S&S Cycle Combustion Chamber Modification Instructions (Late Chamber) - Manual (Page 2)

Harley-Davidson ® Evolution ® Sportster ® models with a
displacement of 883cc’s require a combustion chamber
modification when installing an S&S
® 3-1⁄2” engines with a
displacement of 883cc’s require a combustion chamber
modification when installing an S&S 3-1⁄2” Bore Piston Kit. To
perform this modification do the following steps:
1. Carefully cut blackened center chamber section and head
line up dowel holes from cardboard template.
2. Paint head gasket surface on both heads to be modified with
machinist’s blue.
3. Place template on gasket surface and scribe line around
inside diameter of template as shown in Picture 1. Proposed
chamber area should look like head in Picture 2.
4. Assemble heads with worn out valves so that valve seats are
protected when grinding.
5. Carefully grind material inside scribed line away so that
chamber is somewhat spherical in shape. See Picture 3.
NOTE - Avoid grinding and contact on head gasket surfaces.
Grinding on head gasket surfaces will make an uneven
surface possibly causing lose of cylinder to cylinder head
gasket seal.
6. Polish chamber surface as desired. See Picture 4 for finished
product.
2
CAUTION
Picture 1 Picture 2
Picture 3
Picture 4