I need to replace the timer on a series 800 washer

After you advance the knob, you are saying that it will finish the rest of the cycle? If that is the case, more than likely, you will need a new timer for your washer. Hope this helps!

HERE IS A LINK TO YOUTUBE VIDEOS CONCERNING YOUR WASHER..... BUT I DIDNT SEE ANYTHING ABOUT A TIMER. I HAVE REPLACED KENMORE TIMERS....PULL OFF THE KNOB...
REMOVE THE SCREWS THAT HOLD DOWN THE COVER WHERE THE TIMER IS LOCATED.... ONCE YOU HAVE THE COVER OFF..... GET YOUR PHONE OR CAMERA AND TAKE A PICTURE OF WHERE ALL THE DIFFERENT COLORED WIRES ARE LOCATED...SO YOU WONT BE LOST WHEN YOU INSTALL THE NEW TIMER.
https://www.youtube.com/results?search_query=HOW+TO+REMOVE+A+TIMER+Kenmore+Series+70+Washer+Motor+387780

The top or the back does not come of //your post is a little old so if you still need help please ask and I will tell you how to take machine apart......

This assumes that you have a basic Kenmore / Whirlpool top load, direct drive, neutral drain (it doesn't spin until the pump removes most of the water) machine.

First, see the Sears parts site for your washer(s):

http://www.searspartsdirect.com/partsdirect/index.action

Enter the model number (###.######) and you'll see a list of major sub-components with diagrams and parts.

Check the part numbers for both machines in the "Console" section.

Also see the following Whirl[pool Service manual for top load, direct drive washers.

https://secured.whirlpool.com/Service/SrvTechAdm.nsf/2cd44500d572193285256a45004fd9d6/f7e2147fa98b28cf85257122007475cb/$FILE/L-55.pdf

Whirlpool top load, washers use one of two different timers. Depending on the timer the knob comes off differently.

For most, by holding the back of the timer shaft with a thin needle nosed pliers, the knob unscrews.

Appliance parts places don't stock the timers because they hardly ever go bad. Troubleshoot first! .I am not a repair professional. I am a 78 year old man
who has been making his own repairs for about 50 years. So the washer or dryer ID doesn't mean much to me. I came to fixya looking for a schematic for an really old AM/FM radio and found that more than 4,700 people were asking for help with a washer repair. I recently had a washer repair of my own and at that time I found an excellent video which showed me how to take my machine apart. This video made it possible for me to do my own repair. If you are repairing a dryer or a front load washer I suggest you go to www.applianceaid.com where they have very good step by step trouble shooting and repair information on washers and dryers as well as other appliances. If you have a direct drive top load washer and need help taking it apart this video is an early christmas present. I was so impressed with it that when I saw all these people needing help, I wanted to tell them about it. If you look at the back of your washer and the panel is solid (no small inspection plate to remove which would indicate you have a v-belt drive) chances are you have a direct drive and this video is just what you need. You can see it at www.acmehowto.com You will probably still need help in determining what the trouble is and how to fix it. After viewing the video or if you have a v-belt drive rather than a direct drive, I suggest you go to www.applianceaid.com where they have very good
trouble shooting and repair nformation on most
washers and dryers. I think you'll find what you need
there. Don't worry about the timer, they hardly ever
go bad. Good luck with it. If I have helped you, please rate my advice on fixya.

you need to replace the timer

A timer motor advances the timer; if the timer does not advance, you can safely conclude the timer motor is bad, and replace the timer.

Something in the timer came apart. Timer needs replaced. When in good working order, the timer should ONLY ever be turned clockwise..Reversing this could break it.

Your timer has failed to initiate a pause for the transmission to lock in.
Replace your timer. Solve your problem.

Its hard to diagnose these motor problems...takes a volt-ohm meter with a capacitor checker.... and a lot of knowledge if youre up to it, ill try to help.