The stock springs are a progressive rate spring on the tight coils meaning they are not as stiff as the other part of the spring. They do typically collapse under the weight of the machine. Even with very little pre-load. They are also not a very high quality spring and even after 800 miles can sag. That is why there is a huge market for aftermarket springs.
There is soooooooooooooooooooo much info on springs on this forum. Your head will explode! So many brands and opinions. You should be happy no matter what you go with!