Safely Replace the Fasteners on Your Motorcycle – Understanding Bolt Grade

This is a short and sweet post covering a critical issue – how to safely replace the fasteners on your motorcycle.  This post makes me VERY nostalgic for my first motorcycle, which was a used (non-running) 1981 Kawasaki KZ440 (see the About Us page for more of that story).

To be honest, I basically had no money at the time, so I had no business buying a broken down motorcycle (I also described it to my parents as a “large scooter,” so that they wouldn’t freak out about my dive into the world of two wheels).

Anyways, I scraped together the $400 cash necessary and pushed the motorcycle home the two miles to my apartment.  I loved that bike and spent all my free time fiddling with it.  Given my cash flow problems, most of my subsequent “restoration” consisted of applying a lot of elbow grease and replacing rusted out old fasteners.  Being new to motorcycles, it was a good exercise.  Spending that much time combing over the bike front-to-back, got me very familiar with my machine.  Also, bolts are a relatively cheap item and it made me feel good giving my girl a few shiny new pieces.

Now, to the question underlying this post.  How do you safely replace the fasteners on your motorcycle?  The bottom line is that this comes down to bolt strength.  Don’t let anyone tell you that you have to buy OEM bolts from the manufacturer or some aftermarket item from a motorcycle website.  These will be extremely overpriced.  You CAN use your local hardware stores or online retailers provided you match or exceed the existing bolt grade.  Bolts come in various grades.  Sure, we could go into the technical specifications of each grade, but the bottom line of what you need to know is that lower grades are suitable for things like building wood furniture, while higher grades are suitable for high stress applications like motorcycles.

You generally can’t go wrong with a Grade 8 bolt.  These can be found at Ace Hardware, Home Depot, and Lowes if you are willing to look.  I love Ace Hardware.  Again, this is partly nostalgia, as this is where I sourced most of the bolts for my KZ440; but also, I think they have the best selection.  The telltale mark of a Grade 8 bolts is 6 radial lines on the head.

Safely Replace the Fasteners on Your Motorcycle

Example of Grade 8 Bolt Head

A Grade 5 bolt (three radial lines) will be good for many cosmetic applications on the bike, but the price difference between a Grade 5 and a Grade 8 should be negligible.  Therefore, to safely replace the fasteners on your motorcycle, I would stick to Grade 8 wherever possible.  The only issue is that it might be harder to find a good variety of Grade 8 locally.  Below are two websites I recently found that seem to have nice selections.  I actually ordered 180 Grade 8 bolts from Fastenal recently to replace the crappy hardware installed by my home builder on my hurricane shutters.


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I have tried to find a good reason online for why a Grade 8 bolt should not be used.  I found one or two websites that state they are more brittle.  This is simple not true if you look at the technical specifications.  I guess you should also consider corrosion resistance.  However, generally as you get into the higher grades of metric and SAE fasteners (by the way the equivalent of Grade 8 for metric is Grade 10.9, where the 10.9 will be stamped into the head), they are plated in such a way as to prevent corrosion making this a non-issue.

And whatever you do, DO NOT replace a Grade 8 bolt or any bolt on the bike with a lower grade bolt!!  This is very dangerous and could cause the bolt to break during riding. 

That’s it folks.  You now know how to safely replace the fasteners on your motorcycle.  Also, please please please, share this post via social media!  HappyWrench is new and needs your support!

Didn’t find what you needed in this particular post?  Check out the HappyWrench Motorcycle Repair Link Database.  It is a one-stop shop for all your DIY motorcycle repair information needs.

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