DIY Network

Vintage-Motorcycle Maintenance: Exhaust Removal and Cam Gasket From "Weekend Mechanic" episode WKM-304

Bruce and his assistant begin work on a 1978 Yamaha motorcycle engine to repair a minor oil leak.

In this segment of Weekend Mechanic, the rusted exhaust pipes are removed in preparation of replacing them with new ones, and the valve-cover gasket is replaced in order to repair an engine-oil leak.

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.

Safety Alert: Always wear eye protection, and follow proper safety precautions, when working with power tools.

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, sparkplug wrench, putty knife, milliliter measuring cup, 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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Exhaust Removal

Later, we'll be installing a new muffler and set of exhaust pipes on the motorcycle. To prepare for that, and to also simplify some of the other scheduled maintenance we're performing, we went ahead and took off the old, rusted exhaust pipes.

• To remove the old exhaust pipes from the engine block, unscrew the three flange bolts where the three muffler pipes are attached to the engine block (figure A) Use caution when removing the exhaust pipe bolts as they may be difficult to get out, and they don't always come straight out of the engine block during removal.

• With bolts removed, carefully lift the exhaust pipes free (figure B).

  Figure A

  Figure B

  
  
• You'll need to remove the gas tank (figure C) in order access the valve-cover bolts.

• The valve cover is held in place with 21 Allen bolts. Remove all of the cam-cover bolts. They can be removed in any order.

• This is also a good time to remove the old spark plugs (figure D). Once the cam-cover is reinstalled, they will be replaced with new ones.

  Important: Only use a sparkplug wrench to remove old sparkplugs. A regular socket could break off the plug or damage the engine.

  Figure C

  Figure D

  
  

• With the cover removed (figure E), inspect the valve-cover gasket. In our case, it was evident that the worn gasket was the source of the oil leak (figure F).

  Figure E

  Figure F

  
  
• While the cover is removed, check the condition of the dual cam-shafts and timing chain (figure G). The chain should be adjusted about every 3000 miles, or when it becomes noisy. Our chain appears to be tight and in good shape.

• Using a standard putty knife to carefully loosen and remove the old gasket (figure H), then use the putty knife to remove any residue from the engine. Use caution to prevent gasket pieces or residue from falling down into the engine.

  Figure G

  Figure H

  
  
• Apply a small gasket sealer to the four corners of the mating surface at the top of the engine head (figure I) to help secure the gasket.

  Important: Sealer should not be used as a substitute for a gasket.

• Install the valve-cover new gasket (figure J).

  Figure I

  Figure J

  
  

  Figure K

• Set the cover back in place (figure K) and secure it with the bolts..

  Important: Check the position of the gasket before and after the cover is reinstalled, and before you tighten each bolt.

• With the cam-cover back on, install new sparkplugs.
  

Important: Included in this segment are the steps in this automotive procedure as shown in the episode. These steps are general guidelines that are applicable to most vehicles. With any particular vehicle, there may be procedures, specifications, settings, tolerances, components, etc. that are specific to that vehicle. There are also variations according to the type and brand of repair-kit you select. Always consult your vehicle's service manual when undertaking significant automotive repairs, and read and follow the manufacturer's directions and precautions that come with your kit or replacement parts.

RESOURCES :

The Complete Idiot's Guide to Motorcycles
ISBN: 0028624165
Author: editors of Motorcyclist magazine

The Haynes Small Engine Repair Manual
ISBN: 1850106665
Author: Curt Choate, John H. Haynes
Haynes Publishing Group