| Also known as | E5977 |
| Diagram | Fig. 9 — OUTER PRIMARY COVER – CHAIN TENSIONER – CLUTCH CONTROL · ref 33 |
| Subsystem | primary |
| Listed in parts books | 1966–1973 |
TRUNNION PRIMARY TENSIONER
The pivot trunnion for the primary chain tensioner blade, letting it move to take up chain slack inside the chaincase.
70-5977 is the trunnion for the primary chain tensioner blade. It's the small pivot piece that lets the tensioner blade move and take up slack in the primary chain as it wears, keeping the blade riding correctly against the chain instead of binding or slopping around inside the chaincase. This part number shows up across the outer primary cover, chaincase, and primary transmission figures, so it's tied into whichever tensioner blade and adjuster setup your primary case uses.
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The older book reference for this part is E5977, which you may run across if you're working from an earlier parts list. Given how many years and figure listings this one appears in, it's clearly a long-running design rather than something specific to one narrow production run.
It's a small, inexpensive item to have on hand, and worth checking against your existing tensioner blade before ordering since trunnions and blades need to mate up correctly to do their job.
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