311 Stock Engine Tech Section

Here is some general tech information on both the R16 and the U20 motors.
Item Desription SP(L)311-(R) SR(L)311-(U)
Model R16 U20
Displacement 1,595 1,982
Compression ratio 9.0 9.5
Max Power B.H.P./r.p.m.(SAE) 96/6000 SOLEX-150/6000 SU-135/6000
Intake valve clearance(hot) 0.0169 (in) 0.0079 (in)
Exhaust valve clearance(hot) 0.0169 (in) 0.0118(in)
Ignition timing BTDC/rpm 16/600 Solex-20/700 SU-16/700
Spark plugs NGK B-6E NGK B-6E
Spark plug gap 0.027~0.31 in. 0.027~0.31 in.
Point Gap 0.018~0.022 in. 0.018~0.022 in.
Firing order 1-3-4-2 1-3-4-2
Oil pan capacity US Gallon 1.083 Gl or 4-1/3 Qts Solex-1.875 Gl or 7.5 Qts SU-4-1/3 Qts
Minimum head thickness 3.246" 4.528-4.530"


Torque Specifications
Item Description SP(L)311-(R) SR(L)311-(U)
Cylinder head bolts 1st(ft-lbs) 17 43.4
Cylinder head bolts 2nd(ft-lbs) 34 62.1
Cylinder head bolts final(ft-lbs) 45~50 65.1
Connecting rod big end nuts 35~45 65.1
Flywheel bolts 35~44 57.8
Main bearing cap bolts 71~81 65.1
Camshaft bearing cap nuts M-8 N/A 13
Camshaft bearing cap nuts M-6 N/A 5.1
Cam shaft gear nut 33~36 13
Oil filter nuts 15.2~19.5 15.2~19.5
Oil pan 3.6 3.6
Oil pump 11~15 5.8~7.2
Crank pulley bolt 145 144.6
Jackshaft Sprocket screw N/A 32.5~36.2
Rocker cover 4.3~5.1 4.3~5.1




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