5 Things to Check Before Buying Used Harley-Davidavidson Engine Parts

Buying a used Harley engine part is a little different than buying a used brake pedal.

If the pedal has good threads, isn't bent and looks decent, you're probably in business.

A set of cylinders, crankcases, heads or a complete lower end?

That's where things get more interesting.

Harley has changed engine designs, dimensions, part numbers and internal components plenty of times over the years. Add 30, 50 or even 80 years of previous owners into the equation and you've got plenty of opportunities to buy something that looks right but isn't.

So before dropping money on a used Harley engine or engine part, here are five things we'd check.

1. Understand the Year, Engine Size and Changes

One of the biggest mistakes you can make is assuming:

“It's a Shovelhead part, so it'll fit my Shovelhead.”

Not necessarily.

Harley made plenty of changes inside each engine generation.

Take the Shovelhead as an easy example.

If you're working on a 1976 Shovelhead, you're normally dealing with the 74 cubic-inch version. The 80-inch Shovelhead started appearing later: Harley's own model history lists the FXS 74 through 1979½, with the FXS 80 beginning in 1979½, while other models made the switch on different timelines.

So when somebody has a random set of Shovelhead cylinders sitting on a swap-meet table, don't stop at:

“Yep, those are Shovel cylinders.”

You want to know:

• What year range?
• 74" or 80"?
• Standard bore or already bored oversize?
• OEM or aftermarket?
• What are the casting or part numbers?
• Have they already been machined?

That same logic applies to Evos, Sportsters, Twin Cams and Milwaukee-Eights.

Engine family gets you in the neighborhood. Year, model, measurements and part numbers get you to the right house.

2. Check Crankshaft / Pinion Runout Whenever You Can

If you're buying a complete engine, lower end or flywheel assembly, checking runout can tell you quite a bit about what you're buying.

You're basically checking how true the crankshaft is as it rotates.

This becomes especially important on Twin Cams when you're working around the cam plate, oil pump or considering gear-drive cams.

The basic test is straightforward:

Mount a dial indicator against the appropriate pinion-shaft surface and rotate the crankshaft through a full revolution.

The difference between the highest and lowest readings is your total indicated runout — TIR.

But here's an important point:

There isn't one magic Harley runout number for every engine Harley ever made.

Knuckleheads, Panheads, Shovelheads, Evos, Twin Cams and Milwaukee-Eights span almost a century of engine design.

The acceptable measurement can depend on:

• Engine generation
• Model year
• Where you're measuring
• Stock vs. aftermarket components
• Whether you're installing gear-drive cams
• The manufacturer's specification for the parts you're using

For example, S&S specifies 0.003" TIR or less at the pinion shaft for its 1999–2006 Twin Cam gear-drive cam chest installation.

S&S also sells crank assemblies trued to extremely tight tolerances — one of its later Twin Cam assemblies is advertised at less than 0.0005" runout on the shaft bearing surfaces.

That doesn't mean every used Harley crank showing more than .0005" is junk.

It means:

Know what you're measuring and know the specification for the engine and parts you're working with.

We'll make a separate guide specifically for checking Harley crankshaft runout by engine generation, because that deserves more than one paragraph.

For a used engine purchase, though, if the seller will let you put an indicator on it:

Do it.

Five minutes with a dial indicator can potentially save you a much more expensive surprise.

3. Pay Attention to the Engine Numbers

Image Source: Jockey Journal

This one isn't just about determining what year an engine is.

On vintage Harleys, those numbers can become part of the paperwork conversation too.

Before the 1970 model year, Harley identification centered around the engine serial number.

Then things changed.

Harley issued a service bulletin in September 1969 explaining that beginning with the 1970 model season, the company would stamp the same new Vehicle Identification Number on both the engine and frame.

That means you shouldn't repeat the common statement that Harley didn't start frame VINs until 1971.

1970 is the important changeover year.

Later, beginning with the 1981 standardized VIN system, Harley moved to the familiar 17-character motorcycle VIN, with the motorcycle primarily identified by the frame while the engine carries its own abbreviated identification.

So if you're buying:

• Knucklehead cases
• Panhead cases
• Early Shovelhead cases
• A complete vintage engine
• A questionable “matching numbers” bike

look closely at those numbers.

Check for:

• Grinding
• Welding around the number boss
• Strange fonts
• Uneven characters
• Obvious restamping
• Numbers that don't make sense for the claimed year
• Cases made from mismatched halves

And if you're building a titled motorcycle around vintage cases, check your state's current requirements before spending a pile of money.

A $4,000 set of beautiful vintage cases isn't nearly as exciting when the paperwork becomes a nightmare.

4. Know the Common Parts That Look the Same — But Aren't

Harley is extremely good at producing parts that make you say:

“Those look exactly the same.”

...right before you discover they aren't.

A perfect example is the Twin Cam A vs. Twin Cam B.

The Twin Cam B uses an internal balancing system. Harley's factory parts information shows separate front and rear balance shafts, a chain drive, tensioner system and other dedicated Twin Cam 88B components.

You typically see:

Twin Cam A

• Rubber-mounted applications
• Touring and Dyna families
• No internal balance-shaft system

Twin Cam B

• Primarily Softail applications
• Rigid-mounted engine
• Internal balance shafts

So when somebody lists something as:

“Harley Twin Cam engine part”

you may need considerably more information.

And Twin Cam A vs. B isn't the only trap.

Other common examples include:

• 74" vs. 80" Shovelhead components
• Early vs. late Twin Cam cam-chest parts
• Different Sportster 883 and 1200 components
• Carbureted vs. EFI intake parts
• Different cylinder-head chamber sizes
• Different bore sizes
• Early vs. late oil pumps
• Different crankcase configurations
• Parts that changed in the middle of a model run

This is where part numbers, casting numbers and actual measurements become your best friends.

When we're buying mystery engine parts, the calipers come out pretty quickly.

5. Remember — It's Still a Used Engine Part

This might be the most important one.

A seller can be completely honest with you and still not know everything about the part they're selling.

Maybe they bought the engine in a box.

Maybe they pulled the heads off a project 10 years ago.

Maybe the cylinders came in a parts lot.

Maybe the previous owner told them:

“Motor ran great when parked.”

We've all heard that one.

A used cylinder can look good and still need machine work.

A head can look perfectly clean and still need guides, seats or a valve job.

A crank can spin smoothly by hand and still show excessive runout once you put an indicator on it.

Cases can hide repairs.

Threads can have old Heli-Coils.

Cylinders can already be bored .060" over even though nobody mentioned it.

That's why inspecting used engine parts is about reducing risk, not magically eliminating it.

Some of the things we look for include:

• Cracks
• Weld repairs
• Damaged threads
• Broken fins
• Gasket-surface damage
• Rust or water intrusion
• Cylinder scoring
• Bore size
• Previous machining
• Bearing play
• Crankshaft runout
• Cam-lobe wear
• Valve-guide condition
• Casting numbers
• OEM part numbers
• Signs of overheating

And sometimes the only way to know exactly what you've got is to clean it, measure it and tear it down.

That's part of buying used engine components.

Used Doesn't Mean Bad

There's a huge difference between:

Used

and

Used up.

A good set of OEM Harley cases, heads, cylinders or other engine components can have plenty of life left in them.

And depending on what you're building, buying used OEM components can save a serious amount of money compared with purchasing everything new.

You just need to know what you're looking at.

So before handing somebody cash for that mystery engine sitting under their workbench:

Check the year.

Check the numbers.

Measure what you can.

Know the common interchange mistakes.

And assume there could still be something you don't know.

That's used Harley parts.

And to us, that's half the fun.

Looking for Used Harley Engine Parts?

Skyway Cycle Supply stocks used OEM and aftermarket Harley-Davidson parts ranging from vintage bikes through modern Harleys.

If you're not sure what you're looking at, send us the part number, measurements and a few pictures.

We spend an unhealthy amount of time identifying old Harley parts anyway.

Might as well put it to good use.

SHOP HARLEY PARTS HERE