What is the best case sealer to use on your 2 stroke engine?
I have typed this question into search engines and wasted plenty of hours looking for a definitive answer, but haven’t really found one until… I found this:
“News flash guys: Yamabond (and Hondabond and a few others) are all the same thing! It’s actually Threebond 1127, made by the 3M Corporation. Also happens to be the recommended case sealant for most 2-strokes that don’t use a center case gasket. Like Hylomar, it never really sets up hard, and you’ll only need a light film on both halves, so it doesn’t really squeeze out into the cases. “
So to start with ThreeBond 1127 seems to no longer be available and upon emailing and asking ThreeBond about this not being available and what would be good to use, they gave no answer telling me to go to the dealer or some such thing. Pretty sad when a company can’t even recommend their own product.
2 stroke engine cases are kinda special because if you use the wrong sealant the gasoline will eat it and you will have an air leak and bad things will happen. I don’t like dealers, so I wanted a case sealer that was readily available in an auto parts store or something. So here is a list of more than acceptable sealers to use. I put them in the order of my choice.
I don’t know how long it’s been around, I haven’t really seen it before, so maybe it’s somewhat new? Motoseal by Permatex is my first choice. It says right on the package for “Ideal for case halves” and that it is “Resistant to all automotive fuels”, and there are pictures of snowmobile and dirt bike, which are known for being 2 stroke engines. That makes MotoSeal my first choice.
Next up for me is Hylomar. When I was first introduced to Hylomar I liked it’s blue color, it’s easy to use, it works well with fuel, it cleans off easy and the thing that sold me at the time was that Rolls Royce used it on their jet engines, and if it was good enough for a jet engine and Rolls Royce, it was good enough for me too.
Unlike most sealers, Halomar doesn’t dry or set up. It does have some kind of solvent that evaporates, but the sealer it’s self doesn’t set up like silicone, which dries, but doesn’t harden. If you have two pieces that have been coated with Hylomar and you take them apart, you can put them back together and the Hylomar will still do it’s job. This isn’t a good shop practice, but works well out in the field. Hylomar is also great for coating o rings to make sure they seal. It is harder to find than MotoSeal and more expensive, but is kind of in a class of it’s own due to it’s properties.
Only because I don’t have to go to the dealer the next in line would be ThreeBond 1184. It says it is high performance, OEM specified, resistant to oil, water, high temps, and gasoline. I’m sure it’s a good choice, I just don’t like the company’s attitude when it comes to answering a legit question from a potential customer. I’m insulted. (again…..)
The last two rank the same. They are both good products. They are somewhat available at other places than the dealer these days. I believe too that they have changed the formula to non-hardening, at least in the case of Yamabond. I clearly remember having to scrape off hard dried gray colored Yamabond and what a pain in the ass that was. Other mechanics had complained about the same thing., so it’s not just me. That was years ago though. The whole thing with case sealer is that you don’t want it to harden. maybe that’s why the mysterious 1127 by ThreeBond isn’t around anymore, since it was rumored to be Yamabond and Hondabond. The world may never know because I don’t think ThreeBond would give you an answer.
That sums it up for 2 stroke engine case sealers. These would also be good sealers for 4 stroke engines as they all handle oil. Building Harley engines all the time I normally used a silicone sealer because 4 stroke engines don’t deal with the gasoline, just oil.
DO NOT USE THE FOLLOWING SEALERS ON 2 STROKE ENGINES
Only 4 stroke engines.
As a bonus I will put my two favorite 4 stroke silicone sealers here. The first has been my go to for well over 30 years. Works like a charm when used properly, and your not constantly buying tubes of the stuff every other day. ( I used to build that many engines). You buy a caulking gun and a tube of GE Advanced Silicone. You need to know how to properly use it, you don’t want to just squirt it all over, you don’t want silicone plugging an oil passage. It has great bonding on clean surfaces. It is also very economical as compared to buying small tubes and the caulk gun made it easy to use. It’s silicone, so it handles the oil and heat and water just fine.
Another very good silicone sealant I use is the Permatex Ultra Gray or Ultra Black. These are a heavy duty thick, slow drying silicone gasket makers. The gray and black colors match engine cases too so your job can look a little neater. Slow drying time makes it easier to work with stuff at times too.
These last two I would NEVER use in a million years. Every single job I have seen with either orange or blue silicone is some butchered up piece of shit. As such I have named them “The Orange Silicone of Death” and “The Blue Silicone of Doom.” I would see this stuff just oozing out of gasket surfaces and could only think What the Fuck………..not only that, there would still be oil leaking out of whatever it was smeared all over. Maybe someone, somewhere, has used this stuff properly, but I have yet to meet them.
