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Vintage-Motorcycle Maintenance: Changing Fluids From "Weekend Mechanic" episode WKM-304

Bruce and his assistant remove the front wheel in order to send it out for tire replacement.

In this segment, Weekend Mechanic host Bruce Bonebrake continues work on a 1978 Yamaha motorcycle. As part of the routine maintenance being performed, the engine oil and gear-case oil are changed. Changing fluids frequently is often the key to a great-running motorcycle.

DIY Difficulty Rating for Repair: The repairs and service included here are fairly routine, and most can be found in the motorcycle's service manual. We gave it a difficulty rating of 2 on a 5-point intermediate-level scale. It took us about 8 hours, spread over two days, to complete the job.

Materials:

In addition to standard auto-mechanic's shop tools (wrenches, ratchets, extenders, screwdrivers, nut-drivers, etc.), some of the specialty tools that will be needed for this project include a motorcycle work bench, hydraulic brake-bleeder pump, torque wrench, milliliter measuring cup, drain pan and a motorcycle jack.

An air-compressor and set of pneumatic tools is optional, but may help speed the repair and maintenance process.

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Changing Fluids

• We began by removing the drain plug on the final-gear case (figure A) to replace the gear oil. The hypoid gear oil that was drained out was very dirty and thick.

  Important: Never substituted ordinary motor oil for hypoid gear oil.

• Next, remove the fill plug from the upper part of the final-gear case (figure B).

  Figure A

  Figure B

  
  
• The motorcycle uses about 350 ml of hypoid gear oil. Pour the oil into a milliliter measuring cup (figure C)

• Replace the drain plug, and carefully pour the oil into the fill opening (figure D).

  Figure C

  Figure D

  
  
• Check to ensure the proper fill level using the short end of the dip stick as shown (figure E).

• Once the level checks out, replace the fill plug and tighten it down (figure F).

  Figure E

  Figure F

  
  
• Next, we replace the oil in the center gear case. Loosen and remove the plug at the lower end of the center-gear case (figure G), and drain out the old fluid.

• Note that the gear-case plug (figure H) has a magnetic tip. This aids in trapping metal particles that may contaminate the oil and could cause damage. If there are large metal particles visible on the magnet, or an inordinately large amount, you may want to consult with a professional motorcycle technician.

• Important: Gear oil should be changed every 10,000 to 12,000 miles.

  Figure G

  Figure H

  
  
  
  

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  ALSO IN THIS EPISODE:
  	Vintage-Motorcycle Maintenance: Removing the Wheel and Seat-Cover
  	Vintage-Motorcycle Maintenance: Exhaust Removal and Cam Gasket
  	Vintage-Motorcycle Maintenance: Changing Fluids
  	Vintage Motorcycle Maintenance: Oil & Filters Change, Exhaust and Brakes