BMW motorcycle engines specs for the /5 and later models

Specifications for BMW motorcycle engines

by Duane Ausherman, but I don’t recall where I got them

 

Type            Air-cooled horizontally-opposed transverse twin, with pushrod
                  operated overhead valves.

Dimensions             Bore             Stroke           Capacity - Actual
  R45                  70.0mm (2.76")   61.5mm (2.42")   473.1cc (28.86 cu in)
  R50                  67.0mm (2.64")   70.6mm (2.78")   497.6cc (30.35 cu in)
  R60                  73.5mm (2.89")   70.6mm (2.78")   598.8cc (36.53 cu in)
  R65, R65LS           82.0mm (3.23")   61.5mm (2.42")   649.2cc (39.60 cu in)
  R75                  82.0mm (3.23")   70.6mm (2.78")   745.3cc (45.46 cu in)
  All 800cc models     84.8mm (3.34")   70.6mm (2.78")   797.1cc (48.62 cu in)
  R90/6, R90S          90.0mm (3.54")   70.6mm (2.78")   897.8cc (54.77 cu in)
  All 1000cc models    94.0mm (3.70")   70.6mm (2.78")   979.4cc (59.74 cu in)

Compression ratio (standard values quoted, some machines may have been fitted
with compression plates to reduce compression ratio from standard)
  R45                       9.2 : 1
  R50                       8.6 : 1
  R60                       9.2 : 1
  R65, R65LS                9.2 : 1
  R75                       9.0 : 1
  R80/7-40 kw version       9.2 : 1
  R80/7-37 kw version,
    all other 800cc models  8.2 : 1
  R90/6                     9.0 : 1
  R90S                      9.5 : 1
  R100/7                    9.0 : 1
  R100 (UK)                 8.2 : 1
  All other 1000cc models*  9.5 : 1
*All US machines from 1980 models onwards, compression ratio was reduced
to 8.2 : 1.

Recommended engine speeds - rpm:        Idle       Max.          Max.
                                                   permissible   permissible
                                                   continuous
  R45 R65 R65LS                         800-1100   7300          7650
  R50 R60/5 R60/6 R75/5 R75/6 R90/6     600-800    6500          7000
  R60/7                                 800-1100   6500          7200
  R75/7                                 800-1100   6500          7400
  All 800cc models                      800-1100   7200          7400
  R90S                                  600-800    7000          7300
  R100/7                                800-1100   6800          7400
  All other 1000cc models - UK -
    all R100T R100S 1977,78 - US -
    all except below                    800-1100   7000          7400
  All other 1000cc models - UK -
    all except those above - US - 
    R100RS 1977                         800-1100   7200          7400

Claimed engine output - DIN:         Max. power       Max. torque
                                     (kw/hp@rpm)      (Nm/lbf ft@rpm)
  R45                                26/35@7250       37.4/27.6@5500
  R50                                24/32@6400       38.3/28.3@5000
  R60                                29/40@6400       48.1/35.5@5000
  R65 1978-80 models*                33/45@7250       50.0/36.9@5500
  R65 1981 on models, R65LS*         37/50@7250       52.3/38.6@6500
  R75                                37/50@6200       58.8/43.4@5000
  R80/7 - high comp. version         40/55@7000       62.5/46.1@5500
  R80/7 - low comp. version          37/50@7250       56.6/41.8@5500
  R80G/S R80ST*                      37/50@6500       56.7/41.9@5000
  R80RT 1983, 84 models*             37/50@6500       59.0/43.5@3500
  R80, R80RT 85 on models*           37/50@6500       58.0/42.8@4000
  R90/6                              44/60@6500       73.0/53.9@5500
  R90S                               49/67@7000       76.0/56.1@5500
  R100/7                             44/60@6500       73.5/54.2@4000
  R100T - US*                        44/60@6500       74.6/55.1@5500
  R100T - UK, R100S - UK '77,
  '78 R100S - US, R100RS - US
  '78, '79, R100RT - US*             48/65@6600       75.0/55.4@5500
  R100 - UK                          49/67@7000       72.0/53.1@5500
  R100S - UK '79, '80, R100RS 
  - UK '77 - '80, R100RT - UK 
  '79, '80 R100RS - US '77*          51/70@7250       76.0/56.1@5500
  R100CS R100RS R100RT - UK
  models '81 on*                     51/70@7000       76.0/56.1@6000
*All models 1980 on - information applies only to UK models, not available
for US models.

Direction of engine rotation       clockwise, looking from front of machine

Compression pressure      R80G/S R80ST R80RT         All other models
                          R80 '85 on
  Good                    over 9.0bar (131psi)       over 10.0bar (145psi)
  Normal                  7.5-9.0bar (109-131psi)    8.5-10.0bar (123-145psi)
  Poor                    below 7.5bar (109psi)      below 8.5bar (123psi)

Valve clearances - engine cold           Normal           First 1000km (600m)
                                    Inlet      Exhaust    Inlet      Exhaust
  /5,/6                             0.15mm     0.20mm     N/Av       N/Av
                                    (.006")    (.008")
  /7,R80G/S,R80ST,R80RT '83-84      0.10mm     0.15mm     0.15mm     0.20mm
                                    (.004")    (.006")    (.006")    (.008")
  R45,R65,R65LS,R80,R80RT '85 on    0.10mm     0.20mm     0.15mm     0.25mm
                                    (.004")    (.008")    (.006")    (.010")

Valve timing - with 2.0mm (.08") valve clearance, tolerance of +-2.5 degrees.
                        R50/5 R60/5         R60/6 '76      R60/7 '78
                        R60/6 up to 1975    R60/7 '77
  Inlet opens           40 deg ATDC         TDC            6 deg BTDC
  Inlet closes          40 deg ABDC         40 deg ABDC    34 deg ABDC
  Exhaust opens         40 deg BBDC         40 deg BBDC    46 deg BBDC
  Exhaust closes        40 deg BTDC         TDC            6 deg BTDC

                        All R75 & R90,      R80/7 R100/7   All other models
                        R100/7 R100S        R100S 
                        R100RS '77          R100RS '78
  Inlet opens           10 deg BTDC         16 deg BTDC    16 deg BTDC
  Inlet closes          50 deg ABDC         44 deg ABDC    44 deg ABDC
  Exhaust opens         50 deg BBDC         56 deg BBDC    56 deg BBDC
  Exhaust closes        10 deg BTDC         4 deg BTDC     4 deg ATDC

Valves
  Head diameter:                       Inlet               Exhaust
    R45 R50                            34mm (1.34")        32mm (1.26")
    R60 R65 up to '80                  38mm (1.50")        34mm (1.34")
    R65 '81 on, R65LS                  40mm (1.58")        36mm (1.42")
    R75, all 800cc models              42mm (1.65")        38mm (1.50")
    R90/6 R90S R100/7                  42mm (1.65")        40mm (1.58")
    All other 1000cc models            44mm (1.73")        40mm (1.58")
  Head rim minimum thickness:
    /5 /6 /7                           1.0mm (0.0394")     1.0mm (0.0394")
    R80G/S R80ST R80RT '83-'84         0.8mm (0.0315")     0.8mm (0.0315")
    R45 R65 R65LS                      1.0-1.5mm           1.0-1.2mm
                                       (0.0394-0.0591")    (0.0394-0.0472")
  Head maximum runout:
    /5 /6 /7                           0.025mm (0.0010")   0.025mm (0.0010")
    R80G/S R80ST R80RT '83-84          0.020mm (0.0008")   0.020mm (0.0008")
  Overall length:
    R50/5                              102.6-103.0mm       102.1-102.5mm
                                       (4.0394-4.0551")    (4.0197-4.0354")
    R45 R65 R65LS                      98.8-100.2mm        99.1-99.5mm
                                       (3.8898-3.9449")    (3.9016-3.9173")
    R60/5 R60/6                        98.2-98.5mm         97.2-97.5mm
                                       (3.8661-3.8780")    (3.8268-3.8386")
    R60/7                              99.2-99.5mm         98.2-98.5mm
                                       (3.9055-3.9173")    (3.8661-3.8780")
    All other models                   98.4-98.8mm         98.4-98.8mm
                                       (3.8740-3.8898")    (3.8740-3.8898")

Valve Guides
  Length overall:
    /5 /6 except R90S                    54mm (2.1260")
    R90S, /7                             48mm (1.8898")
    R45 R65 R65LS                        45mm (1.7717")
    R80G/S R80ST R80RT '83-'84           44mm (1.7323")
  Outside diameter:
    /5 /6 /7 R80G/S R80ST R80RT '83-84   14.050-14.061mm (0.5532-0.5536")
    R45 R65 R65LS                        14mm (0.5512")
  Inside diameter:
    /5 /6 /7                             8mm (0.3150")
    R45 R65 R65LS                        7mm (0.2756")
    R80G/S R80ST R80RT '83-84            8.000-8.015mm (0.3150-0.3156")
  Bore in cylinder head:
    /5 /6 /7 R45 R65 R65LS               14mm (0.5512")
    R80G/S R80ST R80RT '83-84            14.000-14.018mm (0.5512-0.5519")
  Interference fit in cylinder head:
    /5 /6 /7                             0.032-0.061mm (0.0013-0.0024")
    All other models                     N/Av
  Oversizes available                    0.1 & 0.2mm (0.004 & 0.008")
  Valve stem/guide standard clearance:   Inlet                Exhaust
    R50/5                                0.040-0.070mm        0.050-0.080mm
                                         (0.0016-0.0028")     (0.0020-0.0032")
    R45 R65 R65LS                        0.025-0.055mm        0.040-0.070mm
                                         (0.0010-0.0022")     (0.0016-0.0028")
    R60                                  0.050-0.080mm        0.065-0.095mm
                                         (0.0020-0.0032")     (0.0026-0.0037")
    All other models                     0.050-0.080mm        0.050-0.080mm
                                         (0.0020-0.0032")     (0.0020-0.0032")
  Inlet and exhaust valve stem/guide max. permissible clearance - measured
  at top of guide:
    R45 R65 R65LS                        0.10mm (0.0039")
    All other models                     0.15mm (0.0059")

Valve seats
  Outside diameter:                      Inlet                Exhaust
    R50/5                                36.175-36.200mm      36.140-36.150mm
                                         (1.4242-1.4252")     (1.4228-1.4232")
    R45                                  36.2mm (1.4252")     36.2mm (1.4252")
    R60                                  39.175-39.200mm      39.175-39.200mm
                                         (1.5423-1.5433")     (1.5423-1.5433")
    R65 R65LS                            39.2mm (1.5433")     39.2mm (1.5433")
    R75/5                                43.175-43.200mm      43.140-43.150mm
                                         (1.6998-1.7008")     (1.6984-1.6988")
    R75/6 R90/6 R90S                     43.175-43.200mm      43.175-43.200mm
                                         (1.6998-1.7008")     (1.6998-1.7008")
    R75/7 R80/7 R100/7                   43.175-43.200m       43.134-43.200mm
                                         (1.6998-1.7008")     (1.6982-1.7008")
    R80G/S R80ST R80RT '83-84            43.175-43.200m       43.134-43.150mm
                                         (1.6998-1.7008")     (1.6982-1.6988")
    All other 1000cc models              45.175-45.200mm      45.175-45.200mm
                                         (1.7785-1.7795")     (1.7785-1.7795")
  Bore in cylinder head - inlet and exhaust:
    R50/5                                36.00-36.025mm (1.4173-1.4183")
    R45                                  36mm (1.4173")
    R60                                  39.00-39.025mm (1.5354-1.5364")
    R65, R65LS                           39mm (1.5354")
    All 745cc 800cc 900cc, R100/7        43.000-43.025mm (1.6929-1.6939")
    All other 1000cc models              45.000-45.025mm (1.7717-1.7727")
  Interference fit in cylinder head:     Inlet                Exhaust
    R50/5 R75/5                          0.150-0.200mm        0.115-0.150mm
                                         (0.0059-0.0079")     (0.0045-0.0059")
    R45 R65 R65LS                        N/Av                 N/Av
    R75/7 R80/7 R100/7 R80G/S R80ST
    R80RT '83-'84                        0.150-0.200mm        0.109-0.150mm
                                         (0.0059-0.0079")     (0.0043-0.0059")
    All other models                     0.150-0.200mm        0.150-0.200mm
                                         (0.0059-0.0079")     (0.0059-0.0079")
  Seat angle:
    Main seating face                    45 deg
    At combustion chamber                15 deg
    At inlet/exhaust port                75 deg
  Seat width:
    Inlet                                1.5mm (0.0591")
    Exhaust                              2.0mm (0.0787")
    Seat oversizes available             0.2 0.4mm (0.0079 0.0168")

Valve springs
  Wire thickness                         4.25mm (0.1673")
  Spring free length - approx:
    Blue or green code                   43.5mm (1.7126")
    Brown code                           46.0mm (1.811")
  Spring force at test length:
    At 37.6mm (1.4803")                  27.84-30.16 kp (61.30-66.5 lb)
    At 28.5mm (1.1221")                  70.00-72.80 kp (154.30-160.5 lb)

Rocker gear
  Arm ID -/5                             18.032-18.059mm (0.7099-0.7110")
  Bush OD -/5                            18.012-18.030mm (0.7091-0.7098")
  Arm/bush clearance -/5                 0.002-0.047mm (0.00008-0.00185")
  Bush ID /5                             14.532-14.559mm (0.5721-0.5732")
  Shaft OD /5                            14.512-14.530mm (0.5713-0.5720")
  Bush/shaft clearance /5                0.002-0.047mm (0.00008-0.00185")
  Arm axial float:
    R80 R80RT 1985                       0.03-0.07mm (0.0012-0.0028")
    All other models                     Nil, but arm must be free to move

Camshaft drive chain
  Type:
    /5 /6 /7 up to 1978                  Duplex roller chain
    All other models                     Single row chain
  Size                                   3/8 x 7/32"
  Number of links                        50

Camshaft
  Front (alternator end) bearing bore    40.000-40.039mm (1.5748-1.5763")
  Front flange bearing OD                39.984-40.000mm (1.5742-1.5748")
  Front flange bearing ID                25.000-25.013mm (0.9843-0.9848")
  Camshaft front bearing journal OD      24.967-24.980mm (0.9830-0.9835")
  Camshaft radial clearance - at 
    front bearing                        0.020-0.046mm (0.0008-0.0018")
  Rear (flywheel end) bearing bore       24.000-24.021mm (0.9449-0.9457")
  Camshaft rear bearing journal OD       23.967-23.980mm (0.9436-0.9441")
  Camshart radial clearance - at
    rear bearing                         0.020-0.054mm (0.0008-0.0021")
  Camshaft end float                     0.080-0.120mm (0.0032-0.0047")
  Base circle                            28mm (1.1024")
  Cam lift:
    R50/5 R60                            6.198mm (0.2440")
    All other models                     6.756mm (0.2660")
  Maximum permissible runout of ATU
    shaft - /5 /6 /7 up to '78           0.02mm (0.0008")

Cam followers and pushrods
  OD                                     21.955-21.975mm (0.8644-0.8652")
  Crankcase ID                           21.985-22.006mm (0.8656-0.8664")
  Follower/crankcase clearance:
    Standard                             0.010-0.051mm (0.0004-0.0020")
    Service limit                        0.075mm (0.0030")
  Pushrod length:
    R45 R65 R65LS /5 /6 up to '75        N/Av
    All other models                     274.7-275.3mm (10.8149-10.8386")

Crankshaft and main bearings
  Journal dimensions                     Basically the same, but tolerances vary
                                         according to model and year.
  Main bearing bushes                    Selective fit depending on journal
                                         dimensions and radial clearances.
  Main bearing journal/bush clearance:
    R45 (UK), R65 (UK), R65LS (UK),
    all /5 /6 /7                         0.035-0.065mm (0.0014-0.0025")
    /7 '81 on, R80G/S, R80ST, R65 (US),
    R65LS (US) - red size bush           0.017-0.066mm (0.0007-0.0026")
    /7 '81 on, R80G/S, R80ST, R65 (US),
    R65LS (US) - blue size bush          0.019-0.067mm (0.0008-0.0026")
  Crankshaft regrind stages:
    1st                                  0.25mm (0.0100")
    2nd                                  0.50mm (0.0200")
    3rd                                  0.75mm (0.0300")
  Max. runout - at front main bearing
    journal                              0.02mm (0.0008")
  Max. lateral runout at flywheel        0.10mm (0.0008")
  Crankshaft standard endfloat           0.08-0.15mm (0.0032-0.0059")
  Thrust washer thickness:
    Standard - red                       2.483-2.530mm (0.0978-0.0996")
    Standard - blue                      2.530-2.578mm (0.0996-0.1015")
    Standard - green                     2.578-2.626mm (0.1015-0.1034")
    Standard - yellow                    2.626-2.673mm (0.1034-0.1052")
    Wear limit - all                     minus 0.20mm (0.0079")

Connecting rods and bearings
  Crankpin standard OD                   47.975-47.991mm (1.8888-1.8894")
  Crankpin regrind stages:
    1st                                  0.25mm (0.0100") 
    2nd                                  0.50mm (0.0200")
    3rd                                  0.75mm (0.0300")
  Connecting rod big-end ID - less bearing shells:
    /5, /6, /7 1977                      52.000-52.010mm (2.0472-2.0476")
    All other models                     52.000-52.015mm (2.0472-2.0478")
  Con. rod radial clearance              0.023-0.069mm (0.0009-0.0027")
  Con. rod big-end width                 21.883-21.935mm (0.8615-0.8636")
  Crankpin width                         22.065-22.149mm (0.8657-0.8720")
  Con. rod axial clearance (endfloat):
    Standard                             0.130-0.266mm (0.0051-0.105")
    Max. permissible                     0.320mm (0.0126")
  Max. weight difference between con. rods:
    /5, /6                               6 grams (0.2116 oz)
    /7, R45, R65, R65LS                  3 grams (0.1058 oz)
    R80G/S, R80ST                        2 grams (0.0705 oz)
  Con. rod small-end ID - less bush      24.000-24.021mm (0.9449-0.9457")
  Small-end bush OD                      24.060-24.100mm (0.9472-0.9488")
  Small-end bush ID:
    Standard                             22.015-22.020mm (0.8667-0.8669")
    Max. permissible                     22.040mm (0.8677")
  Gudgeon pin/small-end bush clearance:
    /5,/6,/7 up to '80 - white coded pin 0.015-0.023mm (0.0006-0.0009")
    /5,/6,/7 up to '80 - black coded pin 0.018-0.026mm (0.0007-0.0010")
    /7 '81 on,R80G/S,R80ST               0.015-0.024mm (0.0006-0.0009")
    R45,R65,R65LS                        0.015-0.025mm (0.0006-0.0009")
  Gudgeon pin OD:
    /5,/6,/7 up to '80 - white coded pin 21.997-22.000mm (0.8660-0.8661")
    /5,/6,/7 up to '80 - black coded pin 21.994-21.997mm (0.8659-0.8660")
    /7 '81 on,R80G/S,R80ST               21.996-22.000mm (0.8659-0.8661")
    R45,R65,R65LS                        21.995-22.000mm (0.8659-0.8661")
  Gudgeon pin bore ID - in piston:
    /5,/6,/7 up to '80 - white code
    (W stamped in piston crown)          22.000-22.003mm (0.8661-0.8662")
    /5,/6,/7 up to '80 - black code
    (S stamped in piston crown)          21.997-22.000mm (0.8660-0.8661")
    /7 '81 on,R80G/S,R80ST               22.000-22.004mm (0.8661-0.8663")
    R45                                  22.002-22.007mm (0.8662-0.8664")
    R65,R65LS                            22.005-22.010mm (0.8663-0.8665")
  Gudgeon pin/piston clearance:
    /5,/6,/7 up to '80                   0.000-0.006mm (0.0000-0.0002")
    /7 '81 on,R80G/S,R80ST               0.000-0.008mm (0.0000-0.0003")
    R45                                  0.002-0.012mm (0.0001-0.0005")
    R65,R65LS                            0.005-0.015mm (0.0002-0.0006")

Cylinders
  Type:
    All models up to 1980      Cast iron sleeve joined to aluminium alloy
                               finned jacket by 'Al-Fin' process
    R45,R65,R65LS '81 on       Aluminium alloy barrel with 'Nikasil' plated bore
    1000cc and 800cc, '81 on   Aluminium alloy barrel with 'Galnikal' plated
                               bore
    Cylinder standard bore ID - at specified bore size code:
                               A                B                C
    R50/5                      67.000mm         67.010mm         67.020mm
                               (2.7368")        (2.6382")        (2.6386")
    R45                        69.995-70.005mm  70.005-70.015mm  70.015-70.025mm
                               (2.7557-2.7561") (2.7561-2.7565") (2.7565-2.7569")
    R60/5,R60/6                73.500mm         73.510mm         73.520mm
                               (2.8937")        (2.8941")        (2.8945")
    R60/7                      73.500-73.510mm  73.510-73.520mm  73.520-73.530mm
                               (2.8937-2.8941") (2.8941-2.8945") (2.8945-2.8949")
    R65,R65LS                  81.995-82.005mm  82.005-82.015mm  82.015-82.025mm
                               (3.2281-3.2285") (3.2285-3.2289") (3.2289-3.2293")
    R75/5,R75/6                82.000mm         82.010mm         82.020mm
                               (3.2283")        (3.2287")        (3.2291")
    R75/7                      82.005-82.015mm  82.015-82.025mm  82.025-82.035mm
                               (3.2285-3.2289") (3.2289-3.2293") (3.2293-3.2297")
    All 800cc models           84.795-84.805mm  84.805-84.815mm  84.815-84.825mm
                               (3.3384-3.3388") (3.3388-3.3392") (3.3392-3.3396")
    R90/6,R90S                 90.000mm         90.010mm         90.020mm
                               (3.5433")        (3.5437")        (3.5441")
    All 1000cc models          94.005-94.015mm  94.015-94.025mm  94.025-94.035mm
                               (3.7010-3.7014") (3.7014-3.7018") (3.7018-3.7022")
  Rebore sizes:
    /5,/6,R60/7,R75/7 - 1st      0.50mm (0.020")
    /5,/6,R60/7,R75/7 - 2nd      1.00mm (0.040")
    R45&R65 to '80,R80/7 - 1st   0.25mm (0.010")
    R45&R65 to '80,R80/7 - 2nd   0.50mm (0.020")
    All 1000cc models to '80     0.25mm (0.010")
    All models '81 on            rebores not possible, pistons and cylinders 
                                 must be renewed when excessively worn
  Maximum ovality:
    R45,R65,R65LS                                 0.005mm (0.0002")
    R80G/S,R80ST - 20mm (0.8") from top of bore   0.005mm (0.0002")
    R80G/S,R80ST - 115mm (4.5") from top of bore  0.010mm (0.0004")
    All other models                              0.010mm (0.0004")
  Maximum taper:
    /5,/6                                         0.010mm (0.0004")
    All other models                              0.020mm (0.0008")

Pistons
  Standard OD - at specified size code:
                             A                B                C
    R50/5                    66.960mm         66.970mm         66.980mm
                             (2.6362")        (2.6366")        (2.6370")
    R45                      69.955-69.965mm  69.965-69.975mm  69.975-69.985mm
                             (2.7541-2.7545") (2.7545-2.7549") (2.7549-2.7553")
    R60/5,R60/6              73.460mm         73.470mm         73.480mm
                             (2.8921")        (2.8925")        (2.8929")
    R60/7                    73.470mm         73.480mm         73.490mm
                             (2.8925")        (2.8929")        (2.8933")
    R65,R65LS                81.955-81.965mm  81.965-81.975mm  81.975-81.985mm
                             (3.2266-3.2270") (3.2270-3.2274") (3.2274-3.2278")
    R75/5,R75/6              81.960mm         81.970mm         81.980mm
                             (3.2268")        (3.2272")        (3.2276")
    R75/7                    81.965mm         81.975mm         81.985mm
                             (3.2270")        (3.2274")        (3.2278")
    All 800cc models         84.765mm         84.775mm         84.785mm
                             (3.3372")        (3.3376")        (3.3380")
    R90/6,R90S               89.960mm         89.970mm         89.980mm
                             (3.5417")        (3.5421")        (3.5425")
    All 1000cc models        93.960mm         93.970mm         93.980mm
                             (3.6992")        (3.6996")        (3.7000")
  Standard piston/cylinder clearance:
    /5,/6                        0.035-0.045mm (0.0014-0.0018")
    R60/7                        0.020-0.040mm (0.0008-0.0016")
    R75/7                        0.019-0.041mm (0.0007-0.0016")
    R80/7                        0.023-0.047mm (0.0009-0.0029")
    R45 & R65 up to '80          0.030-0.050mm (0.0012-0.0020")
    All 1000cc models up to '80  0.028-0.052mm (0.0011-0.0021")
    All models '81 on            0.030-0.040mm (0.0012-0.0016")
  Maximum permissible piston/cylinder clearance:
    /5,/6                        0.120mm (0.0047")
    All other models             0.080mm (0.0032")
  Piston weight group            + or - stamped in piston crown - both
                                 pistons must be of the same weight group,
                                 i.e. carry the same marking.

Piston rings
  Top:
    Type                       Plain, rectangular section
    Thickness:
      /5,/6                    1.790-1.810mm (0.705-0.0713")
      R45                      1.478-1.490mm (0.582-0.0587")
      All other models         1.728-1.740mm (0.0680-0.0685")
    End gap - installed:
      R50,R60                  0.25-0.40mm (0.0098-0.0158")
      R45                      0.25-0.45mm (0.0098-0.0177")
      R75/5,R75/6,R90/6,R90S   0.30-0.45mm (0.0118-0.0177")
      /7 '81 on                0.40-0.65mm (0.0158-0.0256")
      All other models         0.30-0.50mm (0.0118-0.0197")
    Side clearance:
      /5,/6                    0.060-0.070mm (0.0024-0.0028")
      /7                       0.060-0.090mm (0.0024-0.0035")
      All other models         0.050-0.082mm (0.0020-0.0032")
  Second:
    Type                       Plain, with stepped or tapered face
    Thickness
      /5,/6                    2.030-2.050mm (0.0799-0.0807")
      /7, R45 up to '80        2.010-2.022mm (0.0791-0.0796")
      All other models         1.978-1.990mm (0.0779-0.0784")
    End gap - installed:
      R50,R60                  0.25-0.40mm (0.0098-0.0158")
      R45                      0.25-0.45mm (0.0098-0.0177")
      R80G/S,R80ST             0.30-0.50mm (0.0118-0.0197")
      /7 '81 on                0.40-0.65mm (0.0158-0.0256")
      All other models         0.30-0.45mm (0.0118-0.0177")
    Side clearance:
      /5,/6                    0.050-0.060mm (0.0020-0.0024")
      All other models         0.040-0.072mm (0.0016-0.0028")
  Oil scraper:
    Type                       One piece
    Thickness:
      /5,/6                    4.010-4.030mm (0.1579-0.1587")
      /7                       4.010-4.022mm (0.1579-0.1584")
      R80G/S,R80ST,R45 '81 on  3.478-3.490mm (0.1369-0.1374")
      R45 up to '80            3.510-3.522mm (0.1382-0.1387")
      R65,R65LS                3.978-3.990mm (0.1566-0.1571")
    End gap - installed:
      R50/5,R60/5              0.20-0.35mm (0.0079-0.0138")
      R60/6,R60/7              0.25-0.35mm (0.0098-0.0138")
      R45                      0.25-0.45mm (0.0098-0.0177")
      All other models         0.25-0.40mm (0.0098-0.0158")
    Side clearance:
      /5,/6                    0.030-0.040mm (0.0012-0.0016")
      R60/7                    0.020-0.050mm (0.0008-0.0020")
      All other models         0.030-0.062mm (0.0012-0.0024")

Torque wrench settings
  Component:                                              Nm       lb/ft
    Rocker cover cap nut - R8,R80RT '85 on                20       15
    Spark plugs                                           20-30    15-22
    Valve adjuster locknuts                               18-23    13.5-17
    Cylinder head retaining nuts - all models up to '80:
      1st stage                                           15       11
      2nd stage                                           35       26
      3rd stage                                           40       29.5
      Standard setting                                    38-42    28-31
    Cylinder head retaining nuts - all models '81 on:
      1st stage                                           15       11
      2nd stage                                           25       18.5
      3rd stage                                           35       26
      Standard setting                                    35-39    26-29
    Exhaust pipe finned nuts:
      R80,R80RT '85 on                                    160      118
      R45 & R65 '79-'80,/7 up to '80                      140-180  103-133
      All other models                                    200-220  148-162
    Connecting rod bolts                                  48-52    35.5-38
    Flywheel mounting bolts:
      /5                                                  58-62    43-46
      R60/6 & R75/6 up to 9/74 - 10mm bolts               60-65    44-48
      R90/6 & R90S up to 9/74 - 10mm bolts                70-75    52-55
      /6 '75 on and all other models - 11mm bolts         100-105  74-77.5
    Oil pump pickup mounting bolts                        9        6.5
    Camshaft flange bearing - all models '79 on           15-18    11-13.5
    Sump mounting bolts                                   9-12     6.5-9
    Alternator rotor retaining bolt                       23-27    17-20
    Starter motor mounting bolts                          47.5     35
    ATU retaining nut:
      /5,/6                                               6-7      4.5-5
      /7 up to '78                                        5-6      4-4.5
      All other models                                    N/App    N/App
    Oil filter inner cover retaining bolt - /5,/6 only    41       30
    Engine oil drain plug:
      Models up to '80                                    N/Av     N/Av
      All models '81 on                                   41       30
    Oil filter cover mounting bolts                       10       7.5
    Engine mounting nuts:
      R80,R80RT '85 on                                    54.2     40
      All other models                                    70-77    52-57

These specifications were provided by BMW.