replacement parts

There is a post on this site where a guy made his own spring-loaded tensioner out of a coaster brake arm. Also, bike shops (and EBay sellers) sell spring loaded chain tensioners for single speed bicycles that clamp around the chain stay of your frame. That may cut down on how often you have to adjust the tensioner that came with your kit.
Check your chain carefully to see if there are any bulging, stuck or bent links. That could cause the chain to wobble off of perfectly good sprockets. It's easily fixed with a chain tool or a bicycle shop can do it. Good luck.

I have taken some very long rides.

The only "extra parts" I carry is a spark plug, and a spare chain link.

I always carry a extra tube and pump, and plenty of tools to do almost anything on the bike.

I did have a throttle cable break on a 140 mile trip one time. All I did was pull the shielding off and used the remainder cable as a pull string to work the throttle.

I do have a spare CDI and Mag which I got from....http://www.thatsdax.com/....but I have never carried them with me on a ride but if you have them why not?

If you are running the stock chain that came with your kit....it is JUNK! It will stretch and stretch forever. Most of us will replace the stock chain with a good quality #41 chain........http://motorbicycling.com/f3/replace-repair-adjust-chain-1139.html

I've been using my stock tensioner for five years and over 4,000 miles with no problems

There are two ways you need to true your sprocket. I check mine by removing the motor chain so the rear tire can freewheel then brace a pencil against the chain stay and almost touch the sprocket as the wheel is spinning. You can see how much the sprocket wiggles and it will brush against the pencil on the high spots so you know where you need to bring it in with the sprocket bolts. It is hard to get it perfect but keep it under a mm.

As far as being on center, you can check the same way by tracing a line around the outside of the sprocket while the wheel is turning as close to the teeth as possible then if it is off you can easily see where you need to hog it out. You can draw an sixteenth inch line on the side of the center that needs to be moved then grind away with a dremel. I would not mess with it unless the deviation is unmistakeable.

unfortunately, we're all at the mercy of Chinese "quality control" (or lack thereof). a problem i have seen many times, is sprockets are warped. imagine holding a frisbee between your hands...now twist each hand opposite ways. yep. like that.

about the only remedy i have found, is filing/grinding down the outer edges of the teeth. to the point that the sprocket looks like a regular bicycle crank.

sprocket alignment/centering is touchy, sometimes. thew best advice i can give, is just keep messin' until it's right.

as far as CDI and such....just get the least expensive you can find. THEY ARE ALL THE SAME. as with many parts.

parts interchangeability is a cinch.

i carry all the tools/parts just short of an entire motorkit with me, wherever i go. most items have been used at least once, during my travels.

fairracing is correct about stock chain-stretch. its alot.
if you DO get a #41 chain, dont be frightened the first time you fire it up....the wider #41 chain may rub on the casing for a little bit. its harmless. it'll rub itself down and shush.

EDIT:mralaska caught me with me pants down....i was thinking lateral problems, not orbital. sorry.

I've purchased some of my parts from Live Fast Motors . Their clam shell sprocket adapter and spring loaded chain tensioner works great. They ship fast, so if you have a week before the trip, give them a try. As for carrying spare parts, make sure you carry extra cables with you. If the throttle breaks, you're not going anywhere and the reverse for brakes. Even on short trips I carry a bottle or 2 of 2 stroke oil in case. Carrying enough tools to fix anything on the bike is a no brainer. We don't want to see a post saying they had to push their MB back all 100 miles. Good luck!