number 1: After completing the mission "heavy toll" the bike can be seen behind the abandoned peyote

number 2:the easy method to get it is by entering a cheat code on johnny's phone the cheat code number is:2455550199
number 3:as soon as the cutscene ends on the mission "shifting weight" kill desean before he gets on his bike or when he is on the bike here is a video of it [not made by me]:
number 4:after killing the cheaters on mac's random encounter just like in the mission shifting weight kill desean before he gets on his bike or when he is on the bike
so that's all the tips on how to get it

*if you have the bike save it on Brian's safehouse or Niko's House [seen on video]*
*the bikes can be seen parked or pedestrian's driving it if you are driving the haku bike no matter if you lost it people can still be seen driving it or parked or you can use the cheat code*