STD Bore - 40RL71G 40HP

[PaulO]

Can anyone confirm the standard bore for this engine is 3.187"

 

[oldcatamount]

Re: STD Bore - 40RL71G 40HP

The standard bore size for a 1971 40hp is 3.19 (and the standard stroke is 2.82).

 

[PaulO]

Re: STD Bore - 40RL71G 40HP

oldcatamount

I can't see a bore size for 3.19" in the online parts. It only shows 3.187. .003" is suppose to be the out of round tolerence/max wear. I'm confused.

Do you have a part number for me?

 

[oldcatamount]

Re: STD Bore - 40RL71G 40HP

I don't have a part number. This is the dimension from a manual. Hopefully someone else will have a part number or the correct bore size. Don't bore the block on just my say so. Let's get some confirmation first.

 

[Faztbullet]

Re: STD Bore - 40RL71G 40HP

Below is some information you find helpful I hope.. and the 1968-1974 shared the same bore

TUNE-UP 33 hp 40 hp
Hp @ rpm 33 @ 4500 4 0 @ 4500
Bore?Inches 3 1/16 3 3/16= 3.187
Stroke?Inches 2.75 2.75
Number of Cylinders 2 2
Displacement?C.I. 40.5 43.9
Spark Plugs
Champion J4J J4J
Electrode Gap 0.030 0.030
Magneto
Point Gap 0.020 0.020
Fuel-Oil Ratio 50:1 50:1

SIZES & CLEARANCES
Piston Rings
End Gap 0.007-0.017 0.007-0.017
Side Qearonce 0.0045-0.007 0.0045-0.007
Piston Skirt wear 0.003-0.0045 0.003-0.0045
Crankshaft End Play 0.007-0.011 0.003-0.011
TIGHTENING TORQUES
(All Values In Inch-Pounds Unless Noted)
Connecting Rod 348-372 348-372
Crankcase Halves
Center Screws 162-168 162-168
Flange Screws 150-170 150-170
CyUnder Head 168-192 168-192
Inlet Manifold 24-36 24-36
Exhaust Manifold 60-84 60-84
Flywheel (Ft.-Lbs.) 100-105 100-105
Spark Plug 240-246 240-246

 

[PaulO]

Re: STD Bore - 40RL71G 40HP

Fatzbullet

I appreciate your efforts. Thankyou very much.

 

[PaulO]

Re: STD Bore - 40RL71G 40HP

Can anyone tell me book figures as to what the skirt diameter is for a piston to fit a 3.187" bore?

 

[PaulO]

Re: STD Bore - 40RL71G 40HP

As above