oh boy....... only 180 miles....LOl!
Seriously, that is a very ambitious endeavor and a challenge on several levels that have already been mentioned by others here, these are voices of knowledge and a huge amount of experience with the " China Girl"/ "Happy Time" 2 smokers, I do want to add something here that will seem like promotion and that's because it is plain and simple and also what I consider from my experience to be good advice although not the Holy Grail that should be etched in stone by any means...LOL!
OK, personally based on my recent experience, I would highly recommend using a better China Girl engine than what you will find on ebay, Neil aka MotorBicycleRacing & Duane aka Thatsdax both sell kits and engines that are better built and better balanced than what I have had from the the ebay engines, which I currently have 5 of, I also own 3 of the better balanced engines which also have better bearing and the better balanced crankshaft, this makes them a much better engine in my opinion and because the hardest working parts of the engine are higher quality I see no reason why this wont make them hold up better long term in whatever type riding someone does, because of the better balanced crankshaft they are much more comfortable running engines do to much lower felt vibes on the bike frame, do they cost more? YES...! in my opinion are the extra $'s warranted? YES...!
The other parts to consider for better reliability are good quality gaskets that have been sealed with a quality sealer used on the intake gasket especially...., a well tuned carb and everything adjusted properly and all bearing such as wheel bearing lubed with a high grade grease such as Lucas Red Tacky Grease and not just a cheap multi purpose grease which wont stay nearly as well, heavy thorn resistant tubes in the tires which should also be in good shape, lights and reflectors front and rear of bike and a rack to carry extra fuel and one very important thing is at least one rear view mirror on the left hand side of bars so you can easily see at a glance any traffic that may be coming up from behind, people on a cell phone can easily swerve over and hit you from behind if you aren't paying close attention, I see these morons texting and driving and running all over the freaking road all the time from center line all the way to the shoulder, use a mirror and look at it often......
Well, hj630 I know it may seem like myself and other are mentioning many things here to consider, but it isn't at all meant to discourage you at all, we are just simply speaking from experience and want to make sure you understand what you will be getting into on such a long trip with a china girl engine on your bike, its a very doable trip if things are done right and you have a good engine that is set up right and tuned well from the get go, as it was mentioned I also agree that the engine should have a couple hundred (150-200+) of good break in miles on it before a trip like that is attempted, 200 miles of break in and tuning time will let you know how prepared you bike is for the trip and give you time to work out the bugs that (Will) arise with bike or the components of the engine or kit parts, if the install is done right there will be very minimal issues to correct most likely but there is almost always some tweaking here and there that will need to be done to get the build as reliable as it can be, re-jetting the carb is a must on all the engines, they come jetted way rich and it hurts power and performance big time, but it's a very simple process and there are several of us here that can help advise if need be, just read read read, here on the forum, and use the search feature to look for information on any questions you have, there are loads of info that will help you get things done right the first time.
Sorry for the book here, but I'm a bit long winded and just wanted to ring in here and cover everything I could think of and repeat some of the other good advice that has already been spoken here.
Best wishes and a big welcome to our great community, you're in a great place among some great people who really love this hobby and will help you in any way they can to make sure you have a successful build that you can enjoy.