Taking care of a Harley-Davidson bike means more than just changing oil. You need to know about its many bolts and screws. Knowing about these parts is key. It helps keep your bike safe. It also helps it run well and last a long time. Every part, from the engine to the frame, needs the right fasteners. You must pick and put them in correctly.
Harley-Davidson gives long lists of parts. They also have full repair guides. This shows how exact you need to be. If you are not careful with fasteners, parts can break. This can be unsafe. It can also cost a lot to fix. When Harley-Davidson gives such small details about fasteners, it means something. It means changing sizes, materials, or how tight they are can be risky. These risks are not just a loose part. They can cause big problems. This includes engine parts, brakes, or suspension. You must use new fasteners that are just like the old ones. They must be the same in size, type, strength, and rust proofing. This means each fastener is made for its job. It is not just a random part. So, for any Harley owner or mechanic, learning these details is a must. It helps you take good care of your bike. It makes knowing about fasteners a key part of keeping these famous bikes safe and working well.
Harley-Davidson’s Bolts: Old and New Styles
Harley-Davidson motorcycles use two main types of fasteners. They use both SAE (American) and metric systems. Knowing this mix is the first step for good and safe repairs.
Mostly SAE (American) Parts
For a long time, Harley-Davidson bikes used SAE sizes for their fasteners. This is part of American manufacturing. Sizes are in inches. Examples are 1/2″ and 9/16″. For bolts, this means the width is in inches. The threads are counted by how many fit in an inch. Washers and nuts also mostly use inch sizes. Their inner and outer sizes, thickness, height, and wrench sizes are all in inches.
Adding Metric Parts: Why and Where
Harley-Davidson still uses SAE parts. But newer bikes also have metric parts. These are often on parts from other countries. This includes electric parts, brakes, and other add-ons. Bikes sold outside the U.S. might have more metric parts. This is due to global making and new rules. Metric sizes are in millimeters. This is for width, thread spacing, and length. For example, you might see M8 x 1.0 x 18 hex head screws. Or M6 x 1.0 x 27 socket head screws (Grade 8). Also, M10 x 1.5 x 60 hex head bolts. A clear example is axle sizes. Sportster bikes from 2004 changed from 3/4 inch to 25mm axles. V-Rod bikes always use 25mm axles.
How Fasteners Changed Over Time
Harley-Davidson keeps changing. So, SAE and metric parts are used together. Older bikes mostly use SAE. Newer bikes mix both. Even old SAE bikes might have odd thread types. The change in axle sizes for Sportsters shows this. It means metric parts are slowly being used more. This is due to new tech and buying parts from all over.
Also, how fasteners are made and put in has changed. This fixes old problems. For example, early Evo engines (1985-1994) had soft head bolts. They would stretch. This caused gasket leaks. In 1995, Harley-Davidson made changes. They put cylinder studs in upside down. This stopped head bolts from hitting the bottom. It also made them hold tighter. This history shows that old repair guides might not have the best ways to fix things.
Using both SAE and metric parts on Harley-Davidson bikes can be tricky. Mechanics and owners need many tools. They must be careful to pick the right fastener. If you use the wrong tool or part, it can cause problems. Bolts can get stripped. Parts might not fit right. For example, a 1/4 inch SAE bolt is almost the same size as an M6 (6mm) metric bolt. If you try to use an SAE wrench on a metric bolt, it might seem to fit. But it can strip the bolt head. Or it can damage the tool.
Also, putting in a bolt with the wrong threads will cause harm. Even if the size looks close, like 1/4-20 versus 1/4-28, it will ruin the threads. This damage often means costly repairs. You might need special kits. Or you might need to replace the whole part. A good example is T27 Torx fasteners on Harleys. A T25 Torx tool might seem to fit. But it is a bit loose. It can easily strip the screw head. This means you need the right tools. You must also be careful to find the right part.
Older bikes can be even harder to work on. Finding the right fasteners can be tough. Some parts are no longer made. Some old thread types are rare. This means you need special knowledge. You might need old parts catalogs. Or you might need to find special sellers. Also, old repair guides for Evo engines did not say to change soft head bolts. They also did not say to put cylinder studs in correctly. This means just using an old guide can cause problems again. So, good mechanics must keep up with new info. They need to know about old problems and new fixes. This makes fixing bikes a smart process. It uses what we learn over time and from the maker.
How to Read Fastener Names and Sizes
Knowing a fastener’s size and type is key for good repairs. Harley-Davidson uses a clear system to name its bolts, screws, washers, and nuts. This helps everyone know what part is what.
How English (SAE) Bolts and Screws are Named
SAE bolts and screws are named by their main width. This is in inches or parts of an inch. Then comes the threads per inch (TPI). Last is the length of the threaded part, also in inches. For example, a “3/8-16 x 1-1/4” bolt means it is 3/8-inch wide. It has 16 threads per inch. This is a common coarse thread. It is 1-1/4 inches long. This system makes it easy to know a fastener’s size. You can see this in part lists like “1000 SCREW, 1/4-20 X 5/8 pan hd.”.
How Metric Bolts and Screws are Named
Metric fasteners start with an “M.” Then comes the width in millimeters. Next is the thread pitch. This is the space between threads in millimeters. Last is the length in millimeters. For example, an “M8 x 1.25 x 25” bolt means it is 8mm wide. It has a 1.25mm thread pitch. This is a common coarse thread. It is 25mm long. This metric system is clear. It is used all over the world. You can see examples like “1031M SCREW, M8 X 1.0 X 18 hex hd.” in part lists.
How Washers and Nuts are Sized
Washers are known by their inner size, outer size, and thickness. Nuts are known by the width and thread pitch of their hole. Also by their total height. And by their hex size. This is the distance between flat sides. These sizes are vital. They make sure parts fit right. They help spread weight. They also ensure your tools fit. Examples are an English “3/8-16 x 7/16 x 9/16 nut” and a metric “M8 x 1.25 x 7.25 x 15 nut”.
The detailed names for both SAE and metric fasteners are very important. They are not just for showing what a part is. They help keep things safe and working together. If you read any part of the name wrong, it can cause problems. The part might not fit. Threads can strip. Or it might not hold tight enough. This can harm the bike’s structure and safety. Being exact with these names is key. For example, a “1/4-20” bolt is not the same as a “1/4-28” bolt. Both are 1/4″ wide. But their threads are different. Trying to force a 1/4-20 bolt into a 1/4-28 hole will break the threads. This makes the connection weak. It cannot hold tight. It might break from shaking or weight. This is true for metric fasteners too. For example, M10x1.0 versus M10x1.25 versus M10x1.5.
Such damage often means costly repairs. You might need special kits. Or you might need to replace the whole part. This shows that “close enough” is not good enough for fasteners. You must look closely. Use thread gauges. Check with official papers. This makes sure parts fit perfectly. This directly affects how well and safely a repair works. This careful way of working is a sign of good maintenance.
Common Fastener Head Shapes and Tool Types
Harley-Davidson motorcycles use many types of fastener heads. They also use many tool types. Each is picked for a reason. This could be how it works, how easy it is to use, or how it looks. Knowing these types helps you pick the right tools. It also helps you tighten them correctly.
Head Shapes
Harley-Davidson uses many head shapes. They fit different needs. Common types are:
- Hex head: Used for general fastening. Good for high force.
- Torx head: Often used for safety. Good for higher force. Less likely to slip.
- Allen (socket) head: Good for tight spots. Looks clean.
- Pan head, button head, truss head, oval head, fillister head, carriage head, and 12-point head: Each has its own benefits. These include how much force it can take, how much room it needs, and how it looks.
Tool Types
Many tool types fit these heads. These include:
- Hex Socket
- Torx Socket
- Phillips
- Pozidriv
- Slotted
- Clutch
The tool type often depends on the force needed. It also depends on how much the tool might slip. And how easy it is to reach the fastener. Torx tools, for example, are known to transfer force better. They slip less than old Phillips or slotted tools. This makes them good for key connections.
Harley-Davidson uses specific head shapes and tool types, like Torx. This is not just a style choice. It is a smart engineering choice. It helps transfer force better. It stops stripping. And sometimes, it stops people from messing with parts. This means you must use the right, good-quality tool. This stops damage to the fastener and the part it holds. The T27 Torx tool is a good example. A T25 Torx might seem to fit. But it is “a little on the loose side and will strip the screw.” This is a key detail. It shows that these tool types are picked for how well they work. Using a tool that does not fit well will harm the fastener. It will round out the hole.
Stripped heads always make removal hard and slow. They can also damage nearby parts. You might need special tools to get them out. So, buying a full set of good tools is a must. This includes Torx bits, especially the less common T27. This is not an option. It is needed for good Harley-Davidson care. Such tools help fasteners last longer. They make future repairs easier. This saves time and stops costly damage.
Fastener Strength Grades: For Safety and Long Life
A fastener’s strength grade is very important. But people often forget about it. It tells you how much weight a bolt can hold. This is before it bends or breaks. This directly affects the bike’s safety and strength.
SAE Grade Types
Harley-Davidson often uses SAE Grade 5 fasteners. Stronger ones, like Grade 8, are used in key spots. These spots need extra strength. SAE bolts often have lines on their heads. More lines mean more strength. For example, Grade 5 bolts usually have three lines. They can hold at least 120,000 psi of pull force. Grade 8 bolts have six lines. They can hold at least 150,000 psi of pull force.
Metric Strength Classes
Metric fasteners also have strength levels. They are less common than SAE grades. They usually have two numbers. These are stamped on the bolt head (e.g., 8.8, 10.9, 12.9). The first number shows the pull strength. The second number shows how much it can bend before breaking. A higher number means a stronger bolt. Metric screws with Grade 9.8 are also listed. This means they are used in tough spots.
Why Using the Right Strength Grade is Key
Harley-Davidson uses SAE Grade 5 and Grade 8 fasteners. They also use metric Grade 9.8. This shows that Harley-Davidson designs specific fasteners for specific jobs. This means using a weaker bolt is very risky. Even if it fits, it can cause parts to break off. Or the structure can fail under stress. For example, if you replace a Grade 8 bolt (150,000 psi strength) with a Grade 5 bolt (120,000 psi strength), it will be much weaker.
Motorcycles shake and move a lot. They have engine vibrations, speed changes, and braking forces. A weaker bolt is more likely to bend, stretch, or snap. If a brake caliper bolt fails because it’s the wrong grade, you could lose your brakes. So, new fasteners must be just like the old ones. They must be the same in strength, material, and rust proofing. This is not just a suggestion. It is a must for safety. This means picking the right fastener is more than just size and threads. It also means picking the right material and strength. Mechanics and owners must be careful. They need to find fasteners with the correct strength grade. Look at the head markings. This keeps the bike strong and the rider safe. This is a very important part of good maintenance.
Harley-Davidson Bolt Sizes: Examples for Different Parts
This part gives examples of common bolt sizes. It shows where they are used on Harley-Davidson bikes. This list is just a guide. It is not a full list. Different models, years, and small changes can mean different sizes. Always check your bike’s service manual. It has the exact details for your motorcycle.
The detailed list of fasteners shows something. Harley-Davidson uses very specific fasteners for each part. This means fasteners are not just interchangeable. Even if they look similar, their length, head type, or threads are made for a certain spot. This helps the part fit and work best. For example, a 1/4-20 bolt might be used on both the cam cover and the primary. But their lengths are very different. The cam cover might use 2-1/4″. The primary might use 2″. If a bolt is too long, it might hit the bottom. It will not hold the part tight. This can make the part loose. Or it can damage the hole. If a bolt is too short, it might not grab enough threads. This can cause it to strip or break.
Also, the head type (like hex head or socket cap) is picked for how easy it is to reach. It is also picked for how much force it needs in that spot. This shows why you need the right service manuals and parts lists. Do not just guess. Do not think a bolt of the same width will work for different parts. This level of detail is a sign of good engineering. It means you must be just as careful when you fix things.
Common Harley-Davidson Fastener Examples by Part
| Application | Fastener Size | Head Type | Quantity (if specified) | Notes/Source |
| Crankcase | 5⁄16″x18x4½” | hex head bolt | 1 | 1000cc XL |
| Crankcase | 5⁄16″x18x4″ | hex head bolt | 1 | 1000cc XL |
| Crankcase | 5⁄16″x18x2½” | hex head bolt | 3 | 1000cc XL |
| Crankcase | 5⁄16″x18x3″ | hex head bolt | 2 | 1000cc XL |
| Oil Pump | ¼”x20x2″ | hex head bolt | 5 | 1000cc XL |
| Lifter | 5⁄16″x18x¾” | socket cap | 4 | 1000cc XL |
| Rear Motor Mount | 3/8x16x½” | hex head bolt | 2 | 1000cc XL |
| Rear Motor Mount | 3/8″x16x1″ | hex head bolt | 2 | 1000cc XL |
| Rocker Box | 5⁄16″x24x2¼” | hex head bolt | 12 | 1000cc XL |
| Rocker Box | 5⁄16″x24x1″ | hex head bolt | 2 | 1000cc XL |
| Cam Cover | ¼”x20x2¼” | socket cap | 2 | 1000cc XL |
| Cam Cover | ¼”x20x2″ | socket cap | 2 | 1000cc XL |
| Cam Cover | ¼”x20x1¾” | socket cap | 2 | 1000cc XL |
| Cam Cover | ¼”x20x1½” | socket cap | 1 | 1000cc XL |
| Cam Cover | ¼”x20x1¼” | socket cap | 1 | 1000cc XL |
| Primary | ¼”x20x2″ | socket cap | 8 | 1000cc XL |
| Primary | ¼”x20x1½” | socket cap | 2 | 1000cc XL |
| Primary | 10x24x1¼” | socket cap | 1 | 1000cc XL |
| Derby Cover | No. 8-32 X 1/2 | TORX SEMS pan hd. | – | General |
| Front Axle | 3/4 inch | – | – | Sportster 1957-2003 |
| Front Axle | 25 mm | – | – | Sportster 2004-Present, V-Rod 2002-2017 |
| Rear Axle | 1 inch | – | – | Sportster 1957-2003, Dyna, Softail, Touring |
| Rear Axle | 25 mm | – | – | Sportster 2004-Present, V-Rod 2002-2017 |
| Front Brake Rotor | 5/16-18 x 7/8 | Torx | – | 1984-2023 H-D |
| Rear Brake Rotor | 3/8-16 x 1 1/2 | Tapered | 5 | 1981-1984 FLH, 1979-1991 XL Rear (Laced Wheel) |
| Riser Bolt Kit | 1/2-13 x 2-3/4 | Hex | – | General |
| Drain Plug (Oil/Primary) | 1/2-20 Thread | Hex/Allen | – | 2000-2023 H-D Models |
| Drain Plug (Primary) | 3/8-24 Thread | – | – | 2004-2006 Softail, FLT Models |
| Cylinder Head/Base | 7/16-20 UNF | Acorn Nut | – | 1948-1984 B.T. Models |
| General Hardware | 1/4-20 X 5/8 | pan hd. | – | Example from listing |
| General Hardware | M8 X 1.0 X 18 | hex hd. | – | Example from listing |
| General Hardware | 5/16-18 X 2 | hex flange hd. | – | Example from listing |
Torque Specs: How Tight to Make Bolts
Tightening bolts correctly is very important. It keeps your motorcycle safe and working well. It makes sure bolts hold parts tightly. It stops them from being too tight. Too tight can stretch or break the bolt. It can also strip threads. Not tight enough can make parts loose. This can cause them to fail.
General Torque Values for Common Bolts (Grade 5)
You can find general torque values for common SAE Grade 5 fasteners. These are used a lot on Harley-Davidson bikes. These values are a good starting point. But always use the exact numbers from your bike’s service manual.
General Torque Values for SAE Grade 5 Fasteners
| Fastener Size | Torque Value |
| #8 | 14 inch-pounds |
| #10 | 22 inch-pounds |
| 1/4″ | 10 foot-pounds |
| 5/16″ | 19 foot-pounds |
| 3/8″ | 33 foot-pounds |
| 7/16″ | 54 foot-pounds |
| 1/2″ | 58 foot-pounds |
| 9/16″ | 114 foot-pounds |
| 5/8″ | 154 foot-pounds |
| Source: |
Always Use Your Bike’s Service Manual
General charts are helpful. But your Harley-Davidson factory service manual is the best source for torque values. It has exact numbers for your bike’s model and year. These manuals often show how to tighten bolts in a certain order. For example, a star pattern for engine bolts. They also have notes for key parts. They consider different materials and designs. If you do not follow these rules, parts can bend. Fluids can leak. Or parts can break completely.
Knowing exact torque values is key. So is using threadlockers and anti-seize. This shows that putting fasteners on a Harley-Davidson is a careful process. It is not just “tightening until it feels right.” If you ignore these details, parts can wear out fast. They can break. Or they can even fall off. Bikes shake a lot. So, if a bolt is not tight enough, it can come loose. This can cause noise. It can cause wear. Or the part can fall off. If a bolt is too tight, it can stretch. It can strip threads. Or it can crack the part. This harms the connection for good.
The “star pattern” for engine bolts is very important. If you do not use it, the parts might not be held evenly. This can cause bending or leaks. If threadlocker is needed but not used, bolts can back out. Using the wrong type, like red Loctite instead of blue, can make it very hard to take apart later. You might even need to drill out bolts. So, tightening a bolt is not just a simple act. It is a precise step. It affects how reliable, safe, and easy to fix your bike will be.
There is a small but important detail. Torque is measured in inch-pounds and foot-pounds. You need two different torque wrenches for this. One for low force. One for high force. This means you need to be exact for all torque levels. Many small fasteners, like on engine covers, need very low torque. This is often in inch-pounds. For example, 80 in-lbs for the derby cover. Or 70-80 in-lbs for oil pump screws. A large foot-pound wrench is for high torque. It will not be exact for low inch-pound values. Its inside parts are not sensitive enough. Tightening small fasteners too much is a common mistake. It happens with the wrong wrench. This often strips threads or breaks bolts. These are hard and costly to fix. This means serious Harley-Davidson care needs special, exact torque tools. They must cover all fastener sizes and torque needs. It is not just about having
a torque wrench. It is about having the right torque wrench. This shows that being exact and having special tools is key for good maintenance.
Using Threadlockers and Anti-Seize
Beyond torque, using chemicals like threadlockers and anti-seize is vital. Threadlockers, like blue Loctite, stop bolts from loosening due to shaking. This is common on bikes. Red Loctite is for more permanent use. Anti-seize is used on exhaust bolts. It stops parts from sticking or rusting. This makes it easier to take them apart later. This is true for hot areas. These chemicals are a key part of good fastener care on a Harley-Davidson.
Tools You Need for Harley-Davidson Care
Working on a Harley-Davidson bike well means more than just knowing bolt sizes. You need a special set of tools. Buying the right tools helps your bike last longer and be more reliable.
SAE Wrenches, Sockets, and Allen Keys
Harley-Davidson mostly uses SAE fasteners. So, you need a full set of SAE wrenches. These include open-end and box-end. You also need sockets. Sizes range from 1/4″ to 1″ and larger for some parts. For example, primary nuts can be 13/16″ to 1-3/8″. Allen (hex) keys are also key. They are usually in SAE sizes, from 3/32″ to 3/8″. It is good to have them in different lengths. Short and long. Also, ball-end types help reach tight spots.
The Important T27 Torx Bit
Torx fasteners are everywhere on newer Harley-Davidson bikes. You find them on engine covers, controls, and other parts you can see. The T27 Torx bit is very common. But it is often missing from basic tool sets. These sets might skip from T25 to T30. This makes the T27 a must-have. It stops you from stripping fasteners. A T25 might seem to fit. But it is a bit loose. It can easily damage the screw head.
Getting Good Torque Wrenches (Inch-Pound and Foot-Pound)
As we said, using the right torque is vital for safety. It also stops damage. So, you need to buy at least two good torque wrenches. One for lower inch-pound values. This is for small bolts and sensitive parts. Another for higher foot-pound values. This is for bigger, key bolts like axle nuts or engine mounts.
Other Special Tools and Supplies
You might need other special tools. This depends on how much work you do. This includes metric tools for some parts. Especially electric parts or parts from other countries. For example, a 10mm wrench for battery terminals. Impact sockets and air wrenches can help with tough bolts. A long 6mm impact socket is needed to take apart fork legs. A vacuum brake bleeder helps change brake fluid.
You will also need some supplies. These include different threadlockers. Blue Loctite for most bolts. Red Loctite for stronger, more lasting hold. Anti-seize for hot parts like exhaust bolts. This stops them from sticking. Gasket sealants like Gasgacinch are also useful. A good volt/ohm meter is key for checking electric parts. Tools to remove broken bolts are also good to have.
The long list of tools shows something. Serious Harley-Davidson care is a special job. It needs a big investment in tools and knowledge. This means trying big repairs with few tools will likely cause damage. It will cause frustration. And it will cost more. The mention of “specialty HD tools like seal and bearing pullers and installers” means some jobs need special tools. They also need the right skills to use them. The warning about the T27 Torx and the T25 shows that even small tool errors can cause big damage. This includes stripped bolt heads. This makes future work hard or impossible without breaking parts. This means for anything more than oil changes, owners should do one of two things. They should buy many tools and keep learning. This includes getting the must-have factory service manual. Or they should use skilled mechanics. This shows that Harley-Davidson care needs the right tools and know-how. This directly affects how good, safe, and long-lasting the work will be.
FAQs about Harley Davidson Bolt Size Chart
- What types of fasteners does Harley-Davidson use? Harley-Davidson motorcycles use both SAE (American) and metric fasteners. This mix means you need tools for both types. Knowing this helps with repairs and finding the right Harley Davidson bolt size.
- Why is knowing the correct Harley Davidson bolt size important? Knowing the right Harley Davidson bolt size is key for safety and good repairs. It helps parts fit well. Using the wrong size can strip threads or cause parts to fail. This can lead to costly damage.
- What are common Harley Davidson bolt head types? Harley-Davidson motorcycles use many bolt head types. Common ones include hex, Torx, and Allen heads. Each type needs a specific tool for proper use. This helps prevent damage to the Harley Davidson bolt.
- Where can I find specific Harley Davidson torque values? Always check your Harley-Davidson factory service manual for exact torque values. These manuals give precise numbers for your specific model and year. This ensures safe and proper tightening of every Harley Davidson bolt.
- Do I need special tools for Harley Davidson fasteners? Yes, you need special tools for Harley Davidson fasteners. A full set of SAE wrenches, Torx bits (especially T27), and two torque wrenches are key. These tools help you work on any Harley Davidson bolt.
- How do Harley Davidson bolt sizes change over time? Harley Davidson bolt sizes have changed over time. Older models mostly use SAE. Newer models mix SAE and metric. Axle sizes, for example, have shifted from inches to millimeters on some models.
Final Words
Knowing how to handle Harley-Davidson fasteners is a key part of owning one. It helps you take good care of your bike. It needs a careful way of working. It needs exact tools. And it needs correct information. By following good rules, your bike will be safe. It will run well. And it will last a long time.
Key tips for good fastener care:
- Know Both Systems: Harley-Davidson bikes use both SAE and metric fasteners. So, you need a tool kit that has both. Some SAE and metric sizes are very close. You must be careful to tell them apart. This stops damage.
- Find the Right Part: Always know the exact size of the fastener. This includes its width, threads, length, head shape, and most important, its strength grade. “Close enough” is never okay. Wrong parts can strip threads. They can hold parts too loosely. Or they can cause big failures.
- Torque is Key: Tightening bolts correctly is a must for safety. It also stops parts from breaking. This often means tightening them in a certain order. If you tighten too little or too much, parts can loosen. They can bend. Or bolts can break. This harms the bike’s strength.
- Special Tools: You need to buy good, exact tools. This includes a full set of Torx bits. The T27 is very important. You also need both inch-pound and foot-pound torque wrenches. This ensures exactness for all fastener sizes and torque needs.
- Check the Manual: The Harley-Davidson factory service manual for your bike is the best source. It has all fastener details, torque values, and how-to steps. Many sources say to use this manual for torque and steps. This shows how vital it is. This advice means no general chart can replace your bike’s manual. The manual has special, detailed, and often updated info. This info is key for exact and safe care. Just using general info can be risky. This is because fastener types, materials, and torque needs change by model and year. This means you should always use the main, exact source for your bike. This helps you care for your bike safely. It helps you follow the maker’s rules. This lowers risks. And it helps your bike last as long as possible.