Project Scooter Cannonball 2020

Maybe no interest on the site for this, but there is a transcontinental cannonball that's run every two years here in the States. The event takes place over ten days, and along the lines of a rally somewhat, with a number of checkpoints daily. Part of the rules require it be done on a single cylinder scooter of less than 280cc. Since first reading about it a few years ago, I decided to try to add this to my bucket list. I figured I'd like to do it(iF I do it) on my own modified machine. To this end, I picked up a cheap Yamaha Majesty 400 scooter, with no body plastics whatsoever. The engine is the same, physically, as what is in my Yamaha Morphous 250. Since I have to pull the Morph apart(bad bearings and/or crank, I'll replace the 250 and put the 400 into the Morphous. Finally, I'll be able to start on my Cannonballer. I like these engines because they are four valve heads, and usually very dependable. (I broke mine by doing too many W.O.T. runs for too long). Preliminary plans call for a lowered and modified seating position, a dustbin styled fairing for the front, an auxiliary fuel tank(s) and some sort of enclosure in the rear. The 250 in stock form averages about 62-65 mpg U.S., the stock tank is 3.7 gallons, and can run at a steady speed 65-68mph safely. I think I need to increase my range to about 325-350 miles and would like to be able to run 70-75 steadily. The event is timed for each stage, so If I can avoid refueling, that will save me quite a bit of time. I'm hoping the dustbin will help to raise the cruise speed as well as improve the fuel mileage slightly.
What do you guys think? Am I just a dreamer with unrealistic expectations? I'm looking for any and all suggestions-Thanks

 

^ That looks like fun! Here's what I'm starting with, along with the broken 250,

http://loversofmoto.com/wp-content/uploads/parser/Yamaha-Majesty-400-Majesty-400-4.jpg

pretty much a blank canvas. Wheels are 14" front, 13" rear. I'm trying to see if the 15"/!4" from the TMax will work without too much modification. Any help/ideas from AUS would be greatly appreciated!

 

I chose this chassis because it's fairly light(cast aluminium) and relatively strong-plus I got it dirt cheap. I followed Vetters build, but boy, with those huge tails, those things are ugly and I would think not very practical for everyday riding. I will need some sort of enclosure in the back, though, and will have to fab up a set of handlebars to match the lower seating position. I'm not too worried about sidewinds because I'll have to have pretty good sized cutouts on the sides to accommodate the reclined feet first seating position and around the bars. I'm not needing to maximize streamlining, but anything I can do to get a boost in fuel mileage and a bit of a bump in power and speed. Something similar to this:
I appreciate the thoughts and comments so far, it will help keep me on task! Being that it's scooter based, I'll be playing with the variator and rollers, and clutch springs. Having a similar bike as my daily rider will help me testing different combinations. I'm also following Ruckusmans project and looking for things I can apply to mine. I'm big on plans, but short on dollars.

 

All road rules apply and sometimes cities can't be avoided. Speeding isn't officially encouraged but.... On my road going Majesty, I frequently run 180-190 miles(290-305)km and only stop because I have to get gas. I've done many unofficial Ironbutt runs-1000miles-(1610KMs)<24hrs, so I'm used to long hours in the saddle.Because the competition is spread out over ten days, the longest run should only be 325-350 miles(323-563kms). While I think I need to stay relatively stock,power wise, for dependability, I will need to boost the power to be able to cruise @ 70-75mph for long periods, and get close to 70mpgs. While that may be easily achievable on a bike, it's a lot tougher on a 250(or so) scooter. I really appreciate all the comments and ideas I'm getting. There sure is a lot of knowledge on this board!

 

Using a link provided on this site, I see I may be able to sleeve my cylinder to get pretty close to the maximum displacement allowed. You guys rock!!! My 250 engine shares almost everything with the 400 motor, the only differences I can see is in the bores-66mm vs,. 83mm, having the same stroke of 73mm, and the intake and exhaust ports being slightly larger in the 400 head-both which are 4valve heads. Information for these engines are severely lacking, so I guess I'm in for a lot of trial and error. Although it bites having to deal with ta variator instead of gears, I became aware of a 250/300 Yamaha Versity scooter(not available here) that has a 14" rear tire that may fit, that might help with effective gearing.

 

Thanks. I did some measuring and found a couple of 13" car tires that will fit that are 1 to 1.5 inch(38mm) taller which will fit. Since I've been running a car tire on the back of my roadgoing scooter and bike, for a few years, I'm used to them. That should help raising the cruising speed if I can get the grunt out of the engine to pull them. I didn't think there would be much interest in a scooter thread, but you guys are awesome!

 

I'm getting closer to getting some real time to spend on this project. Instead of boring the 250, I've picked up a 400 engine that's mostly apart. I've located a shop that will sleeve the 400 to get me too 279 cc-just under the maximum allowed. My thinking is that de-boring the 400 will provide a little better dependability than pushing the 250, and the 400 head breathes slightly better. I 'm now checking to see if a Tmax, either the 500 or 530, piston will fit and the pin size is compatible.

 

I think I just sold one( I have two) of my road going Majesty400s, so that should free up some cash to finally get started on my frankenmotor. Thanks to a post on this site, I've located a source for my sleeve, with the proper O.D. and I.D. As soon as I locate a piston and pin with the right dimensions, it's off to the machine shop with the block. I'm thinking just some minor port clean up and a good valve job should suffice for the headwork. The D.O.H.C.s are in great shape and slightly better than the 250s, so they will get reused. I'm hunting for a good aftermarket timing chain tensioner-if there is such a beast available-because that's what caused the original failure.
It's good to finally begin to start making some progress.