Yeah, I did 24,000 km on a Hysoung GV250 - the cruiser 250, a 2005, the year before they started calling them 'Aquilla'. Top speed I got her to was 132 km/hr, downhill, with a following breeze. Cruised well at 100 km/hr. It did run out of puff if trying to pass on an uphill passing lane and the car being passed sped up to 100 km/hr as they do. But generally passing at 100 km/hr was accomplished by dropping back to get a bit of run up space, then coming on with as much of a rush as possible as the chance of passing arrived - timing was everything.

So your Lifan should be able to cruise at 100 km/hr and peak at something even slightly higher, find another bike shop to check out that speed wobble as you approach 80.