| Diagram | Fig. 9 — CLUTCH AND PRIMARY CHAINCASE · ref 8 |
| Subsystem | primary |
| Listed in parts books | 1969–1972 |
BSA Tensioner — primary chain
Primary chain tensioner for the clutch/primary chaincase, keeps slack out of the primary drive chain.
70-8310 is a primary chain tensioner, the piece that takes up slack in the primary chain running between the engine sprocket and the clutch inside the primary chaincase. It shows up in the catalog under the clutch and primary cover figures, which is where you'd expect it — the tensioner sits low in the chaincase where it can bear against the chain run.
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Our catalog records tie this part to figures spanning 1969 through 1972 appearances, but the description on file doesn't name a specific model. The listing title elsewhere ties it to the A65, which points toward BSA rather than Triumph despite how it's filed in our system.
If you're rebuilding a primary chaincase and need to know whether this tensioner matches what's currently in there, give us a call before you order — we can confirm against what your bike's chaincase actually takes.
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