Motorized bicycling needing help

We purchased a bike through u-moto at the end of December 2016. It would seem that we have nothing but problems with this bike. Where we live, the roads are ruff on everything. First it was the gas tank leaking. Now it seems to be that everything electrical is failing. We had gotten a larger, 2 gallon gas tank and put it on a rack on the back of the bike, but my husband had to "trim" the metal rack and it has now broken due to instability. We didn't know where else to go for any kind of advice when it comes to motorized bikes at this point.
Is there anything built in the USA, motor wise?
Where is the best place to buy replacement parts for quality and price?
What kind of rack is suggested to hold a 2 gallon gas tank?

If anyone can answer any of these questions, it would help a ton. We live in southern arizona where it's all dirt roads, really muddy when it rains, and really hard on shocks, so lots of "rattling" for bikes. Thank you in advance to anyone who can help us.

I'm adding a picture of the soldering point that broke due to the roads.

 

Motorized bicycles often end up as unhappy compromises.
A bike simply isn't built to deal with the vibrations, extra weight in unexpected places and a rider sitting as a deadweight in the saddle.
While many people tinker with motorized bikes, actually logging any serious mileage is rare.
Tubus is a brand of rack often favoured by tourers, and should be able to deal with a 2 gal tank.

However, if you are really looking for a reliable, low-cost vehicle, cut your losses and buy a moped.
They are overall stronger and a more comfortable ride, and - unless you insist on pedalling - better for the task.

 

Unfortunately my son does not have a license, otherwise we would go with something else. I appreciate the feedback and will look into that. My husband is thinking of installing some kind of shock absorbers on the back end to help with the vibrations and bumps.

 

oh i hope someone else could help you

 

According to here:http://www.motorizedbicyclehq.com/motorized-bicycle-laws-arizona/
it seems like whether you buy a ready-made moped, or motorize a bicycle by yourself, a license is still required.

Those are unusually strict laws for mopeds, but not much to do about that.

If there's no legal advantage to DIY, and you're doing it for the utility value, I repeat my recommendation to go for a moped instead of a motorized bicycle.

Fitting rear suspension to a Hardtail will take a fairly serious engineering effort. Rear suspension and a rack will be a challenge in itself.

If you feel that you "have" to go that route, you're probably better off picking up a department store full suspension bike to base the build on.

Poor as they are, at least you get the pivots and the basic suspension parts already done.

And being thick-walled steel frames, it's fairly easy to weld in supports and gussets to strengthen the frame, add motor mounts etc.

Or do a search for "motorized bicycle forum", and post there for more knowledgeable responses.