Hi Dave, I'll do a search for those rimfire plugs.

I "lost" about a season with my 170cdi as well while on the learning curve of it's funny little quirks and secret upgrades from YS. The pump is my favorite campfire story as I replaced the original pump with the revised unit with the hardened inserts after about 9 months. So far I've spotted 4 different regulator diaphram types with that latest one being a thin white teflon thing. I used a fibre reinforced silicone thermal transfer pad for a TO-3 transistor to get me out of trouble once and it held up well, before I did the right thing and replaced it with an OEM assembly.

Yep, the spark plug gasket took a while to figure out as I was blaming the intake tube o-rings. I still think I haven't got the intake tube in exactly the right spot as it's looking a little "damp" there after a couple of flights when usually the whole motor stays as dry as a bone.

I always lightly face the tappet cover and carb insulator when I pull it down, and nearly always use new o-rings and gaskets when I put it back together. O-ring and gasket kits are cheap enough.