How to make your custom project cafe racer bobber motorcycle a success

Think of a dollar amount and double it             
 It's very important to start with the best possible bike you can afford. I think that ideally the bike needs to be in running condition and mostly complete. I have made the mistake of buying a motorcycle (about 1 and a half motorcycles actually) in pieces only to find that the motor was toast and not worth repairing. I paid $368 for this Suzuki 400 (see pic below) on eBay which was in pieces and with many spares, most of which were worn out or junk, luckily I sold it off in parts and made my money back, and most of  the custom parts could be used on my next project. My current project a Honda 500 runs well and is 90% complete, so I could test ride it, only cost me $750. A motorcycle like any other vehicle is worth more in parts than as a whole. Do a quick search on spare parts prices and you will see this. Even a free motorcycle can cost more to finish than that bike you paid $1000 for. A free motorcycle is such probably because it is junk.

Find a bike that is partially realised

See if you can find a project bike that someone has started that fits your design scheme. There are  many reasons why people sell off unfinished projects. People lose interest, realise they are out of their depth, have a change in circumstances like they need cash or move to a place where there is no area to work . Just take a read on your local online classifieds and you will see all the reasons covered.
Don't get in over your head

 Make sure you choose a project that you can complete with your level of skill. If you have to pay someone or a shop to do most of the work - then it's going to be very costly. A visit to your local custom motorcycle store with a how much will this cost question will give you an idea? Spend hours and hours trawling eBay and forums for ideas and methods to achieve your end result. My vintage supermoto Honda XL500S has only one custom made part on it, but it was not by accident, I did loads and loads of research and spent hours trawling online forums etc for information.
Pick the right style of bike as a starting point

Pick the appropriate motorcycle for your project. Cafe racers are a very popular project idea at the moment and seem like an easy conversion, but a sports bike with a perimeter frame will never look like a cafe racer. I saw on a forum recently that someone had bought a Kawasaki ZZR250 for the conversion to a cafe racer, but even with the right tank etc it just doesn't look right due to its frame being the wrong shape.
Modifying your motorcycle and the law

Which brings me to my next point. Modifying motorcycles can lead to major hassles come inspection time, when trying to get a motorcycle re-registered or if you are stopped by the local constabulary questioning if your mods are street legal. Simple things like lengths of mudguards can be easily fixed, but illegal frame modifications cannot. For example as a rule of thumb, you can modify the frame from behind the rear shock mounts without an engineer's certificate, but any mods forward of that will require one (and they are very expensive to obtain - read many thousands of dollars).
Due dilligence

 When you have found a suitable motorcycle, do your due diligence. Check the frame and engine numbers to be certain it is not stolen, has no finance outstanding on it and is not a write-off. Usually this can be done online or over the phone with your local licensing authority. If you are buying a registered bike, then still check that the frame and engine numbers match those on the registration papers.
Have a suitable work area set aside

 Once you get the motorcycle home, make sure you have a spot where it can be left, preferably under shelter, so you can work on its easy. Take your time and work on it at least a couple of times a week. At first you're as keen as mustard, but after six months and a few setbacks you may be less keen. I like to work on my bikes straight after work for at least half an hour a few times a week. You have also got to consider your neighbours, as they will not like you cutting down your frame at 9pm in the evening! And be patient! Wait for the anti-seize to soak in before a second attempt at removing that stubborn bolt or nut. Just sit for ten minutes admiring your work or visualising what it could be, while the anti-seize does its work.

How I do mock-ups in Photoshop

                Speaking of visualizing, I do all of my mock ups on Photoshop. The important thing is to make sure that all the different parts are to scale. I do an Google image search and find a side view of the motorcycle I will be customising. The larger the image the better, an image that is only 640x480 is not really big enough to show much detail, 1640x1480 is what I would use as a minimum. How do you check everything is to scale? I use the motorcycle's wheel base as the starting point, because you can see it easily. Just measure between the front and rear axle nuts. Do a search for your motorcycle specifications and it will appear, typically it will be around 1500mm. Photoshop has rulers so you can scale it up or down to suit. See the image below for my example. I am using pixels as a unit of measure in the below example and then dividing it by ten. You can see this by the guides I have placed (2 x cyan coloured vertical lines) at about 1400mm.