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Harley Davidson Second Time Spark Plug Thread Repair

Harley Davidson Second Time Spark Plug Thread Repair

We have a short article called "Harley Davidson Spark Plug Threads - How to Fix" on spark plug thread repair kits used for first time repairs on Harley Davidson and other makes of motorcycles that has received a lot of attention lately. We've also been getting emails and phone calls on how to make a repair after a parts store insert has failed making the hole bigger. For second time repairs on M14x1.25 there's a Big Sert kit available. Big Sert is Time Sert's name for an oversize thread repair kit. It accepts the original size spark plug but uses a thicker repair insert so that it is capable of doing repairs when a thinner parts store type insert has failed. The Big Sert kit for second time repairs is the 5141 kit.

Question - I need to do a second time thread repair on spark plug for a 1987 Harley Davidson Electra Glide Classic, which spark plug thread kit do I use?

Answer - Verify you have an M14 spark plug. If so, then see the 5141 Big Sert kit and the 51407 insert sold separately. The Big Sert accepts the same size spark plug.

Question - Do you have a second time repair kit for an M12x1.25 spark plug?

Answer - No, unfortunately Time Sert does not make a specific kit that's a Big Sert for spark plug thread repair for an M12. The 4212 kit is the first time repair which is not big enough to do repairs when a parts store kit has failed making the hole bigger. Time Sert does have an M12x1.25 larger OD kit made for general repairs which is the Big Sert 5212. It's not specifically made for spark plugs but could possibly work if there's enough material in the head. Also the fact that Harley plugs are washer seat helps the chances of this kit working as well. If it used a taper seat plug I would definitely not even try.

Question - Can a Big Sert kit be used on a Harley Davidson without removing the cylinder head?

Answer - Yes. Time Sert and Big Sert kits are designed to be used while the head is still attached to the cylinders. It's very important to make sure the valves are closed on the side you're working on though. In the picture above, you can see that if the valves were open, the tools used in the repair might come into contact with a valve and potentially cause bending. By ensuring the valves are closed, you not only prevent such damage but also safeguard against any metal debris that may result from drilling and tapping, ensuring it does not get past the valves.

Question - If the parts store spark plug thread repair failed, why would a Big Sert kit hold?

Answer - If a spark plug thread repair from a parts store kit has failed, it can be attributed to the lack of a reliable design or method for securely holding the insert in place. Many kits from parts stores like Napa, AutoZone, O'Reilly, and Discount Auto Parts use a wedge-type tool that requires hammering to expand the top and hold the insert in position. In contrast, With Time Sert and Big Sert thread repair kits design, for the final step, an installation driver that threads into the insert, it cold rolls the threads, and expands the bottom portion of the insert. This method eliminates the need for hammering and provides a more secure and repeatable process. By utilizing the advanced installation driver, the Big Sert kit ensures a reliable and long-lasting repair for the spark plug threads, effectively addressing the issue that might have caused the failure of the parts store kit.

Question - I don't see a drill bit or reamer in the 4412 kit. Why does the Big Sert 5141 kit have a drill bit? 

Answer - The 4412 does not require a hole to be drilled or reamed. The 5141 kit does not use a drill bit but it does use a reamer which makes a cylindrical hole in preparation for accepting threads. See the following article for more details on using a Time Sert or Big Sert kit.

Since 2005, we've been providing our customers with specialty tools and thread repair kits. If you are unsure which thread repair kit is the best fit for your specific application, we encourage you to reach out to us for assistance. By calling our toll-free number at 800-734-8665 or filling out our Contact Form, our team of experts can help you choose the appropriate kit. Our goal is to ensure that you have the tools and support you need to successfully complete your project with ease and confidence. Be sure to book mark us and keep us in mind for your future automotive tool needs.

5th Jun 2023 DennisB

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