That sucks you dont like the bike my man, I dont understand how the crank arm can fall off, it's a simple component mine came installed & I use the allan key to make sure they are tight from now & then but they never get loose.My bike just needed the pedals installed the crank arms were in place, I believe the pedals are marked L & R maybe you have the pedals installed wrong, maybe the threads are stripped & that happened before you got it. I would call R Martin, they were golden to me with any issues, they will do what it takes. Maybe you should try to return it if you dont like it, not to sound rude but for a 275 lb person this bike may not be a great choice. Most have a weight limit of 220 lbs. But a bigger frame bike like the IZip Zuma, or a Kalkoff may be better. I sold my Prodeco storm @ a loss 2 months after having all sorts of problems & bought this R Martin This after building one before that with a brand new Schwinn MTB & a kit, I do have some experience & can say that my MiPower is over 2k miles now & still impresses me everytime I ride it warts & all, there's no such thing as a perfect bike & theey can be a headach when things go wrong. I dont work or even know RMartin I'm just really into E-Biking & the benifits they give to the economy & your health & wallet & am trying to share some info on a very good value & quality bike for the money. Good luck