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Ironhead Top End Rebuild

Text and Pictures by Mark Trotta

Compared to the bottom end, rebuilding the top end of an Ironhead Sportster requires less time and less special tools.

Ironhead rocker box assembly

The two main obstacles will be if the cylinder jugs need boring and if the valve seats need to be cut. This is where careful inspection and measurement pays off. If you're lucky, you may get away with just honing the jugs and installing new piston rings.

Tools Needed To Rebuild Ironhead Top End

Aside from basic hand tools, you'll need a few engine rebuilding tools such as a piston ring installer, torque wrench, dial caliper, and feeler gauge. There are also a few specialty tools needed, although some of them can be fabricated.

Read: Ironhead Special Tools

Cylinder Boring And Honing

New cylinders, whether they are new or aftermarket, need to be accurately measured, bored, and honed. A good straight bore with a proper cross-hatch pattern, and correct piston to wall clearances, is a MUST for good sealing and ring life.

Motorcycle cylinder hone

Read: DIY Motorcycle Cylinder Boring

cast iron motorcycle cylinders

Read: Ironhead Sportster Cylinders

The cylinders in the picture above are for an 900cc Ironhead Sportster. They are painted the original factory silver.

Cylinder Heads

Ironhead Sportsters are named after their cylinder heads. Made from cast-iron, they're pretty durable and rebuildable up to a point. The biggest problem with these is the ham-fisted butcher who tried fixing it before you.

900cc Ironhead Sportster build

Read: Motorcycle Valve Job

rebuild motorcycle cylinder heads

Read: What Is A Three-Angle Valve Job ?

how to remove valve guides from cylinder head

Read: How To Remove Valve Guides

Ironhead engine rebuild and repair

Read: How To Install Valve Guides

Ironhead Sportster rocker box assembly

Read: Ironhead Rocker Box Assembly

Ironhead rocker box assembly

Read: How To Polish Aluminum Motorcycle Parts