1901-1953 Indian Motorcycle – Parts – Accessories

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  5. Service Bulletin I-10 Oil Loss Through Crankcase Breather

Service Bulletin I-10 Oil Loss Through Crankcase Breather


When there is a noticeable amount of oil being lost out through the crankcase breather and the engine smokes out through the exhaust at 50 m.p.h. and over, there is too much oil in the crankcase.

There are four conditions that cause the crankcase to load up with oil and result in high oil consumption.

  1. A sump plug screen that is partially or totally clogged with foreign material.
  2. A sump plug that is loose or has a bad gasket surface.
  3. A pinion shaft seal that has worked out of the cam case cover.
  4. Rocker arm shaft screws that have too wide or deep a “flat” ground on them.

The above conditions can be corrected as follows:

  1. The sump plug may be removed and washed clean and replaced, making sure the gasket is in good condition and the surfaces on the crankcase and sump plug are flat and clean.
  2. A sump plug that is loose should be removed and washed clean. The surfaces and gasket must be inspected before reassembling and tightening. Any rough area on the crankcase or sump plug must be filed smooth and the gasket replaced if not in good condition.
  3. When the pinion shaft seal works out of the cam case cover, it will be necessary to press it back in place and stake or punch the aluminum around the edge of the seal to hold it firmly in place.
  4. When the rocker arm shaft screws allow too much oil to flow into the rocker boxes, it will be necessary to replace them with screws that measure according to the dimensions given (.277″ to .282″) in Service Bulletin I-1.
    NOTE: The “flat” shown in the sketch is exaggerated, so be sure to “mike” the screws.

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