I hate to be the bearer of bad news, but as heart-trenching as it may sound to us GD owners and fans, the poor fuel economy of Suzuki GD 110 has left Suzuki guys clueless too. I went to Empress Suzuki today along with the print of picture in this link (fuel consumption record of my Suzuki GD 110). The guy at Suzuki patiently listened to my plea of getting a poor fuel economy according to my calculations, yet Suzuki guys proved a handsome fuel average of 52 km/L weeks earlier.
He honestly accepted that my calculations are indeed right and this method used by Suzuki to calculate fuel average by using a 100 or 200 mL of fuel does not give an accurate value of fuel consumption. He explained, it is so because they do the test on a straight stretch of road at roughly a constant speed and little to no stops at signals. However, in real life we burn fuel in cold starts to warm-up the engine, we stop at signals, we get stuck in traffic, etc. So the 52 km/L was the "ideal" value of fuel average which is impractical in our routine riding scnerio. Also, he said, vertical-head engines (GD 110, CG 125) are notorious for their fuel consumption compared to horizontal-head engines (Spritner, Raider, Pridor, CD 70); however, they give better acceleration (and pick) compared to horizontal-head engines. And yes, GD 110 indeed has a superb pick!
They have raised this issue in their meetings as well, asking company to tell them a fuel-average "slogan" for GD 110 like they have a "73 km/L" for their local line of 110-cc products. I do not know whether it has actually happened or not, but he said they are in contact with Suzuki, Japan to come up with a solution to its low fuel-economy issue. Maybe, only maybe, there would finally be a modification in GD to give a better fuel average.
For now, a 40+ km/L is all you can expect from Suzuki GD 110.