My personal experience is that there is a time and place for the use of thread locking sealants such as Loctite and commercial grade 2 part epoxies that depend on specific conditions including material and conditions under which it is being used.
With that said I have also found that most people are uneducated on the specific applications and uses of most sealers and grab one willy nilly and end up causing themselves lots of poblems. Sometimes the misuse of products can cause serious damage to the assembly or even injury (or worse) to the user from the adhesives failure.
Some things you should know about thread locking adhesives and metal specific epoxies.
Not all thread locking adhesives are the same. Loctite is made in the USA under very demanding quality control and testing conditions there for you get more uniform results using their products over some of the cheaper brands available through discount sources.
Loctite as well as all other thread locking sealants are age and storage sensitive in that if you have a tube that has been laying in your tool box for over a year you will find that it concentrates from age and has a higher degree of thread locking. If the thread locker has frozen while in storage it should not be used as some of its ingredients can have separated and become ineffective. Likewise if it has been exposed to high temperatures for a long time it can cause a concentration of the ingredients resulting in higher degrees of locking. Most of the time I simply buy a new tube of Loctite for a specific job unless I am sure that what I have on hand is fairly new and not been stored in extremes of temperature.
Using the right formula for the right job and using it properly is essential to proper thread locking and removal of parts after assembly. There are 3 formulas of Loctite brand thread adhesive available to the general consumer:
(from
Loctite website)
- Loctite® Threadlocker Green 290™
Nut and Bolt Locker
Loctite® Threadlocker Green 290™ is designed for the locking and sealing of threaded fasteners. Due to it's low viscosity and capillary action, the product wicks between engaged threads and eliminates the need to disassemble prior to application. Loctite® Threadlocker Green 290™ cures when confined in the absence of air between close fitting metal surfaces. It prevents loosening from shock and vibration and leakage from shock and vibration and protects threads from rust and corrosion. The product can also be used to fill porosity in welds, casting and powder metal parts. Localized heating and hand tools are needed for disassembly.
- Loctite® Threadlocker Blue 242®
Nut and Bolt Locker
Loctite® Threadlocker Blue 242® is designed for the locking and sealing of threaded fasteners which require normal disassembly with standard hand tools. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. Loctite® Threadlocker Blue 242® is particularly suited for applications on less active substrates such as stainless steel and plated surfaces, where disassembly is required for servicing.
- Loctite® Threadlocker Red 271™
Nut and Bolt Locker
Loctite® Threadlocker Red 271™ is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500°F (260°C).
A couple of other things to keep in mind when using thread sealants is that they lose their effectiveness to a varying degree when used on parts that are contaminated with grease, oil or gas. Both surface areas should be thoroughly cleaned with a solvent before being sealed. And the finish adhesion of parts is directly related to the surface area being sealed. That is if you coat a set of surface threads over its entire mating surface the adhesion will be greater.
Personally I have found no use for the Red formula of Loktite on these engines and only use a single drop of the Green formula at the base of cleaned cylinder / head studs in the crankcase and allow it to wick into the threads. And only if I have a problem with front and rear mount studs loosening will I use a single thin line (allowed to dry before installation) around the center of the threads with the Blue formula.
Concerning 2 part epoxies.
There are 3 formulas that come to mind:
First off these are each good products when used in the right application. They are
not thread sealants or thread restoration compounds and while they say solvent / fuel resistant they are not impervious to degradation when exposed to those compounds.
I will not put my (or my friends and customers) safety or investment in jeopardy by using these products to repair threads, or attach parts. There are far better solutions like welding (either tig or
alumi weld) and then redrilling or tapping as needed. I do use JB Weld as a sealer when installing a tapered or threaded pulse port below the jug base or intake not for strength but more to insure there are no air leaks. You can also use these products to repair small cracks and breaks in ferrous and non ferrous metals as long as you remember that it can be affected by heat and fuel and not in a stress critical area.
OK so this is the end of my rant and I hope it is helpful to those new to motorized bicycle riding and small engines, it comes from over 30 years in the small engine industry and seeing people do stupid things and get themselves or others hurt or simply bringing me a machine with 2 inches of JB smeared on it and wanting me to fix it as good as new but "don't worry about the JB Weld fix it works great"... Then I laugh and tell them to find another shop...
*edit* Many years ago I had a commercial customer that had an out of balance diamond blade on a Stihl Concrete saw loosening head bolts and instead of replacing the blade he took every screw out that he could get to and sealed them with the Red formula, I never was able to get that darn saw apart to rebuild it too many bolts either stripped the heads or broke off...