hello im new to this forum, i just purchased a seth thomas with an 89l movement. i looked at all the gears and they seem ok they are clean and not binding in any way. the pendulum swings for about 20secs and than stops. i adjusted the spring slower and faster to no avail. i beleive that this clock needs a 5oz pendulum. thanks for any help

The pendulum won't be a factor, but there are a couple dozen other things that could be,bent hand shaft,bend escape wheel toothe , worn pivots or plates and ------------------or----

I will answer with what has helped me:

First, make a very detailed inspection of each pivot. They must be clean and very shiny. A mirror comes to mind.
There is quite a bit of resistance with a pivot that has some pitting, circular lines and just not shiny. The closer to the end of the time train means the more careful in achieving the required luster needed for the least resistance on the pivot. Teh escape wheel att the end is the most critical of course.
We do not have a fancy pivot polisher but use a simple Dremel with a foot pedal switch to turn it on and off at will (not required but very very handy) with several grades of polishing material, I usually use the red rouge for pivots with a tight cloth wheel made by Dremel also.
It makes a mess so I should do it in an environment that will not matter if it gets a little dirty. Also I use a apron covering most of my chest area. It gets all over your face and glasses. Use Eye protection.
I find that when all the pivots are clean, and all other sources of potential resistance is removed then it will run very nicely. Hope this helps. It is amazing how such a little area can cause so much consternation! Let me know if you have any more questions.

thank you for reply im wondering if the clock not being exactly level if it would create a problem. should i worry about crud in between the mins and hour shafts? this clock was found at a garage sale and had a lot of crud on the out side although the movement is very clean. i sprayed alot of lube on gears thanks once again
regards Manuel

Yes, not being level is a big issue. The beats on the pendulum must be "in beat", but also it could mean that it needs more adjustments done. Try to lift one side or the other to see if you can make the beats to be exactly even.
If you happen to be fortunate enough to have that even beat (in beat) occur when it is perfectly level then you have hit the jackpot.
A note on oil: Please refrain from spraying a movement with any kind of lubricant as usually that will give what a clock what it does NOT need. In fact, WD40 is one of the worst kind of lube one could ever used on a clock movement. It messes it up big time in a short period of time.
If you have a lot of dirt on the exterior, then likely the entire movement will need a complete cleaning. It needs to be disassembled and every pivot cleaned and polished.
Good luck.

thank you once again, im beginning to think its the leveling problem, yesterday i had the thing working fine,for a couple of hours, it was missing one of the little round feet, so i made one and installed it, well the clock stopped working, was the foot removed because of that?, i dont know, the previous owner just had it on the ground during garage sale. when you say pivot is that each shaft that has a gear thru it or the opened "u" item at the top end on pendulum shaft

Sorry I am late in this reply.
Yes, each pivot means where each "shaft" (thru each wheel) rotates in the front and rear plates. The oil will evaporate, collect dust and grime which makes a mess of things and not run freely.
A clock needs no restrictions to make it slow or not run full speed. If it has drag, then it may be that the pivots are worn and not smooth. The pivot should shine like a mirror to keep them from hindering full speed ahead.

Wanye is correct. I should have referenced his post earlier. There are many other factors that can give the movement an excuse to "lie down and go to sleep". Ha.