| Diagram | Fig. 2 — CRANKCASE · ref 11 |
| Subsystem | engine bottom |
| Listed in parts books | 1976–1977, 1979–1980, 1983, 1985 |
Hollow dowel, crankcase joint
Hollow locating dowel used at the crankcase joint to align the case halves before assembly.
This is a hollow dowel that fits into the crankcase joint, part number 71-3989. Its job is to line up the crankcase halves precisely before the main fasteners are drawn down, so the mating faces seat square and the joint stays true. It's a small part, but if it's missing, worn, or the wrong size, you can end up with a case that won't seal right no matter how much sealant you throw at it.
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The catalog shows this dowel appearing in crankcase-related listings from the mid-1970s into the mid-1980s, which lines up with the later unit-construction twins in that era. Beyond that, our records don't spell out an exact model or year, so if you're matching this to a specific engine, check the fit before you button the cases back up.
It's cheap enough to just keep a couple of spares in the drawer for whenever you've got a crankcase split open, since these are easy to lose track of in the parts tray during a rebuild.
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