I have been searching and researching but am not sure. I have some questions and need some help. Perhaps not using the right terms. Or just overthinking. Is the standard 48cc or 66cc 2 stroke engine mounted at 70 degrees between down tube and seat tube? I have seen 70 and also 75 degrees. Mostly 70. Looking for clean and simple mount. As solid to the frame as possible. I cut out a 70 degree wedge and searched and searched without finding any current bikes to fit the 70 degrees. Did I say I searched. Older frames are definitely recommended over current fair. Over and over. Don’t look to start another long debate on this. But where I live older bikes are not available. Do I need to re-think ebay and look online for older bikes? Or look for other current models. Older frames have smaller down tubes, more in line with engine mounts. Are there any straight tube frames currently sold in 70 degree geometry with the smaller down tube? Should I look for more flexible mounting options? Suggestions? Seen some billet mounts that may work. I want a clean look. I have seen a few frames that have the 70 degree geometry. Mostly older. But are not available to me at the moment. Am sure there are more, but are any available new now? Flying Pigeon Hiawatha Schwinn Motorbike Schwinn Woodlands Royal Enfield I dont want to use a rag mount rear, but cant order anything until I pick a bike. Even thinking about wheel orders would be premature. But looking to lace a few good wheels for safety sake. I like Alex Rims and Weinmann products. Looking at double wall 12 gauge smooth rubber. Any suggestions here would also be most welcome. Going to go with a 48cc 2 stroke. Not looking for a speed demon. Gonna also build one for my wife to ride along. Please help. Love this and this is what I would like to build. Wish I knew the frame. Would extend the seat a bit (I also do upholstery). http://www.bikebound.com/2015/10/18/the-screaming-pigeon-by-dicer-bikes/ Really enjoying the info shared by all the members. Thank you, all of you.