S&S Cycle Bore Big Twin Stroker Kit 1936–1999 3 7/16 - 3 1/2 - Manual (Page 16)

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NOTEs:
•
Material removed from pistons for clearancing purposes will not adversely affect flywheel balance.
• Some S&S® kits utilize flywheels with diameters smaller than stock (stock big twin flywheels are 81⁄2"). This is done to maximize piston skirt length. Our
experience has shown that when small diameter flywheels are used it is desirable but not absolutely necessary to build up flywheel scraper. If flywheel
scraper is not built up, oil thrown off flywheels may cause excessive oil burning in the rear cylinder.
4. Breather Timing (All)
To maximize efficiency when scavenging oil from flywheel cavity in Big Twin engines, it is necessary to check and usually modify crankcase
breather timing.
NOTEs:
•
Breather timing can be checked after other crankcase clearancing is done or during initial disassembly.
• Early crankcases had an elliptical hole for the breather. Later models were changed to a square breather opening.
•
Objective of this step is to modify cases so that hole in cases is located in same position as hole in breather gear with opening and closing sides of hole
in case in correct location for proper breather timing.
• S&S PN 53-0020, degree wheel kit, was designed to aid in checking breather timing. Procedures below assume an S&S degree wheel is used.
• S&S recommends grinding hole to maximum timing specifications. If there is any doubt and timing falls within specs, leave breather opening alone.
see Figure 7 for breather timing specifications.
R O
TATION
Opening Side
Closing Side
1.165 .690
Figure 7