Tech Tip: BSA Torque Wrench Figures
Recently I uncovered some original BSA service bulletins that where originally from the BSA "western facility" in Duarte, California
Flipping through the binder of many pages I stumbled across some hard to find information - torque wrench settings and figures
Today I would like to dedicate this post to all the torque wrench figures in each service bulletin that I have
Although this page may not have every single torque figure for every model, however, the figures as described below are important and will be useful should you have any of the models below
As I find more BSA service bulletins with different models and year ranges, I will update this post accordingly
Click here for more Triumph and BSA service bulletins
Enjoy..
Abbreviations
| TPI | Threads per inch |
| Hex A/F | Hexagon across flats |
| SL | Self locking |
| BSC | British standard cycle |
| BSF | British standard form |
| UNF | Unified fine |
| WF | Whitworth form |
| LHT | Left hand thread |
| UNC | Unified coarse |
| UNS | Unified special |
1967 BSA 441 Victor
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Below are the recommend BSA torque wrench figures for BSA B44 Victor (441) models dated from 1967
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts | .3125" (5/16) BSC | 26 | .525" | 10 |
| Clutch center nut | .500" (1/2) BSC | 20 | .820" | 60/65 |
| Crankpin nuts | .875" (7/8) WF | 20 | 1.480" | 200 |
| Crankshaft pinion nut | .625" (5/8) BSF | 20 | .919" | 35/40 |
| Cylinder barrel nuts | .4375" (7/16) BSC | 20 | .600" | 30/33 |
| Cylinder head stud nuts | .3125" (5/16) BSC | 26 | .525" | 18/20 |
| Kickstart ratchet nut | .500" (1/2) BSC | 20 | .705" | 50/55 |
| Oil pump studs nuts | .250" (1/4) BSC | 26 | .445" | 5/7 |
| Rotor fixing nut | .625" (5/8) BSC | 20 | 1.010" | 60 |
| Valve cover nuts | .3125" (5/16) BSC | 26 | .525" | 10 |
| Valve cover nuts | .250" (1/4) BSC | 26 | .440" | 5/7 |
| Front fork cap nuts | 1.0625" WF | 20 | 1.300" | 50/55 |
| Front fork bottom yoke nuts | .375" (3/8) UNF | 24 | .562" | 23/25 |
1967 BSA B25 / C25
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Below are the recommend BSA torque wrench figures for BSA B25 & C25 Starfire (250) models dated from 1967
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts (SL) | .3125" (5/16) BSC | 26 | .525" | 10 |
| Clutch center nut | .500" (1/2) BSC | 20 | .820" | 60/65 |
| Con-rod end cap nuts (SL) | .3125" (5/16) BSC | 26 | .525" | 25/27 |
| Crankshaft pinion nut | .625" (5/8) BSF | 20 | .919" | 35/40 |
| Cylinder barrel nuts | .375" (3/8) UNF | 24 | .558" | 26/28 |
| Cylinder head stud nuts | .3125" (5/16) BSC | 26 | .525" | 18/20 |
| Fork leg cap nuts | 1.0625" WF | 20 | 1.300" | 50/55 |
| Fork leg pinch bolts | .3125" (5/16) BSC | 26 | .525" | 18/20 |
| Kickstart ratchet nut | .500" (1/2) BSC | 20 | .705" | 50/55 |
| Oil pump studs nuts (SL) | .250" (1/4) BSC | 26 | .445" | 5/7 |
| Rotor fixing nut | .625" (5/8) BSC | 20 | 1.010" | 60 |
| Valve cover nuts | .3125" (5/16) BSC | 26 | .525" | 10 |
| Valve cover nuts | .250" (1/4) BSC | 26 | .440" | 5/7 |
1967 BSA A50 & A65
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Below are the recommend BSA torque wrench figures for BSA A50 & A65 models dated from 1967
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts | 5/16 BSC | 26 | .525" | 10 |
| Clutch center nut | 9/16 BSC | 20 | .920" | 65/70 |
| Crankcase stud nuts | 5/16 BSC | 26 | .525" | 16/18 |
| Oil pump drive worm (LHT) | 9/16 BSC | 20 | .781" | 28/30 |
| Connecting rod bolts | 5/16 BSC | 26 | .485" | 22 |
| Cylinder barrel nuts | 5/16 BSC | 26 | .525" | 18/20 |
| Cylinder head bolts | 3/8 BSF | 20 | .594" | 28/30 |
| Cylinder head bolts | 3/8 BSF | 20 | .525" | 28/30 |
| Cylinder head nuts | 3/8 BSC | 26 | .600" | 31/33 |
| Flywheel bolts | 3/8 BSC | 26 | .525" | 45 |
| Kickstart ratchet nut | 9/16 BSC | 20 | .820" | 55/60 |
| Manifold stud nuts | 1/4 BSC | 26 | .375" | 6 |
| Oil pump studs nuts | 1/4 BSC | 26 | .440" | 8/10 |
| Rotor fixing nut | 5/8 BSC | 20 | 1.010" | 60 |
| Stator fixing nuts (SL) | 1/4 BSC | 26 | .440" | 8/10 |
| Zener diode nut | 1/4 UNF | 28 | .437" | 2/2.3 |
| Front fork cap nuts | 1 1/16 WF | 20 | 1.300" | 50/55 |
| Front fork bottom yoke bolts | 3/8 UNF | 24 | .562" | 23/25 |
1968-1970 BSA A50 & A65
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Below are the recommend BSA torque wrench figures for BSA A50 & A65 models dated from 1968-1970
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts | 5/16 BSC | 26 | .525" | 10 |
| Clutch center nut | 9/16 BSC | 20 | .920" | 65/70 |
| Crankcase stud nuts | 5/16 UNF | 24 | .500" | 16/18 |
| Oil pump drive worm (LHT) | 9/16 BSC | 20 | .781" | 28/30 |
| Connecting rod bolts | 5/16 BSC | 26 | .485" | 22 |
| Cylinder barrel nuts | 5/16 UNF | 24 | .500" | 18/20 |
| Cylinder head bolts | 3/8 BSF | 20 | .594" | 28/30 |
| Cylinder head bolts | 3/8 BSF | 20 | .525" | 28/30 |
| Cylinder head nuts | 3/8 BSC | 26 | .600" | 31/33 |
| Flywheel bolts | 3/8 BSC | 26 | .525" | 45 |
| Kickstart ratchet nut | 9/16 BSC | 20 | .820" | 55/60 |
| Manifold stud nuts | 1/4 BSC | 26 | .375" | 6 |
| Oil pump studs nuts | 1/4 UNF | 28 | .437" | 8/10 |
| Rotor mounting nut | 5/8 BSC | 20 | 1.010" | 60 |
| Stator mounting nuts (SL) | 5/16 UNF | 24 | .437" | 5/7 |
| Zener diode nut | 1/4 UNF | 28 | .437" | 2/2.3 |
| Front fork cap nuts | 1 1/16 UNF | 28 | 1.500" | 50/55 |
| Front fork bottom yoke bolts | 3/8 UNF | 24 | .562" | 23/25 |
1969-1970 BSA A75 Rocket III
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Below are the recommend BSA torque wrench figures for BSA A75 Rocket III models dated from 1969-1970
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Alternator rotor nut | .4375" UNF | 20 | .9375" | 50 |
| Clutch center nut | .5625" UNF | 18 | .875" | 60 |
| Connecting rod bolt nuts (SL) | .3125" UNF | 24 | .500" | 17 1/2 - 18 1/2 |
| Crankcase junction bolts | .3125" UNC | 18 | .500" | 12 |
| Crankcase junction stud nuts | .3125" UNF | 24 | .500" | 12 |
| Cylinder barrel nuts | .375" UNF | 24 | .5625" | 20-22 |
| Cylinder head bolts | .3125" UNF | 24 | .500" | 18 |
| Engine sprocket nut | .750" UNF | 20 | 1.125" | 58/63 |
| Gearbox output shaft nut | 1.25" UNF | 28 | 1.675" | 58 |
| Kickstart ratchet nut | .5625" UNF | 18 | .9375" | 40/45 |
| Main bearing cap stud nuts (SL) | .375" UNF | 24 | .5625" | 23/25 |
| Rocker box bolts | .250" UNC | 20 | .4375" | 6 |
| Rocker box stud nuts | .250" UNF | 28 | .4375" | 6 |
| Rotor mounting nut | 5/8 BSC | 20 | 1.010" | 60 |
| Shock absorber nut (SL) | .3125" UNF | 24 | .445" | 8 |
| Stator mounting nuts (SL) | .3125" UNF | 24 | .4375" | 8 |
| Zener diode nut | 1/4 UNF | 28 | .437" | 2/2.3 |
| Front fork top cap nuts | 1.0625" UNF | 28 | 1.500" | 75/80 |
| Front fork bottom yoke bolts | .375" UNF | 24 | .562" | 23/25 |
| Front fork top yoke pinch bolts | .375" UNF | 24 | .5625" | 23/25 |
| Front wheel spindle cap bolts | .3125" UNF | 24 | .500" | 23/25 |
1968-1970 BSA 441 Victor
Click the image above to enlarge this service bulletin - you can print, save and share...
Below are the recommend BSA torque wrench figures for BSA B44 Victor (441) models dated from 1968-1970
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts (SL) | .3125" (5/16) BSC | 26 | .525" | 10 |
| Clutch center nut | .500" (1/2) BSC | 20 | .820" | 60/65 |
| Crankpin nuts | .875" (7/8) WF | 20 | 1.480" | 200 |
| Crankshaft pinion nut | .625" (5/8) BSF | 20 | .919" | 35/40 |
| Cylinder barrel nuts | .4375" (7/16) UNF | 20 | .6875" | 30/33 |
| Cylinder head stud nuts | .3125" (5/16) BSC | 26 | .525" | 18/20 |
| Kickstart ratchet nut | .500" (1/2) BSC | 20 | .705" | 50/55 |
| Oil pump studs nuts | .250" (1/4) UNF | 28 | .437" | 5/7 |
| Rotor mounting nut | .625" (5/8) BSC | 20 | 1.010" | 60 |
| Rocker box nuts | .3125" (5/16) BSC | 26 | .525" | 10 |
| Rocker box nuts | .250" (1/4) BSC | 26 | .440" | 5/7 |
| Front fork cap nuts | 1.0625" WF | 20 | 1.300" | 50/55 |
| Front fork bottom yoke nuts | .375" (3/8) UNF | 24 | .562" | 23/25 |
| Stator mounting nuts | .250" (1/4) UNF | 28 | .437" | 5/7 |
1968-1970 BSA B25 / C25
Click the image above to enlarge this service bulletin - you can print, save and share...
Below are the recommend BSA torque wrench figures for BSA B25 & C25 Starfire (250) models dated from 1968-1970
| Application | Thread Diameter & Type | TPI | Hex A/F | Torque (lb ft) |
| Carb flange nuts (SL) | .3125" (5/16) BSC | 26 | .525" | 10 |
| Clutch center nut | .500" (1/2) BSC | 20 | .820" | 60/65 |
| Con-rod end cap nuts (SL) | .3125" (5/16) BSC | 26 | .525" | 25/27 |
| Crankshaft pinion nut | .625" (5/8) BSF | 20 | .919" | 35/40 |
| Cylinder barrel nuts | .375" (3/8) UNF | 24 | .558" | 26/28 |
| Cylinder head stud nuts | .3125" (5/16) BSC | 26 | .525" | 18/20 |
| Fork leg cap nuts | 1.0625" WF | 20 | 1.300" | 50/55 |
| Fork leg pinch bolts | .375" (3/8) UNF | 24 | .562" | 18/20 |
| Kickstart ratchet nut | .500" (1/2) BSC | 20 | .705" | 50/55 |
| Oil pump studs nuts (SL) | .250" (1/4) UNF | 28 | .437" | 5/7 |
| Rotor fixing nut | .625" (5/8) BSC | 20 | 1.010" | 60 |
| Rocker box nuts | .3125" (5/16) BSC | 26 | .525" | 10 |
| Rocker box nuts | .250" (1/4) BSC | 26 | .440" | 5/7 |
| Stator mounting nuts | .250" (1/4) UNF | 28 | .437" | 5/7 |
Toddy ‘Brien
1970 BSA A.65 Thunderbolt
Peter Thomas Gaby
Just a word thanks for passing on this information, I have a sizeable collection factory bulletin’s but none include the factory torque values.
Again my thanks & kindest regards,
Peter.
Peter-Thomas Gaby. Ottawa, Ontario, Canada.
Davo
Magic