Hi there, SmartAlec from NelsonVacuums.com.au
. I have fixed hundreds of Dyson DC07 vacuum cleaners over the last few years and i would say there are 2 possible causes for the loss of suction.
1st is that the filter looks clean but is actually worn anyway. The way to tell is remove the washable filter from your vacuum cleaner. Take out the foam insert this seems to last longer that the other part. Hold up the plastic cage to the light and look at the white part (well it used to be white anyway) you should be able to see light through it. If you cant see through it you need to replace it. Here is a link to that filter for purchase
. To verify this is the problem just run the vacuum without the filter in you should see an improvement - note do not actually **** up material the filter is there for a good reason.
2nd problem is that you have a blockage in your radix assembly. If you take off the whole dirt bin and feel the suction on the upright part where the chamber joins the vacuum (basically bypassing the radix) if there is good suction here you will either need to replace the cyclone top or dismantle and clean it. (it is very difficult to clean as it doesn't completely dissassemble)
Hope this helps - If you want more help send me a message
HAPPY VACUUMING ! :)