Judging condition of top end?

I know...
But the local Stihl shop recommended it to me anyway for the clamshell type motors... They could be crazy though...
It's not out of the realm of possibility...
Though over the years, I've never had a failure...
Just lucky??

 

Oh well, I've got a tube of the Ultimate stuff on order from a local auto parts shop. I'll post back here when I get the things together.

 

I got a tube of the Permatex "Motoseal 1 Ultimate Gray" from an old-school auto parts place a few miles from home. It was only $7 for the tube, and was easy to work with aside from being a bit challenging to apply in small amounts in recessed places because it doesn't come with a long, pointed nozzle. The instructions say to apply a thin layer to both mating surfaces with a small brush (I used an acid brush) and then wait a minute before assembly. The 1-minute wait isn't drying time, but rather seems to allow brush strokes to flow out so you get a nice, even film.

The instructions also say it seals in 20 minutes, so I went ahead and installed the rest of the top end and attempted a pressure test about 45 minutes after assembly. It immediately blew out towards the right rear, behind the sprocket-side bearing and exactly where it was leaking before I took it all apart. So, I took it apart again, and found thicker sealant in the area of the leak, indicating that that area hadn't been pulled together tightly despite my having torqued all the screws. I cleaned up the parts and after some experimentation found that the screw in that corner was bottoming out in its bore before it could pull the parts together. I used a little scraper to knock some debris out of the bore (mostly old sealant and maybe a shaving or two of aluminum), and that made just enough clearance for the parts to go together the way they should. I put it all together with new sealant, and anticipated being able to build the saw up and give it a test run today.

This morning's pressure and vac tests went a lot better than before, but I found some slow seepage where the manifold is clamped onto the cylinder inlet. There's no hose clamp on this thing and nowhere to put one, just a plastic snap-together plastic clamp that's integral to a multifunctional part called the "manifold partition." I cut a strip of a soda can for a shim and slipped it in-between the clamp and the rubber manifold to tighten the grip a bit. That took care of that little leak, but I was still getting some seepage elsewhere. I slopped around some soapy water and started getting bubbles (pressure test) from in-between the rubber manifold and that manifold partition. I pulled those parts off again and separated them for inspection. They looked okay, aside from some sawdust that had worked into the crevices. I began wiping them clean, and a little plastic nipple that is part of the impulse passageways fell off in my hand.

So, another part to order and no test run today. Soon, though. There's no stopping it now.

 

Victory!