I think this engine is from a small capacity 2 Stroke generator, correct?
BTW, I think its illegal to ride because its not registered, and doesn't have a number plate... Thing is; Any two wheeled vehicle which is motorized by either an internal combustion engine or an electric engine is classified as a "MOTORCYCLE" (Motor + Cycle, okay?) in most jurisdictions including Pakistan... And as such must have proper headlight with low-high beams, indicators, horn & mirrors... You're violating the laws with this bike, brother...
The first step towards becoming a great nation is to follow the rules and laws...
And secondly; a bicycle can't withstand the vibes of an internal combustion engine... It's a dangerous ride, better avoid it for your own safety...
And besides, you can buy a REAL Yamaha YB100 for 12,000 to 15,000 in good condition... Just survey the used bike market...