A Homelite 25-30cc will weigh in at just around 2Kg with a machined flywheel, pitts muffler, carb, and custom mounting setup (which includes a machined 'stuffed' backplate).

A Ryobi 31cc using the same carb and pits muffler, with machined flywheel, will come it a little heavier. Not sure the exact amount other than a friend and I both did our conversions at the same time and his scales showed the Homelite to be lighter.

Having said that, the Ryobi has a smaller crankcase and is much easier to convert.

Powerwise (25H vs 31R), both will be similar with a WA-167 carb. If you go for the 30cc Homelite the peak RPM is lower, which I attributed to radically revised exhaust port timing (compared to the 25cc). Of course, different markets apparently get different porting (going by my web-research).

If weigh savings are a major criteria, it's best to buy one of the small Chinese gasser engines. They will weigh roughly half a Kg less and come with electronic ignition and much more power (relatively speaking).