Have no idea what happen there looks to me that you did not chop the bike rather you used the magic wand tool
when you chop it leaves clean lines none I can see on your image
also your tyres are not round hence I doubt you read any of the tutorials
Here
http://www.hdforums.com/m_1950600/tm.htm
Your image of the bike is Poor it looks to be out of focus if you look you will see blue reflections I would say from the road also the seat looks washed out
As you asked for a chop here it is click on link
http://uploadpsd.com/file/26640.psd
for you to make your own sig if you wish!! add your own backgrounds ect.
Not the best for a image as pic was out of focus
Here how the psd turned out just a demo the background is
Have a read of the tutors and have another go it takes time but you will get there
all the best