| Also known as | E1591, MJ 1 1/8 C3 |
| Diagram | Fig. 2 — CRANKCASE · ref 29 |
| Subsystem | engine bottom |
| Listed in parts books | 1960–1962, 1964–1965, 1967–1974 |
MAIN BEARING,BALL C3 RHP 1 1/8 ID TRIUMPH CRANK T/S - D/S PRE 65 650
Ball-type crankshaft main bearing, 1 1/8 in ID, C3 clearance, used timing-side and drive-side on pre-'65 650 Triumph twins.
This is the ball-type main bearing that carries the crankshaft in the Triumph pre-unit and early unit 650 twins, listed in the parts book under the CRANKSHAFT AND CONNECTING RODS section. It's a 1 1/8 inch ID bearing in C3 clearance, used on both the timing side and drive side of the crank on the engines this catalog entry covers.
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The part shows up in our records under the modern number 70-1591, with the older factory forms E1591 and MJ 1 1/8 C3 referring to the same physical bearing. If you're working from an older parts book or a bearing marked up differently, those are the numbers to cross-check against.
Main bearings take the full load of the crank spinning inside the cases, so wear here shows up as play, noise, or oil pressure trouble at the mains. If you're splitting the cases for a rebuild this is a standard item to inspect and replace as a set rather than run on and hope.
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