My 1st bike/trike/moped project ever

I would say brushed , because of the number of the pins in the connector... Brushless had to have more pins to controller (usually five) , because of hall sensors (one for each phase) . Also , seller mentioned that it can serve as windmill generator , which also lead me to brushed version conclusion (I don't see a port for external excitation , which is needed if it isn't brushed motor) . Basically , it's easy enough to find out what type the motor is: if it has removable posts for the brushes, or one side is easily removable (to change brushes when spent) - it is brushed motor. Otherwise - it's a brushless one (it's hard to tell from the picture and there is no description about it , accept mechanical parts and dimensions). Price also tells that it is a brushed one. The only thing that is of any importance - seller wrote that it can endure 24 Amps continuous (torque isn't mentioned anywhere) , so now we know that motor pulls much more (continuously) than your controller is capable to offer (15 Amps at best , they say 30 Amps peak , and the motor probably pulls 50-60 Amps peak).
Before I pile up some more technical data on you , you'll need to explore some more , and get back here with some conclusion (if any) , regarding your setup. However , I'm fairly confident that you'll achieve good performance (well, satisfactory at least) only with different controller and with one more battery in series (48 V system). You can keep the motor (tough - not the best choice) and it doesn't mind overvolting (to 48 V) , as long as you keep continuous current at 24 Amps (peak up to 50 Amps , not more than 30-45 seconds - when starting from a dead stop) , which can be achieved with smart controller (i.e. Kelly). See what Kelly offers in terms of motors and batteries (it is just an example - by no means I'm saying that you need or have to buy any product from Kelly - just use it to compare with others - price wise and technical data included in offers).

Use one gauge thicker wire , just in case...That is , if you have the room for it and it's convenient enough. If Kelly employee recommends that controller - go for it , because I've heard only positive feed back about their customer support... Controller of the choice has 40 Amp continuous rating , which is almost three times of what you have right now Hope that you've told them how much your trike weighs. Good luck with the rest of the build !

It could be simple thing , or it could be gone...Since your controller has protection (it disengaged earlier , when you tried to run it it with other gear ratio) - it could be that protection is stuck in "off" position or something similar ... Multimeter would help , just to see if you have any juice flow trough the bridge or other components in controller. Touching wires under potential isn't a best idea (components in that area of controller aren't that much resilient to shorting). On the other hand , since you have power LED's lit , check the throttle - whether signal is coming out of it (maybe pot in it died). Unfortunately , I'm not an electronics expert , so if you find one - he/she might be of some real help (local radio shack might be a good place to look for one , if you don't know anybody). Definitely , it's worth a try to fix it , because , even if you upgrade (buy different controller) you can sell this one...
BTW - you did great job with jack shafts - looks very professional

Fine looking thing and good job (since I'm carpenter - I must appreciate it ). Tough , I think that you could've saved a few pounds if you used aluminium (aluminum ? ) sheeting for panel/sides construction and wooden veneer with some lacquer (if pursuing "wooden" look) , but never the less - it's looking very cool ...

are you a wood craftsman? that really looks nice. great lines and very professional looking. yes i agree about weight however to me looks are important and that looks phenomenal

Heh , I'm very sorry to bring the bad news , but you've made a mistake...Shellac is natural wood resin and it isn't , by no means, suited for outdoor use or for to much exposure to the sun I've restored in a past real antique furniture (100 , 200 years old and some even older) using all the available technology from the era of certain piece . That included use of glue made of rabbit and other animals bones and use of shellack for finish. Shellack WILL crack on the sun and get pale if water gets to it - that is probably the reason that you can't see real antique furniture exposed to direct sun light , or in use as ordinary furniture (glasses and cups are ALWAYS used with coasters under and that furniture is always and very often polished with carefully selected wax products for maintenance ...). You would be better off with polyurethane coating (UV resistant and water resistant). My advice is to use belt sander to remove shellack (as much as it possible) and than to prepare wood in a way that you imagined (aging wood effect , gold leafs or whatever you've had in mind...) and than to use transparent insulating primer (the stuff that is used when one wants to switch colors of different chemistry) and than to spray few coats of clear PU.
Now , I'm aware that this is waaay off topic , so if You need any help regarding wood working tricks&tips - just send mi message with your e-mail address and I'll be happy to help if I can. As for "I wish I was an artist..." - the only limit is your imagination - all the rest are techniques , since you've already proved that you're capable for creation and good with hands. When you grasp how to do something , you just need practice (I used to make wood carvings to relief myself from stress).

Cool solution ! Once in a while switch battery order in a rack or try to equalize the charge (batteries tend to discharge differently and usually one in the middle get weaker than the others first).

There are no liability issues, if bike is (conversion) designed and assembled properly (using proved components). Of course , there is a matter of including "idiot proof" planning , because potential customers can abuse , or inadequately use certain product (bike) , in a sense : they can run it off road (if the bike isn't intended for that) , or put too much weight on it , or overload it in steep hills , or neglect basic maintenance (proper charging and conditioning of batteries , or miss to tighten the loose nut...) etc... Actually, the only thing that needs very careful approach and thinking ahead is choice of components , especially choice of controllers (manufacturer) and peripheral stuff (throttle , connectors...) - those are most sensitive things on the whole bike and because you'll need to rely on manufacturer's warranty (and speed of response if problem occurs) , because (as I've understood) you aren't much of "electronics guy" ... The rest of needed things is a matter of experience and research (batteries , motors , adapters). My advice is to build at least one more bike and use it as tester for different components and systems (and get more experience while at it), before you start building bikes for other people . You can disregard this , if the potential first customers are nice people and if they will not make a fuss , if something goes wrong and you correct it (presuming that the cause of problem is your fault). I'm very conservative and rigid about making stuff for other people for money - professionally (talking about vehicles) - because I have a lot of experience with that (customers) and I currently make some aftermarket car parts (namely - suspension components), which bring great deal of responsibility (morally , not just lawfully, which isn't much of a concern where I live, comparing to USA). This is only my opinion on the matter , and you'll decide , because you know circumstances in your surroundings better than I. I believe that local bike shop owner has the same concerns about this matter , as I have (though , he could help with his knowledge , as I would do , if I was in his place).
Talking about gas engine - sturdy and heavy frame is all that one needs (mass of the frame helps to damp vibrations and occasional maintenance is needed , like with everything else).
BTW , I also like idea of 48 V system , but wallet has final say in that matter
LiFoPo4 is the way to go (if possible) , and later you can experiment with LiPo's and try to build your own packs , with BMS included. Some people I know use only LiPo batteries (they are skillful with electronics) , because those are cheaper and lighter , but one must know how to handle them , because those can explode in certain conditions..

That thing looks sweet!

Love the wood -

that does look like a fun ride. i bet you are getting excited