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 – Suzuki M109R Rear Diff Fluid Change


Klotz transmission oil

Honda contact brake cleaner


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

Suzuki M190 rear diff oil change

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. 

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. 

Suzuki Boulevard M190 drive fluid change

NOTE: Wear safety glasses for this, since contact cleaner can harm your eyes. 

The steps for changing the final drive fluid are the same or similar for all Suzuki motorcycles. However, if you want to see a final drive change on a similar Suzuki mode, watch the video above to see how to change the final drive oil in a Suzuki M90 Boulevard


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