So, I tore the 1-40 down last night, and WOW! is it fill of surprises.
First of all, I can finally add a correction to Acres' site that I haven't seen mentioned elsewhere: this saw does not have the 3rd port induction! Oh, it's cast into the block, alright, and there is a hole for it in the reed plate, but the holes in the cylinder wall were never drilled! Furthermore, the transfers only have 2 of three on each side drilled (the farthest two from the exhaust) and the exhaust doesn't have the center hole drilled! It's basically an unfinished block. I bet it's choked down to about half of its capacity. The fuel tank is interesting, too. I was wondering how the fuel/oil mixture was supposed to make it to the bar, and now I know. The tank's cap has no vent! So, as the case heats up from use, it pressurizes the fuel tank, which bleeds mix out behind the bar plate. There is a small nozzle in there that looks like a carb jet which I guess serves to spray it as a vapor and also to act as a calibrated orifice so the whole tank won't dump out through it. That big humped ridge between the carb box and the fuel tank, where logically an oil tank would go? Empty space! Also a PITA as I had to grind a relief in one corner to get the last bolt free to remove the top handle. Another surprise was the stuffer cast into the gas tank. It's big. I'm thinking that with the fuel and exhaust so restrained, McC engineers guessed a small case volume would at least let it rev relatively high, as it's sure not got the flow to make big torque.
Now I'm stumped on what to do with it. It would be relatively easy to drill out the intake and exhaust ports that don't currently exist, as the bosses are cast to guide a drill. The 3rd port would be more difficult, but could be done with a Dremel. It would take some doing to locate them correctly, though -- perhaps just line them up with the intake ports and grind out the barrier so they're all fed by the reed block? I'm also stumped on why they'd use a 2-piece head on an engine that's so critically limited. Makes more sense to me to cast a cheaper single-piece jug if they're not gonna finish the machine work. There are lots of other clues that this thing is unfinished, such as the plugged channel for an oil pump rod, the dummy tank up top, and the oil channel under the bar plate covered by a gasket.
Who was the intended audience for this thing? Surely it wasn't aimed at the pro market; they'd never stand for a de-tuned setup like this. The 33/35/39 family already existed for homeowners, and the 15 came soon after. What were they thinking with this design?
