride.

I don’t know why, for years, I shied away from servicing my drive shaft myself. There’s no filter to worry about, so little fluid (meaning so little potential for mess), and you can do it all with just a hand wrench. It’s even easier than an oil change.

12/10, strongly recommend doing your shaft drive oil change / final gear oil change yourself.