I stumbled across this chainsaw-based machine in a YouTube video. The label was obscured so I thought it was home-made. I thought wrong.
According to Tony Rumore, who owns one of the XL-100 saws pictured on this page, Homelite introduced it in 1964. It was basically an XL-12 chainsaw motor with the bar swapped out for a baseplate, gear drive, and blade housing.
The XL-12 was introduced the year before and with its magnesium body was the first light-weight chainsaw on the market. At a time when competing models weighed more than 18 pounds, it tipped the scales at a mere 12 pounds. The XL-12 went on to become the most recognizable chainsaw of its day. If you watch the original Texas Chainsaw Massacre (1974) you can see one in action (though not for its intended purpose).
Homelite's circular saw had a much shorter run, and was discontinued it in 1966. The company offered two different models: The XL-100 took an 8 1/2-inch blade and the XL-110 a 10-inch blade. I saw one of the original ads for the Homelite circular saw, which showed it being used on a framing site. I don't know if it ever happened, but I'd like to think some 1960s carpenters used the larger model to gang-cut rafters.
The October 1964 issue of Popular Science contained a fascinating article about the Homelite motor plus the saw, drill, pump, and generator accessories that could be attached to it. Check it out – it contains a cool cut-away diagram of the circular saw.
Gas-powered circular saws are rare, but not so rare that there aren't a bunch of folks who collect, and sometimes – use them. The videos below show the XL-100 in action. Note how the motor exhaust blows dust off to the side; this was a design feature intended to keep dust away from the operator. One of the first things you'll notice from watching these videos is that these saws have variable speed and you can rev the motors. Don't ask me why, but I find that very appealing.
Here's another video of the gas powered circ saw in action. Sorry about the ad at the beginning, but I can't do anything about it because it's not our video. Still, it's worth watching because it's an interesting view of what the tool can do.