SER FAQ: LMFAQ: Typical mechanical specifications

S.E.R. FAQ

NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Typical mechanical specifications
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Small Engine Specifications

Typical mechanical specifications

The following are some of the key dimensions and other specifications for several common Tecumseh engines. Where two numbers are listed, they are the upper and lower service (wear) limits as appropriate. One of these will be close to the expected dimension on a new engine; the other represents the point at which you are supposed to replace the part due to wear. All values are in inches unless otherwise noted.

        Specification        LAV/H30   LAV/H40   LAV/H50    V/H70    VM/HM100
-------------------------------------------------------------------------------

Horsepower:                     3         4         5        7         10

Displacement (cubic inches):  7.75     10.5      11.5      15.0      20.2

Bore:                         2.3125    2.625     2.75      2.75      3.187

Stroke:                      1-27/32   1-15/16   1-15/16   2-17/32   2-17/32

Timing Dimension:              .060      .035      .035      .050      .070
(before TDC)

Point setting:                 .020      .020      .020      .020      .020

Spark plug gap:                .030      .030      .030      .030      .030

Valve Clearance:               .010      .010      .010      .010      .010

Valve seat angle (degrees):     46        46        46        46        46

Valve spring free length:     1.135     1.135     1.135     1.462     1.462

Valve seat width:              .035      .035      .035      .042      .042
                               .045      .045      .045      .052      .052

Crankshaft end play:           .005      .005      .005      .005      .005
                               .027      .027      .027      .027      .027

Crank pin journal diameter:    .8610     .9995     .9995    1.1865    1.1865
                               .8615    1.0000    1.0000    1.1870    1.1870

Connecting rod bearing diam:   .8620    1.0005    1.0005    1.1880    1.1880
(crank pin journal end)        .8625    1.0010    1.0010    1.1885    1.1885

Crankshaft diameter:           .8735     .9985     .9985     .9985    1.1870
(cover/blade/PTO)              .8740     .9990     .9990     .9990    1.1875

Main bearing diameter:         .8755    1.0005    1.0005    1.0005    1.1890
(cover/blade/PTO)              .8760    1.0010    1.0010    1.0010    1.1895

Crankshaft Diameter:           .8735     .9985     .9990     .9985     .9985
(flywheel/magneto)             .8740     .9990     .9995     .9990     .9990

Main bearing diameter:         .8755    1.0005    1.0005    1.0005    1.0005
(flywheel/magneto)             .8760    1.0010    1.0010    1.0010    1.0010

Camshaft bearing diameter:     .4975     .4975     .4975     .6230     .6230
                               .4980     .4980     .4980     .6235     .6235

Piston diameter:              2.3090    2.6260    2.7450    2.7450    3.1817
                              2.3095    2.6265    2.7455    2.7455    3.1842

Piston pin diameter:           .5629     .5629     .5629     .6248     .6248
                               .5631     .5631     .5631     .6250     .6250

Width of comp. ring grooves:   .0955     .0925     .0795     .0795     .0955
                               .0977     .0935     .0815     .0805     .0975

Width of oil ring grooves:     .125      .156      .1565     .188      .188
                               .127      .158      .1585     .190      .190

Ring end gap:                  .007      .007      .007      .007      .007
                               .020      .020      .020      .020      .020

Top piston land clearance:     .0105     .0165     .024      .023      .029
                               .0145     .0215     .027      .028      .034

Piston skirt clearance:        .0025     .0045     .0045     .0045     .028
                               .0040     .0060     .0060     .0060     .053

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