1760 pounds - that's the tensile strength of #35 chain.
How much horse power can it take? That depends on gear ratios, weight of the bike/rider, size of the tires etc.
That being said, I don't think standard #35 chain will break under load from a modded clone engine. If you're really concerned, buy a better quality chain, such as RLV Gold, or go with a 40 or 41 chain instead