I have two 8 year old Eureka lemons growing in pots. I repoted them 2 years ago thinking they were root bound. They were not and they have never been the same. They almost died the first year because the soil mix was not the same and I did not get the watering correct. (that is solved) but it appears that they have lost their Eureka lemon genes. They do not produce fruit, only thorny branches. The branches are all above the graft.
1. Should I take them outside and run them over with a big truck.
2. Hold my breath and maybe fruit will start growing.

I assume this is what I get for not staying current with this forum (it has been 3 years since I last read anything). I hope to correct my past sins. http://imageshack.us/g/233/10005400001.jpg/ The lemon bud are only one branch on a plant all others have different leaves. PS: The flowers are from a Coleus.

A photo would help diagnose your problem

It's very hard to tell, but in this photo it looks like the graft is up near the yellow tag...

It looks that your tree is infected with scales! http://imageshack.us/photo/my-images/577/10005440001.jpg/

Yeah it does look like scale and I agree, the graft is by the yellow tag, so those other branches are rootstock and draining life out of your lemon.

Where did this myth come from that growth from rootstock is bad for the graft? Check this Calamondin grafted on meyer:

Does it seem unhappy?

Now that's cool. Obviously the lemon was a rooted cutting from mature wood.

that is awesome!

This is the spot Laaz was looking at and it looks like the rootstock was cut here, but a picture from another angle or two would confirm it.

i completely agree with mark stating that the rootstock growth (sucker) drains a lot of energy which could be put to better use, in this case scion growth.
if you left both, sucker along with the scion, after a while sucker would take over the scion. a sucker growth is much more vigorous than scion, in most of the cases.
here's another beauty (sour orange). however this is something you usually don't want to happen. otherwise you wouldn't graft.
yet another rooted cutting (sour orange) used as rootstock.



take care,
igor

After Laaz post about the graft I looked at that spot and it could be where the graft is. I trimmed the suckers off the tree in the picture. There still is 2 lemon branches still producing fruit. My other tree which is the same age has only suckers. The main stock is dead. So I took my first suggestion and took three of my none producing trees and ran them over with and big truck and backed up and ran them over again. I will post new pictures in a day or so. All this advice is very helpful. I will make another post - How to wrap christmas lights around the pot. I tried it and did not see much of a temperature increase. The pots never get below upper 50's low 60's at night. I guess I did not wrap enough strands around the pot.