Okay, here's my 2 cents worth of "advice".
I've read through 68 pages of tips & tricks & no one has mentioned this:
1) That cheap plastic insert that shims the carb to the intake manifold? Pretty much worthless and a potential air leak if you don't get the carb seated firmly against the O-ring. Solution? I used a 5/8 heater hose (about 1/2 an inch worth), trimmed it as straight & flat as I could (where it butts against the carb), inserted it into the carb, and then press onto the manifold. Mine was a VERY snug fit, had to dab a bit of grease on the manifold to get it to go in. Once mounted it was very tight and leak free.
2) I live in an area that is INFESTED with sand spurs, a.k.a. goat head stickers. With a normal el-cheapo inner tube you'll get a flat in under a mile. So this is what I did: I got a pair of extra thick Slime brand inner tubes. The package claims it's 5 times thicker than the regular kind. I dunno if that's true, but they also come prefilled with self sealing goo. As if that were not enough, I used the original tubes, cut them down the middle (where the rim is) and used that as a liner between the tire & the Slime tubes. Haven't had a flat since. I got mine at my local bike store, and I've notice Wally-World now carries them too. If they're not available in your area, you can try here: http://www.pricepoint.com/detail/16528-345_SLIST7-3-Parts-74-Tubes/Slime-Super-Thick-Smart-Tube.htm
3) On my aluminum bike, I was a little concerned about the seatpost tube cracking where the motor mounts against it, so I got an extra seat tube, cut the tapered end off (where the seat mount grips it) and sunk it into the bottom of the seatpost tube. Then I added my 1st seat tube on top of it. Had to trim off a little of the bottom to get the seat adjusted for my height, but the added insert helps to reinforce the aluminum frame where the motor clamps onto it, so I feel better about it.
4) If your handlebars vibrates so much that objects in your mirror appear as blurs, this tip is for you: I took a caulk gun and inserted the tip all the way into the ends and squirted enough to create a stoppage. I let it sit overnight and the next day I filled the ends with sand up to a half an inch from the ends. Squirt with more caulk to seal it in and tape it up with masking tape. Flip it over and do the same with the other end. Give it another day to dry. (Might be best for days you're not gonna ride it, such as wintertime or rainy days)
5) Replace all the screws and fasteners that come with the motor with American made Grade 8 hardware. I went with black allen bolts, I think they just plain look better. Go to an auto parts store and get Locktite Threadlock BLUE (not red). Dab just a drop on each bolt and let dry overnight before using on the motor. I've had some of the factory bolts loosen on me and once lost my magneto cover, luckily I was able to find it and reuse it. My motor originally came with phillips head screws on all of the motor, they are made cheap, they strip out too easily, and if the heads are that soft, how much better are the threads? Lowe's Hardware in my town carries the largest selection of all the big box stores so I recommend you shop there 1st. Also, the nyloc nuts are no good after the 2nd time installed/removed, so if you have had to remove them more than once, replace them. Chinagirls vibrate something fierce, and weak nuts will back off on their own.
6) My motor's stock muffler cap came loose on it's maiden voyage and fell off completely before it burnt through the 1st tank of fuel. I suggest a second jam nut over the 1st nut if you intend on running the original exhaust for any length of time.
Hope this helps someone.