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BSA pre-unit twin bore & stroke data |
ID |
Type |
Size, CC |
Bore, MM |
Bore, inches |
Stroke, MM |
Stroke, inches |
Rod, inches |
Rod, MM |
Rod ratio |
4K
P-speed |
1 | A7 early | 495 | 62 | 2.441 | 82 | 3.228 | 6.500 | 165.1 | 2.013:1 | 7,435 |
2 | A7 late | 497 | 66 | 2.598 | 72.6 | 2.858 | 6.000 | 152.4 | 2.099:1 | 8,397 |
3 | A10 | 647 | 70 | 2.756 | 84 | 3.307 | 6.500 | 165.1 | 1.965:1 | 7,257 |
4 | A10 stroker | 693 | 90 | 3.543 | 1.834:1 | 6,774 |
5 | A7 short stroke | 496 | 64.5 | 2.539 | 6.000 | 152.4 | 2.363:1 | 9,453 |
6 | A10 short rod | 647 | 84 | 3.307 | 1.814:1 | 7,257 |
“4K P-speed”: RPM at 4,000 feet per minute piston speed
ID:
1. A7 500cc pre-unit construction 1946-50 *-ZA7 11192
2. A7 500cc pre-unit construction 1951-* ZA7 11193-*
3. A10 650cc pre-unit construction
4. A10 stroked with billet crankshaft
5. Roland Pike 1953 special racer with A10 barrel, custom crankshaft; click for details: 
6. A10 with A7 rod, modified barrel |
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