This site uses cookies. The cookies we use are essential for parts of the site to operate. You may delete and block all cookies from this site causing sections to not work.

 
Dealer Locator








Facebook

Youtube

PERFORMANCE MOTORCYCLE PARTS AND KITS FOR AMERICAN V-TWINS

S&S Cycle logo

How to Identify Flywheels

S&S® flywheels are manufactured in sets only. We do not sell individual right or left flywheels, nor do we recommend mixing flywheels. This is because the manufacturing techniques and/or tooling changes periodically. To prevent mixing flywheels, as well as to identify each set, the right and left flywheels are stamped with identical serial numbers (see picture below).


Flywheel serial number

 
 
Serial Number Identification Information
Serial Number ID, B01810-3SLX , deciphered as follows:

(B01810) Serial Number: From this number, S&S can determine when the flywheels were made and sold, to whom they were sold, and how the flywheels were originally balanced.

(3) Stroke Code: Determines the stroke of the flywheels. In this case the stroke is 4 3/4".

(SL) Year Code: The year of the engine the flywheels were machined to fit and that the flywheels were machined to accept an S&S design sprocket shaft.

(X) Diameter Code: Diameter of the flywheels. In this case the diameter is 8 1/4".


 S&S® Flywheel Identification Codes for 1936–Up Big Twins
Stroke Code Stroke Year Code Engine Year Sprocket Shaft Pinion Shaft Crankpin Type Diameter Code Flywheel Diameter
1 4 3⁄8" E 1936–'54 Stock Stock 1941–'81 None

8 1⁄2" (Stock)

  4 1⁄2" L 1955–'71 Stock Stock 1941–'81 A 8 3⁄8"
3 4 3⁄4"   AL

1972–
Early '81

Stock Stock 1941–'81 X 8 1⁄4"
4 5" SE 1955–Early '81 S&S Stock 1941–'81    
 

4 1⁄4" 
(Stock 80")

BL Late 1981–'99 Stock Stock 1981–'99    
6 4 5⁄8" SL Late 1981–'99 S&S Stock 1981–'99    
9 Special Order SF 1999–up Press In Press In Press In    
12 5 1⁄4" SG S&S 4 1⁄8" Bore Press In   Press In    
13 3 1⁄2" 
(Stock 61")
SM 1995–'99 EFI Press In S&S 1981–'99    
14 3 31⁄32" (Stock 74") Y 74"/80" Indian® Stock Stock Stock    
16 5 1⁄8"              
17 4”              
18 3 5⁄8"              
19 4 1⁄8"              
TA 3 7⁄8” Titan Special             
TB 4.450”            

 


Flywheel Codes:

  • Codes that pertain to the most common regular production flywheels have been listed. Many other codes for racing flywheels and special orders also exist. If you have a question about a set of S&S flywheels with codes different than those shown, contact an S&S technical assistant to properly identify what you have.
  • Flywheel ID codes that end with an “A” or an “X” designate flywheels with a smaller than stock diameter. Stock big twin flywheels measure 8 1/2”, and stock flywheels for Harley-Davidson® Sportster® models are 7 7⁄8” in diameter. Typically, “A” means 1/8” smaller, and “X” means 1/4” smaller. To verify the code, it is best to measure the flywheels.
Flywheel Letter Codes


Serial numbers can be seen through the timing hole to identify the stroke of an assembled engine. Keep in mind they will appear upside down in the hole



  
S&S®  Flywheel Identification Codes for Harley-Davidson® Sportster® & Buell® Models
Stroke Code Stroke Year Code Engine Year Sprocket Shaft Pinion Shaft Crankpin Type Rod Bearing Type Diameter Code Flywheel Diameter
1 4 1⁄16" None 1957–'76 Stock Stock Stock Stock None 7 7⁄8" (Stock)
2 4 3⁄16" B
1957
Early '81
Stock Stock Stock Stock A 7 3⁄4"
3 4 5⁄16" SB
1957
Early '81
S&S Stock Stock Stock X 7 5⁄8"
4 4 7⁄16" BD 1957
Early '81
Stock   Stock Stock    
6 4 5⁄8" SBD 1977
Early '81
S&S   Stock Stock    
7 4 13⁄16" C* Late 1981–'85 Stock Stock  Stock Stock    
8 5" SC Late 1981–'85 S&S Stock Stock Stock    
9 Special Order SCD Late 1981–'85 S&S   Stock Stock    
11 4 1⁄2" SCR Late 1981–'85 S&S Stock Stock 1987-Up    
12 5 1⁄4" SCDR Late 1981–'85 S&S   Stock 1987-Up    
15 3 13⁄16” D Late 1986–’03 S&S S&S S&S S&S    
16 5 1⁄8" DR Late 1986–03 S&S S&S S&S 1987-Up    
17 4" PS S&S Prostock Press In Press In Press In      
18 3 5⁄8" KRS 45" WR/KR Stock Stock 1957-'81 XL 1957-'81 XL    
19 4 1⁄8" YS 45" Indian® Stock Stock Stock Stock    
      
*Obsolete – S&S no longer makes this design.