Try The Right Stuff by Permatex. It replaces many gaskets on V-8’s and I used it on my Sea King. It also comes in a half size cartridge for a caulking gun.

https://www.permatex.com/products/gaske … ket-maker/

I used it on a 215hp super charged Sea Doo a few years back. They don’t call for gaskets on the exhaust manifold it was suggested to me on a Sea Doo forum instead of what sea doo called for and worked fantastic. I also used it on a 1000 watt Honda generator with inverter to seal the crankcase halves and the valve cover while rebuilding the engine. No gasket is used inside to seal those it calls for another type of sealant but I had it used it and that’s been 3 years ago with no leaks. One thing I really like about it is that it comes out of a spray can like cheese spray just leave a tad hanging out of nozzle so when you go to re-use it for something else just pull that out and its ready to go again. I prefer it now over silicone its way better the name says it all. "The Right Stuff" its pricey but its awesome. Just my humble opinion.
Joe

I am just thinking to myself about this so this is just my opinion so not trying to step on toes.

When I use the Right Stuff and I pull the dried piece out to clear the passage way to spray more out to work on something else the dried piece I pull out is like a solid piece of rubber its very tough to spring when I pinch it between my fingers. It would also work well in an area with vibration it almost might even work like a shock absorber if enough of it was used in an area to dampen vibration. Its some of the best stuff I have ever used. If you ordered the spray type you might spray a tad out and let it dry and see what I am talking about. I really think it will serve you well being used around those bearings and will hold up well.

I don’t know if you should use the Right Stuff on the gasket that goes between the to case halves since you say the old gasket material used is pretty thick to begin with and if you use the right thickness gasket after squeezing the case haves together it would not be needed maybe just some oil on both sides of gasket. It also looks to be a pretty wide gasket.

I am guessing the gasket material should be a certain thickness according to specs and your measurements for the crankcase. Also the cylinder base gasket should be a certain thickness so that the piston clearance from cylinder head at tdc is correct and you get the right compression levels your looking for and piston doesn’t slap the top of cylinder head. When I build 2 stroke sea doo engines I play around with the thickness of the base gaskets to get that right and they sell different size thickness base gaskets but I am guessing you will be making your own and I am guessing the cylinder has a base gasket since I have never worked on one.

It sounds like your making the new brass bushing/bearings for the crankshaft I am guessing that you will make them the same outer dimensions as the old ones or the brass bushings you make slip into a metal retainer and that is where you will be using the Right Stuff sealant around the outer part of them. I am also guessing that if you have the new bushings made and on the crankshaft and you put the crank between the case haves and put them together with no gasket between the case haves and no Right Stuff on bearings that will give you an idea of exactly how thick that gasket should actually be to make shure the bearings also seal between the case halves as well as they can when tightened up. You might even use that plastic squeeze gauge stuff they make to get that measurement of how thick case halves gasket should be when gasket is compressed.

I had heard those engines are hard to get to run right that might be the reason to much slop around the crankshaft bearings against case allowing air to enter the case and thus explains why they put the some kind of rubber around those bearings and used a thick gasket between case halves.

I hope that helps,

Joe

Yes the can looks like cheese whiz. That’s the version I use. I can store it and use it for a couple years or until its all gone. The old gaskets should be close to correct thickness since it was a runner in the past. You might take a toothpick and put just an ever so slight amount of the Right Stuff around the outer edge of the case halves where the clam shell together before you bolt and tighten them up to spec. I would also let the Right Stuff cure for a weeks time to make sure it is cured well before starting engine.

I hope that helps,
Joe

ps that stuff sets up pretty quickly so keep that in mind and work as fast as you can without making mistakes.

Exactly reassemble dry and think about it for a few days. Your a very talented mechanic and will come up with the right solution. That particular motor type sounds like was the end for Thor. They might have put the rubberish stuff around those bearings and then put a thicker case gasket to make up for their less than perfect maching/design while mass producing. Just my humble opinion.

Joe

ps I wonder if that was the motors that Carl had re-worked to sell when he first acquired Thor. I read an article and it sounds like it. It may have been his idea to put the rubberish stuff in there. I can see why you would want that motor.