Ironhead Valve Job
Text and Pictures by Mark Trotta
Properly rebuilt cylinder heads will make your Ironhead Sportster start easier, run smoother, and restore lost power.
First-time builders will quickly learn that new replacement heads are simply not available. That leaves four choices:
Find a good used, less worn-out pair.
Find a freshly rebuilt pair.
Pay someone to rebuild yours.
Tackle the job yourself.
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Cylinder Head Removal
Regardless of which way you choose to go, the heads have to come off. This will include exhaust pipes, carburetor and intake manifold, pushrod covers and pushrods.
Read: Ironhead Cylinder Head Removal
Removing Rust and Corrosion
After removing the springs, collars, and valves, removing rust and corrosion from hard to get to places can be done by hand with Emory cloth, but an electric rotary grinder get it done in a fraction of the time.
Read: Rotary Shaft Tool Review
Read: Ironhead Cylinder Head Cleaning and Inspection
NOTE: If you have several bad valve seats, worn valve guides, broken fins, and stripped threads, it's best to find a replacement head.
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Do It Yourself?
You won't know how much work or what parts are needed until the heads are off and valves are out. And will you be able to tell what parts are re-usable?
Once disassembled, factor in the cost of any parts needed. This may include intake and exhaust valves, springs, guides, seats, and a gasket set. The good news is that all these parts are still available.
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Tools Needed
If you're considering doing it yourself, you'll need a few specialty tools, and in the process learn some new skills. Besides basic hand tools, you'll need a valve spring compressor and a couple valve guide punches. You may also need a couple of guide reamers.
Shown: 3/8", 11/32", and 5/16" punches.
Refacing Valve Seats
There are several ways to overhaul valve seats. Being a one-man shop, I prefer Neway valve seat cutters.
You don't need to buy a complete set--you can buy only the cutter sizes for the job at hand, then purchase additional cutters when needed.
Valve Angle Cut
The use of three-angle seats in cylinder heads has been an industry standard for decades. This is done by having 'relief' angles above and below a 45 degree center contact surface.
Read: What Is A Three-Angle Valve Job ?
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Valve Guides
On Ironhead cylinder heads, worn guides are usually pressed out and new ones pressed in. Aftermarket guides are readily available in standard and oversize.
Read: How To Remove Valve Guides
Cast-Iron vs Bronze Guides
Bronze guides are self-lubricating and are less likely to gall than cast-iron guides. There are several derivatives of the bronze guide, which include phosphor bronze and manganese bronze.
Bronze guide on left, cast-iron guide on right
All bronze-based guides are better at dissipating heat than cast-iron guides--nearly twice as fast. But for a street-driven bike that may see an occasional high RPM blast every now and then, cast-iron guides are fine and will probably last as long as other engine components.
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Late Ironheads
1957 through early 1983 Sportsters have shouldered valve guides. An exception to this is mid 1983 to 1985 models, which were factory-installed with shoulderless guides.
Installing shoulderless guides requires either a special tool or very precise measurements.
NOTE: Valve Springs For Harley Sportster 1983-1985 are also different than earlier models.
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Valve Guide Installation
Once you have the cylinder head stripped down and cleaned, and have selected the proper replacement guides, you need a place to heat up the head safely.
By heating the metal, the new guide has an easier time going in. You only need to warm up the head somewhere between 200-250 degrees.
Read: How To Install Valve Guides
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Honing New Guides
After new guides have been installed, they need to be reamed to the proper size. This is because the valve guide I.D. usually distorts after being installed.
To properly hone a new valve guide, slowly run a precision reamer through it.
CAUTION: Skipping this step may cause valves to bind when the engine warms up and metals expand.
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Remove Valve Seats
Heating the heads with a hand-held torch or putting them in an oven (low temp) will help get the valve seats out. Another way is to weld a bead on the old seat, and the heat will (usually) cause the seat to shrink and fall out.
Valve Seat Specs
Intake: 2.068" x 1.750" x .315"
Exhaust: 1.757" x 1.371" x .315"
Oversize intake valve seats are 2" x 1.687 x 9/32" and can be used with unleaded gas.
Install Valve Seats
New seats are pressed in, but this best left to a competent machinist.
If you have no-one local that will do this, there are several places you can ship them to. Contact me for up-to-date info on this.
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Valve Springs
Valve springs should be replaced if damaged, or if old one is 1/8" or shorter than a new spring.
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Add Valve Stem Seals?
Prior to Evo models, Sportsters did not have valve stem seals from the factory, which means they'll always burn a little oil. Adding seals to the intake side helps the most, since intake valves tend to 'suck' mixture in. Seals are not as important on the exhaust side.
IMHO, this is not a necessary modification.
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Valve Lapping
When valves and seats are new, or in good condition, the lapping process is quick and easy.
After valve is lapped in, you're looking for a uniform and unbroken 'ring' around the valve.
Read: How To Lap Motorcycle Valves
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Paint Cast-Iron Heads
Applying a few coats of paint provides protection as well as good looks. To get paint to stick to a cast-iron, get it clean and dry.
These early 900cc heads were treated to a few coats of Duplicolor silver engine paint.
Cylinder heads drying outdoors on a hot sunny day.
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Reassembly
Apply a light coat of oil to valves, seats, and stems.
Note that there are upper and lower valve spring collars. Install lower valve spring collar over valve guide.
Install inner and outer spring.
Install upper collar.
NOTE: Valve Spring Collars For 1983-1985 Sportsters are different than earlier years.
Compress valve springs with valve spring tool.
Position two keepers on top of upper collar.
TIP: Coat the top of valve with wheel bearing grease. It holds the keepers in place.
Slowly release valve spring tool.
The keepers will either fall away or hold!
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900cc Ironhead Valve Job, before and after
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Top End Gasket Kit
James Gaskets are simply the best gaskets available for your old Harley. Their top-end gasket kit replaces H-D 17030-72 and includes everything you need to re-seal 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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Rocker Box Rebuild
Read: Ironhead Rocker Box Assembly
Read: How To Polish Aluminum Motorcycle Parts
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