| Diagram | Fig. 3 — CYLINDER BLOCK – PISTONS – CRANKSHAFT · ref 16 |
| Subsystem | engine bottom |
| Listed in parts books | 1973 |
MAIN BEARING SET (4) 3CYL .020 USA
A set of four .020-undersize main bearings for the Triumph three-cylinder engine crankshaft.
Part number 70-9028 is a main bearing set for the three-cylinder Triumph engine, machined to .020 undersize for a re-ground crankshaft. The set comes as four bearings, matching the four main bearing journals on the triple's crank.
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If your crank has already been reground once and measured out at .020 under standard, this is the set that matches it. Standard-size and other undersize sets exist for the same crank, so before you order, get the actual journal measurements off your crank or the spec sheet from whoever did the regrind - ordering the wrong undersize means the bearings won't seat right and you'll be sending them back.
We don't have much more history on this one in our records beyond the basic listing, but the description is clear enough on what it is and what it's for. Call the shop if you want to talk through your crank's actual dimensions before you commit to this set.
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