One of my lawn darts broke. How can I order a replacement?

No, it is very unlikely that a dartboard should dry out at all. If left in the rain or outside, it might fade and deteriorate, but it won't dry out. In the early 1900's dartboards were made from wood, which did dry out. But modern dartboards are made from fibers that prevent this from happening. Reference:
Where did the Dart Board originate from

With the flywheel key broken you need to remove the engine cover first. This may involve removing the fuel tank as well. There should be a nut on top of the flywheel that needs to be removed. After this is off the keyway is exposed. Replace it and replace the parts in reverse order.

According to Wikipedia "Lawn darts is a lawn game for two players or teams. A lawn dart set usually includes four large darts and two targets. The game play and objective are similar to both horseshoes and darts. The darts are similar to the ancient Roman plumbata. They are typically 12 inches (30 cm) long with a weighted metal or plastic tip on one end and three plastic fins on a rod at the other end. The darts are intended to be tossed underhand toward a horizontal ground target, where the weighted end hits first and sticks into the ground. The target is typically a plastic ring, and landing anywhere within the ring scores a point."

Yes. The law was challenged in the late 1970s but was reinstated in 1987 when a little girl was killed by accident. The injuries have always been very high, 6100 people sent to emergency room due to lawn darts, and therefore they are now banned both in the US and Canada

Similar games to Lawn Darts could be Crown Darts, which is a game in which one uses the same equipment as in Lawn Darts but where the target is a target dart instead of a plastic ring, or Kubb, a similar throwing game that involves wooden batons instead of darts.

Lawn darts are sometimes called yard darts. And for some reason, they can be called Jarts as well.

Lawn darts were outlawed in some countries because they are very dangerous toys. These weighted darts have very sharp spikes that are used to stick in to the ground and have been know to injure people accidentally.

I've purchased my darts through http://www.reddragondarts.comand I'm very pleased with their products and their fast delivery. I stronglyrecommend you to order from them and I also believe that you can find on eBaybut I'll take you some time to find a good one.

The rules of darts are quite basic. I will outline them for you here:

• - Each player turn consists of throwing 3 darts
  
• - Both feet must remain behind the throw line until the dart has been thrown
  
• - Darts that bounce off the board (by hitting the wires) do not score and cannot be re-thrown
  
• - If a dart falls out of the board during your turn, the darts are disqualified and the points do not count
  
• - Darts dropped accidentally can be picked up and still played
  
• - After 3 throws, the player must remove their darts from the board
  

You can get the manual on the links below.

http://orders.sportcraft.com/PDF/78805_78805F_KM.pdf

http://orders.sportcraft.com/PDF/78805_78805KM.pdf