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Assembling the Crankcases

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Written by Randy Fox   
Saturday, 03 November 2007

Closing the Cases

Now the cases must be prepared for final closure. Your case should now look like the photo below.

 

Crankcase, right, open, empty, Yamaha Road Star

 

Be sure the gasket surfaces of both the left and right crankcases are free of oil, dirt, and fingerprints. Tip: To be certain, I cleaned mine with xylene on a clean rag. Or you can just use paint thinner on a clean rag, if you let it completely dry before continuing.

Take photos.

Apply Yamabond to the entire mating (gasket) surfaces of the right-side crankcase--including the little ‘V’ part between where the cylinders go.

 

Yamabond Tip 1:

I used four, new, 1"-wide, parts cleaning brushes (aka chip brushes). See photo below. I cut the bristles to half-length for better control. Then I trimmed off about 1/3rd of the bristles on each brush to make them thinner.

 

Crankcase, gasket brush, Yamaha Road Star

 

Yamabond Tip 2:

I also used a plastic lid as a ‘painter's pallet,’ and squeezed a glob of Yamabond on to the lid.

Although the Yamabond must be applied thinly, be sure to cover the surface well. After about 25% of my gasket was painted, the Yamabond began to thicken on the brush, so I tossed it, squeezed a new glob of Yamabond on a new area of my plastic lid, and continued--using a fresh brush.

 

Yamabond Tip 3:

I had been told to use a very thin coat of Yamabond--so I did. But I also made sure I got complete coverage.

I don't recommend using a thicker layer at certain places, as that would make for uneven gasket formation. Also, I don't recommend laying down two coats, as that would make the gasket too thick, and possibility allow too much end-play in all the shafts. Just be sure you paint on a full-coverage gasket.

 

Yamabond Tip 4:

Work quickly, but don't rush. You have about 15 or 20 minutes of working time, if using Yamabond-4.

 

 

Alignment Dowel Tip: I lube all alignment dowels when I insert them. That way, they aren't likely to hang up or jam while closing the cover over them. This also acts like a 'glue,' to hold the dowel. And I figure, a film of assembly lube trapped in with the dowel, will inhibit rusting.

Lube and re-insert two alignment dowels into the right-side case.

Be sure the last bit of Yamabond you painted on has had enough time to skin over--usually about a minute. Then carefully place the left-side case onto the right-side case. As you do this, watch the transmission shift-drum-assembly. It might need a bit of rotating, to align with the (puzzle piece) hole pattern in the left-side case.

Now press down, being sure all shafts fully seat without binding, especially for the transmission. Remember, you will need to use a bit of extra pressure to seat the little O-ring for the crossover tube, but do not force the fit.

Check that all shafts rotate freely, without excess end-play. Also check that the cases are fully seated.

Bolt on and torque the 15, M6, left-side case bolts (7.2 ft-lbs). Tip: Be sure you remember the long one that goes in the recess of the shift-shaft area, away from the case perimeter.

Then tip the engine up, and install/torque the six right-side ones (17 ft-lbs for the three M8 bolts, and 7.2 ft-lbs for the three M6 bolts). Refer to the service manual.

 

Image

 

Take picts.

Stuff some rags in the case holes around the connecting rods. Tip: Instead, I used some small food containers with cut-outs for the rods. This protects the cases from the rods, and prevents parts, tools, and dirt from falling in. Similarly, stuff rags into the lifter-block holes and cam area. See photo below.

 

Image

 

Bolt up all sight plugs and drain plugs in the cases. Use 5 to 6 lb-ft of torque on the little sight plugs. Be sure to use copper or plastic washers under each. Drain plugs are torqued to 31 ft-lbs.

Loosely thread in the left-side case bolt for the chrome, ‘Y’ shaped, oil-delivery tube. It is near the generator shaft cover area. This is just to keep dirt and tiny parts from dropping in during assembly.

Take picts.

 
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