It is most likelyu that these springs are what is causing your issues. If you can get the EXACT model and serial numbers, you can look up the parts list at http://www.partstree.com/
They can also sell you the parts tyou need.
In addition, you may be able to contact Oscar Wilson (The MTD factory distributor) and they may be able to give you some more information or even a repair manual for this unit.
Their website is: http://www.oscar-wilson.com/ You probably will have to contact them at the phone number listed on the site. It may take a little time to navigate thier phone system, but be patient and you will get the helpt you need.
If you need more information or want to discuss this situation further, you may contact me here at this question anytime...even after you click the "ACCEPT" button.
This is why I mentioned to you that you MUST contact Oscar Wilson by phone.
The website usually does not help very much.
See above answer.