Crank arm problem

[Fisher.King]

I was tinkering with my bike a couple months ago and while I was test riding it, the right crank arm fell off. I put it back fast because I was in a parking lot and got back on my bike, then realized I didn't line up the left and right arms correctly so now one points forward while the other faces up or down, and neither will come off. After looking online the only solution I found was a tool called a 'crank puller'. It is very cheap, thankfully, but now the only problem I have is not knowing which size to get. If someone knows how to find what size I need, or if there is another solution, I would appreciate the help.

I know the nut and cover-cap thing isn't on in this picture, I forgot to replace them before taking it.

[attachment=1456]

[Bill]

Ok don't quote on this but I do believe that the park cwp-7 will be the one you need. Sure there are. Other make types but parktools do last a very long time

[trevgbb]

You say the right side came off? it's usually the left that causes the problems, and this is the one you show in the pic. and this does't appear to have a retaining nut on.
This is a fairly common problem, you should be able to remove this without a special tool except that universal one, the hammer.
Stand on the left of the bike with the crank arm up and rapidly tap the back of the arm, not too hard but quickly and as near to the centre as possible, this will set up a vibration and the arm will usually come off fairly easily, especially as it hasn't been tightened up, you will need a nut to hold it on again and it has to be fitted very tight, or the problem will happen again.
If this doesn't work, I suggest you take it to your LBS, they will do it for you and supply the nut for less than the cost of a tool.
Note that if you ride the bike without the nut and the crank arm becomes loose, you will damage the inside of the locking taper on the arm and need a new arm.