Classic Motorcycle Build

How To Adjust Ironhead Valves

Text and Pictures by Mark Trotta

Through normal use and wear, engines with solid lifters require periodic adjustment. If your Ironhead Sportster is not starting or running poorly, it could be the valves are not fully opening or closing.

how to adjust Ironhead valves

What Is Valve Clearance?

All Sportsters have four cams, located in the right-side engine case. Above each cam is a lifter (also called tappets) which sit below each of the four push rods. Valve clearance is the space between the top of the lifter and the bottom of the push rod.

Why Valve Clearance Is Important

If a valve doesn't have enough clearance, it doesn't fully close. This allows some compression to escape through one or both valves. Aside from losing power, the affected valve(s) may become overheated.

adjust Ironhead pushrods

If a valve has too much clearance, it doesn't fully open. This robs the engine of power.

Getting Started

Mechanically, Ironhead Sportsters remained much the same through their long 26-year production run. All years and models have solid lifters. Adjusting valves on a late 50's or early 60's bike is the same as on 70's and 80's bikes.

Do I Need A Work Stand?

Having a motorcycle lift stand is a great time (and back) saver, but most Ironhead maintenance can be done "old school" (you crouched on the floor).

Valve clearance is measured when the engine is cold, and when each lifter is at it's lowest point (when that particular valve is closed).

Adjusting valves requires slowly turning the flywheels, which turns the cams, which moves the lifters into the up or down position. The engine will need to be rotated approximately 6-12 times during the valve adjustment procedure. There are several ways to do this.

Method One: If your bike has a kick-start, you can turn the motor over with the kick pedal.

TIP: Rotating the engine is much easier with the spark plugs removed.

Method Two: For non-kick start bikes, you can raise the rear wheel off the ground an inch or two, then with the bike in gear, turn the rear tire by hand. This will allow you to slowly move the flywheels/cams/lifters.

Method Three: On the 1981 Sportster in the pictures, the motor is a fresh rebuild, and I'm purposely adjusting the valves before re-installing the clutch cover. This allows access to the front motor sprocket nut.

how to adjust Ironhead Valves

Turning the sprocket nut rotates the flywheels/cams.


Push Rod Cover Removal

If you've worked on an Ironhead Sportster before, you know there are plenty of specialty tools. Before I had the proper tool, I was using a screwdriver to hold down the push rod tube with one hand, then trying to remove the spring cover with the other hand while under tension. If they are not under considerable tension, the inner tube springs may be worn, which would allow oil leakage.

remove pushrod covers on Ironhead Sportster

If you're not super careful, the screwdriver will slip and scratch the chrome covers.


Push Rod Cover Tool

The Motion-Pro push rod tool removes and installs push rod tube clips with no hassle. The flat portion of tool fits under the cylinder head, and the cupped end fits over the bell in the tube.

Motion Pro tool 08-0255

Shop: Harley Push Rod Cover Tool

Motion Pro pushrod tube tool for Harley

When you squeeze the tool, the spring compresses, and allows easy access to the spring cap retainer.

Installation is just as easy.

Push Rod Cover Hangers

You'll need a way to hold up the lower tubes up and out of the way while checking and adjusting valve clearance.

adjust Ironhead Valves

Lengths of heavy mechanic's wire bent to shape work just fine.

Ironhead Sportster tappet adjustment

You'll also need 7/16" and 1/2" open-end wrenches.

Ironhead pushrod adjustment


Pushrod Tube Seals

Before starting the tappet adjustment procedure, check the tube seals. This is the time to replace them.


Valve Adjustment Procedure

The following is essentially the method laid out in the factory service manual, plus a few tips we've come across over the years. Remove the spark plugs so the motor turns over easily. Removing the air filter may give you some extra work room.

Turn the engine slowly and watch how the lifters move. After you do this several times, you can anticipate when the cams/lifters will go up and down.

Intake valves are those nearest to the carburetor, exhaust valves are furthest. When a tappet is fully open, the corresponding tappet on the other cylinder will be fully closed. For each tappet you adjust, you want it fully closed (at it's lowest position).

tappet adjuster screw and nut Harley Ironhead Sportster

Feel for 'up and down' play in the push rod with your thumb and index finger. The push rod should turn right to left (back and forth) smoothly with no binding.

Adjust Intake Valves

When the front intake valve is fully open, the rear intake can be checked/adjusted. When the rear intake valve is fully open, the front intake can be checked/adjusted.

Adjust Exhaust Valves

When the front exhaust valve is fully open, the rear exhaust can be checked/adjusted. Then, when the rear exhaust valve is fully open, the front exhaust can be checked/adjusted.

Tappet Adjuster Screw and Nut

If there is too much play, loosen the bottom tappet adjusting screw lock nut, then turn the adjusting screw towards the push rod until it's gone.

how to adjust Ironhead push rods

When correctly adjusted, the push rods rotate freely with any binding. There will be no up-down or side-to-side movement.

NOTE: If an exhaust valve is adjusted too tight, it could burn a valve. For this reason, some tuners leave the exhaust slightly loose.

how to check valve clearance Harley Sportster

When satisfied with the results, tighten the lock nut. The factory torque spec is 8-10 ft/lbs against the tappet body, but most techs just use their own good judgment.

NOTE: The lock nuts purposely have a cut in them. They are commonly called 'split nuts', and they help prevent the nuts from loosening.


Problems With The Lock Nut and Threaded Screw

Sometimes you'll find a lock nut that isn't turning freely, or binds in one spot. Sometimes a lock nut gets wrenched up too tight against the flared, unthreaded portion of the adjuster screw, and won't come loose.

If for any reason all the lock nuts don't thread up and down easily on all the adjuster screws, the best thing to do is replace them.

If you need to replace only the split lock nuts you can buy them here.

lifter adjuster screw nut kit Harley 18570-38

To buy an Ironhead Tappet Screw and Nut Set click here.

After you've adjusted the push rod play and tightened the lock nut, check it once again as it sometimes changes.


Re-Install Push Rod Covers

When reinstalling the pushrod covers, make sure that the upper tubes are seated into the bottom of the cylinder head.

Ironhead Sportster pushrod adjustment procedure

If they aren't, you'll never get the pushrod covers back on!

how to adjust Ironhead Sportster Valves

If you're missing pieces, you can buy a pushrod cover kit here.


How Often Should Ironhead Valves Be Adjusted?

The factory service manual states that Ironhead valve adjustment should be done after 500 miles of initial engine break-in, then at 1,000 miles, and every 2,000 miles thereafter.


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Read: Best Carburetor For Ironhead Sportster