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.

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.

Read: DIY Motorcycle Cylinder Boring

Read: DIY Motorcycle Cylinder Honing

Read: Ironhead Sportster Cylinders

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

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Top End Gasket Kit

Simply the best gaskets available for your Ironhead, the James Gasket Top End Gasket Kit replaces H-D 17030-72, and includes everything you need to reseal your top end.

Shop: Ironhead Top End Gasket Set 1973-1985

This top end gasket set includes copper head-gaskets, oil seals, O-rings, and all other gaskets necessary to completely rebuild an 1973 through 1985 Ironhead top end. James Gaskets are proudly made in USA.

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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 often caused by the ham-fisted mechanic who tried fixing it before you.