Officially, riding along the tracks is prohibited. As exciting as it sounds, getting past the cops at the bottom would likely turn in to a reception by the cops at the top of the tracks. Once at the top there is no where to make a quick get away.

There must be a road to Aguas Calientes, as there are dozens of buses ferrying tourists up and down the mountain to Machu Picchu. Did they bring the buses in by train? I suspect there are some really bad roads, which are closed to private traffic.

Step by Step and the gory details
 

Step by step:

1. From Cusco take Peru 28 to 28B, the "sure to be open" route, a 100% paved road. This route adds 20 kilometers to the trip and certainty of good roads. Total mileage to Santa Teresa 231 kilometers.
2. Otherwise take Peru 3S west out of Cusco. Memory tells me I tried the road to Huarocomdo which was undergoing construction (March 2013) with closure to north bound traffic until afternoon. I back tracked to 3S and took the road to Chinchero. This route is not completely paved, but fairly good surface.
3. Once on 28B point yourself to Ollantaytambo. Get gas here. Maybe 30 minutes out of town you will start climbing a mountain range. Be prepared for mountain temperatures.
4. Very near the center of Santa Maria there is an unmarked left turn that leads to a bridge and the road to Santa Teresa.
5. Follow the road southeast out of Santa Teresa to the hydroelectric plant. (~20 minutes.)
6. Stop at the green corrugated metal booth and register before starting up the trail to Machu Picchu. The officials will give you directions to where you can store your motorcycle at the hydroelectric plant.
7. From this point you can walk along the train tracks or take the morning train to Aguas Calientes and an early afternoon return train. It is prohibited to ride a motorcycle along the train tracks.
8. Once you reach Aguas Calientes, find the ticket booth and pay the entrance fee to access Machu Picchu. Buy in advance during high season.
9. Locate the bus station, purchase a ticket to the top, then wait for the next bus. The buses depart about every 15 minutes, or less.

Google Map – the paved road route
http://goo.gl/maps/jIiQS

General food and lodging advice, and more:
Aguas Calientes travel guide - Wikitravel

Note: There are ATM machines in Aguas Calientes

MY RIDE TO MACCU PICCU

If you don’t have much time and have the funds, take the bus, train, bus combo to Machu Picchu. Riding a motorcycle, then hiking from the hydroelectric plant takes more time and energy. You might save a little money, but in the big picture, not that much. On the other hand, it’s an adventure to “ride” to Machu Picchu and you’ll have serious bragging rights.

Google Maps reports a distance of 209 miles from Cusco to Santa Teresa. I thought I could get Machu Picchu and return to Cusco in the same day. What was I thinking? I knew from experience that you need to double the time Google provides for routes in Latin America, but for some reason -- reason flew out of my head and I thought it would take less time.

Departing around 9:30 AM, I lost time trying to escaping Cusco due to typical GPS misguidance. West of Cusco, taking the GPS "direct route" after leaving the highway I encountered construction, then a road closure. There was the option of waiting a few hours for the road to open, but I didn't feature that. I tried taking a secondary road, but the mud was too deep and the road too steep for my comfort, so after a few miles I back tracked and found an alternate route. I wish I could be certain about the route I attempted and the one I ultimately took, but my GPS went missing along walking along the train tracks to Machu Picchu and the traces were lost.

Depending on your choice of route to escape Cusco, the next way point is Ollantaytambo. This is the last regular gas station. I failed to buy gas here and bought more expensive fuel east of Santa Maria from a primitive gas station. It was a place where I estimated the amount I needed, paid in advance, then the owner brought out a large container of gas. The road from Ollantaytambo to Santa Maria goes over a mountain, with dozens and dozens of switch backs. The views are incredible. The switch backs make the trip much longer than you might assume based on distance. Be careful going around the switch backs as oncoming trucks often cross the middle of the road into your lane. Approach each turn with caution and be prepared to get out of the way of oncoming traffic. Motorcycles are not given little respect from trucks on these hairpin turns.

As I descended the mountains between Ollantaytambo and Santa Maria I dropped the motorcycle in one of the water run off streams that cross the highway, the bike landing right side down in a foot of water. A few months earlier a friend dropped his motorcycle in water when returning from Machu Picchu. His bike was submerged for 5 minutes. It took a month to get parts sent to Cusco. Driven by fear that I would suffer a similar fate, I picked up the bike faster than I have in my life. Water flooded one pannier, soaking a few paper items and filled my boots. After recovering, I pressed on to Santa Maria, slightly shaken and wet. If there is rain, expect to make several water crossings. Some are shallow and others are quite deep.

Near the center of Santa Maria there is an unmarked road (left turn) leading to Santa Teresia. A combination of GPS and asking for directions got me over the river, and headed up the mountains to Santa Teresa. It took me an hour or more to get from Santa Maria to Santa Teresa. The route is not for the faint of heart, many steep drop offs along the road and of course no guard rail. (Ha!) I felt this road was more "challenging" than the Death Road in Bolivia. That road has a world famous reputation due the volume of traffic and number of fatal accidents. The volume of traffic and number of accidents on the Death Road has decreased following the construction of a parallel modern highway, but I digress. On the road to Santa Teresa there are several water crossing. At least two are deep and should be studied before executing a crossing.

Arriving in Sata Teresa around 6:00 PM. After investigating and failing to find a cheap room with parking, I checked into the most modern hotel on the north end of town. I was quoted a reasonable rate and stored the motorcycle into the lobby. The next morning I was presented with a different rate, more than double what was agreed to the night before. The management showed a receipt book to prove the validity of the higher rate. They failed to point out that many of the receipts for occupancy of two or more people. I held my ground, but for lack of exact change paid slightly more than agreed to the night before. I have learned not to wait for agreement, but to pay what I know to be the right amount and leave. It was a matter of principle, paying something close to the local rate, and not giving in to being bullied and scammed. Often I have paid for my lodging the night before to avoid "confusion", and ensuing "extra charges", which can include parking fees...even when parking was said to be included on check in.

My boots were soaked which would make the planned walk along the train tracks from the hydroelectric plant to Aguas Calientes rough on my feet. I have very wide feet and mail order my foot wear, so the prospects of finding something to wear in a small Peruvian mountain village were dim. To my amazement I found a pair of cheap rubber sandals in a shop that fit my extra wide feet. The sandals were a touch snug, but they would work.

The next morning I left for the hydroelectric plant...and went the wrong way leaving town. Lost an hour and saw a small village before back tracking and getting on the right road to the hydroelectric plant. There is a small green building where hikers register. They will give you directions to the guy who will store your bike. The storage shack (yes, they guy lives there, very friendly) is across a bridge and down the road a short distance. You can store for the day or overnight.

Given my foot wear issues, I would have preferred at this point to have taken the train from the station near the hydroelectric plant to Aguas Calientes, but missed the train due to the time lost taking the wrong road leaving Santa Teresa. It’s an 11 kilometer walk to Aguas Calientes, ~2 hours depending on your hiking speed. There are signs along the way that reveal the number of kilometers to Aguas Calientes. There are also signs that say you must stay off of the railroad tracks. There is usually a foot path running alongside and I rarely found a need to walk on the tracks. Take water and a snack. There is a small restaurant about halfway, but I had my own supplies and can't comment on the food. Stopping at an open air shelter near a hotel/ restaurant halfway is where I think I lost my GPS...

Arriving in Aguas Calientes locate the ticket center for Machu Picchu. Entrance is limited to something like 3500 people per day. I rolled the dice and got lucky, securing a ticket for the same day. I didn't buy my ticket in Cusco and was in the last few hundred of tickets sold that day. I think you avoid travel agent surcharges by buying the ticket from the official office in Aguas Calientes. It is not clear to me if you can buy an entrance ticket in Cusco from the tourist board. Check for info at the Peru tourist office in the Plaza de Arms (northeast corner of the plaza.) Most of the people I met bought tickets through an agency and probably paid more.
Next stop, buy a bus ticket that will get you up the mountain to Machu Picchu. If you have the time and energy, then walk up. Remember you are at a high elevation, so it will not be an easy walk, the road is narrow and there is serious bus traffic. Food is expensive at the top of the mountain. Think stadium prices. There is a restaurant and a snack stand. Everything was overpriced and I wasn't hungry, so I skipped eating and took in the site.

I got lucky again as the site was not shrouded by clouds. Got the classic picture of the site when first arriving, with and without yours truly, I took a fairly quick walk around the site. Given more time I might have hired a guide, but wasn't in the mood. It is crazy, but I was eager to get back to Aguas Calientes and hopefully catch the train back to the hydroelectric plant to avoid walking back 11 kilometers. The clouds rolled in and light rain began. When I got back to the bus loading area there were long lines. By the time I got back down the mountain and found the train station I had missed the only afternoon train to the hydroelectric plant. Ok, I'm walking back.

I noticed people tent camping large groups below the tracks as I got near Aguas Calientes. If you are inclined consider camping. There is plenty lodging in Aguas Calientes, but I didn't look into the prices as I was heading back to Cusco where I had left the balance of my luggage. I had thought I could reach Machu Picchu and return to Cusco in one day, so I hadn't checked out of my room. Getting back to Cusco that night was my goal.

The walk down the train tracks to the hydroelectric plant took me a little over 2 hours. I was stopping to wash small stone out of my sandals along the way to prevent blister and chaffing on my feet.

It wasn't until I was back at the hydroelectric plant that I realized my GPS was missing. Damn, no turning back as I wasn't sure where I lost it and if it could be found (not likely.) As I passed the hotel in Santa Teresa I mentally gave them the finger and rode on. The water crossings coming back were roughly the same level as when I went up. These crossing are tricky as you are basically crossing a raw stream with rocks of various size. Study the stream for rock and current, then pull back to get some speed, put the engine in first gear, face shield down, stand on your pegs and don't stop whatever you do. If you drop the bike, kill the engine, then pick it up as quickly as possible. Pick you bike out of water like your life depends on it…

Arrived in Santa Maria around 7:00 PM, took a short break then headed east toward Cusco. I made it back to Cusco that night, now without a GPS, arrrgh. Instead of attempting the secondary roads directly west of Cusco without a GPS, I rode further east on 28B, which goes north and slightly over shoots Cusco to the east before dropping down on 28. It was a long, cold ride back in the dark, through drizzle, back over the mountains. It was St. Patrick's Day and I was determined to the Wild Rover Hostel, an Irish hostel and bar, for a wee bit of the party. Near midnight I got to Wild Rover, returned a rubber Guinness football that I had borrowed to use as a photo prop, and had a quick beer. Being exhausted from the cold and rain I packed it in near midnight.

Visit my blog for the hydroelectric train schedule and a few photos: Peter's Ride: Macchu Picchu

Damn. You left Cuzco mid-morning, rode and walked to M.P., then rode and walked back to Cuzco on the same day? And I thought the OP was in too much of a hurry..... That's crazy.

I've been mulling over the question of how the buses got there. I idly assumed they came in by train and never bothered ask the locals. But looking at the terrain, I can't think where any hidden road could be.

You're probably right about booking yourself a reception party of cops in Aguas Cal if you tried the railway on the moto, but there is a bit of me that thinks the Peruvian cops may admire the achievement and only ask for a reduced bride....

The way I read it, he spent two days doing that. Still not easy. I took the train from Ollantytambo.

Yup, you're right. I've gotta work on my reading comprehension. Blame it on faulty schooling and inadequate parents!

I drove my 4x4 into Santa Teresa 3 years ago during rain season (Jan-feb) and also at the time of an El Nino effect. The road from Ollantytambo to Santa Maria was under construction, but because of the weather, in many places large portions of the road had fallen into the valley. The road from Santa Maria to Santa Teresa was near impossible to drive with avalanches of rocks everywhere. Many people died on the roads there during the 3 days i did the drive in...so for everyone thinking of doing this drive, please be careful.

The road to Santa Maria is a beauty now - great tarmac and switchbacks all the way. The dirt road to Hydroelectrica is fine in the dry season, but I suspect it would be a bit sporty in the rainy season.

If your planning this trip, don't forget there are great hot springs at St T. Give yourself an extra day and chill out there.

Two days...too fast
 

With getting lost leaving, construction dead ends, trying then back tracking a seriously muddy track, it took me a day to get to Santa Teresa where I spent the night. The next day I reached Macchu Picchu, after a smallish detour, and made it back to Cusco that night.

I break too many rules of quality travel. The primary one is to travel slow. I fell victim to a schedule. At that point I was counting the days left to arrive in Cartagena where we would sail to Jamaica, Cuba and finally Mexico. At this point I was seven months into the trip, getting road weary and a bit burned out on South America. It happens. The trip ended up being 9 months and covered a lot of ground, with hot spots of intensity and long riding stretches connecting them. A "South American Sampler." No regrets, no excesses. I rode my ride.

Next time I embark on an overland adventure, my wife will come with me and there will be no return date. Maybe no return, per se. I dream of selling the house, contents, cars and the rests of the junk that seems important to us now. Fill a 40 foot container (or smaller) with the essentials and store it somewhere, sending for it when we have found our own little piece of paradise. You start with a dream, frame it out, collect the details, then start checking thing off. If things go well, the above could happen within the next ten years.

Getting back on topic, Macchu Picchu is amazing. Just go there, one way or another.