How to Change Drive Fluid on a Suzuki M109

Drive train or final drive fluid changes are an often-overlooked, yet crucial motorcycle maintenance task. 

Changing the drive train fluid on a Suzuki motorcycle takes only a handful of minutes. Watch the video above and follow the step-by-step guide below to change the final drive fluid on a Suzuki Boulevard M109 motorcycle.

NOTE: This process applies to both Suzuki Boulevard and Suzuki Boss models.

Tools and Supplies Needed – Suzuki M109R Rear Diff Fluid Change


  • 3/8th ratchet
  • 21mm socket
  • 17mm socket

Changing the Rear Differential Fluid on a Suzuki M109

Step 1. Get a drain pan ready, and remove the 21mm drain bolt on the rear differential. 

Suzuki M-109 Boulevard final drive oil change

Step 2. Replace the drain bolt once the fluid is completely drained, and torque it to 16.5 foot-pounds. 

NOTE: This bolt has a crush washer that needs to be replaced if it’s damaged.

Step 3. Remove the 17mm fill bolt. 

Suzuki Boulevard drive oil change

Step 4. Fill the rear diff with fresh 80W90 hypoid gear oil

NOTE: Add about 7.4 ounces, which should be just about when fluid starts running out of the fill opening. You’ll know you’ve added enough when that happens. 

Suzuki M190 rear diff oil change

Step 5. Wipe the excess fluid off and replace the fill bolt. Snug it down without overtightening it. Use contact cleaner to clean any overspill off of the motorcycle’s surfaces and you’re done. 

NOTE: Be sure to wear safety glasses for this, since contact cleaner can harm your eyes. 

Suzuki Boulevard M190 drive fluid change

Stay tuned to the Partzilla blog for more repair and how-to articles and videos about Suzuki motorcycles, and other motorcycle and ATV makes and models. 

Ready to buy parts for your Suzuki motorcycle? Select your bike’s year, make and model and find the OEM Suzuki parts you need at the lowest prices available online right here at!


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