Hi,
An engine needs air, fuel, and spark to run. If you have a nice blue spark at the plug then next check for fuel, if you have fuel getting through, make sure you have air.
If the plug is dry after trying to start the engine you are not getting fuel and should diagnose from there (filter, fuel valve etc). If you make sure all the pipes, connections, hoses and clamps are tight, you should get air (don't forget a vaccum is needed to open the fuel valve).
Don't just buy random components to fix a snag, it gets expensive.
Cheers
westcountry
December 2013