Problem with the RPMs

Usually when the mixer runs only on high speed it is caused by the control plate adjusted incorrectly or the control plate spring unhooked. Remove the trim & end cover on the mixer and check the control plate spring, if unhooked, attach to bottom of the control plate and squeeze the spring end, also check the speed control plate screws,there are 3 screws on this plate, one at the bottom two at the top, see if adjusting the top screws slows your mixer down.
Next check the wiring of the mixer, Insure everything is wired correctly, to get wiring diagram go to the last page of the service manual. Here is a link to the service manual: http://lib.store.yahoo.net/lib/mendingshed/kitchenaidservicemanual.pdf
If neither of those fixes the problem it is probably a bad phase control board, or a shorted phase control board. With the line cord disconnected, pull the t-bar contacts to open and insert a piece of paper between them so they cannot close. Reapply power-the mixer should just run or buzz trying to run, if it operates at full speed the phase control is defective and needs to be replaced.
Use the service manual to aid you in taking apart the mixer, trouble shooting the problem and putting the mixer back together, based on the mixer only running at high speed some of the time I would assume it is the speed control phase board.
If you have any questions let me know.
Thank you,
Colleen
Customer Service
MendingShed.com

Make sure your Beater can slip in and out of the Beater Shaft
easily. Do not force the beater onto the Shaft if the shaft is bent.
If it cannot be removed easily by hand, use a soft rubber mallet
(not a steel hammer) to slightly tap the beater so it can be moved
up and down the shaft or from side to side. Then you can easily
turn the beater left and remove it from the shaft.

From Kitchenaid Manual:
To Attach Flat Beater, Wire Whip, or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Slip beater onto beater shaft and press upward
as far as possible.
5. Turn beater to right, hooking beater over pin on shaft.
6. Plug into a grounded 3 prong outlet.

To Remove Flat Beater, Wire Whip or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Press beater upward as far as possible and turn left.
5. Pull beater from beater shaft

Make sure your Beater can slip in and out of the Beater Shaft

easily. Do not force the beater onto the Shaft if the shaft is bent.

If it cannot be removed easily by hand, use a soft rubber mallet

(not a steel hammer) to slightly tap the beater so it can be moved

up and down the shaft or from side to side. Then you can easily

turn the beater left and remove it from the shaft.

From Kitchenaid Manual:

To Attach Flat Beater, Wire Whip, or Dough Hook

1. Turn speed control to OFF.

2. Unplug stand mixer or disconnect power.

3. Tilt motor head back.

4. Slip beater onto beater shaft and press upward

as far as possible.

5. Turn beater to right, hooking beater over pin on shaft.

6. Plug into a grounded 3 prong outlet.

To Remove Flat Beater, Wire Whip or Dough Hook

1. Turn speed control to OFF.

2. Unplug stand mixer or disconnect power.

3. Tilt motor head back.

4. Press beater upward as far as possible and turn left.
5. Pull beater from beater shaft.

Make sure your Beater can slip in and out of the Beater Shaft
easily. Do not force the beater onto the Shaft if the shaft is bent.
If it cannot be removed easily by hand, use a soft rubber mallet
(not a steel hammer) to slightly tap the beater so it can be moved
up and down the shaft or from side to side. Then you can easily
turn the beater left and remove it from the shaft.

From Kitchenaid Manual:
To Attach Flat Beater, Wire Whip, or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Slip beater onto beater shaft and press upward
as far as possible.
5. Turn beater to right, hooking beater over pin on shaft.
6. Plug into a grounded 3 prong outlet.

To Remove Flat Beater, Wire Whip or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Press beater upward as far as possible and turn left.
5. Pull beater from beater shaft

The Hobart H600 is a 2 horse power, 60 quart mixer, it can be used for many things in the kitchen. It can be used to make about any kind of food that needs mixed, wiped or kneaded. It works well in a pizzeria for all facets of making pizza from the dough, to shredding the cheese with an attachment, to a restaurant that makes mashed potatoes and fresh bread, to a full service bakery.
However, the biggest thing that you need to know is the capacity of the machine. As overloading the machine can cause damage that may be costly and take a technician to fix. I do not know what attachments you currently have so I will go over a few of them.

The main attachments are a Wire whip, Flat beater, and Dough hook. There are three different types a "D" wire whip (has many wires and is evenly spaced) this is used to whip egg whites, whipping whip cream, etc. The "C Wing" (has six tines in it) is used for items that are heavy for the D wire whip, like whipping potatoes or icing. The last is the "I" whip is similar to the D wire whip just with less tines. The flat beater is used to mashing or mixing examples are mashed potatoes before they are whipped, cake mixes that do not require whipping, batters and icing. The Dough hook is used for kneading dough examples are pizza dough, bread dough, etc.

The biggest thing when using your mixer is to know its capacity for the material that you are mixing. All though this is one of the bigger machines it still has limits. You should refer to this the following link for the capacity of your machine: https://my.hobartcorp.com/resourcecenter/ProductDocumentation/F-7701.pdf

There are also a few attachments that can be put on to the No. 12 attachment hub. A few of these are a vegetable slicer-grater and meat grinder.

I'd say you're most likely overloading the mixer. This mixer, and others similar in size, are frequently overloaded by people making pizza dough. If you are making dough, keep in mind the A-200's capacity is 9 lb. of 40% A.R. pizza dough, mixed for 5 minutes maximum. If you need to mix longer, the batch must be cut down even smaller, but I don't even know if you're mixing dough.

Try running the mixer unloaded (i.e. nothing in the bowl) for ten minutes or more and see if it gets hot. If it still gets hot, the motor's start circuit (varies depending upon age of the A-200; Hobart used numerous motors in the A-200 over the years, incorporating different starting circuits) most likely has problems. If it doesn't get hot when operating unloaded, then you're probably overheating the mixer by overloading it.

I don't beloeve mine will turn fast enough to do whipped cream quickly.

A number of attachments were available for the 4C, such as a juicer, a meat grinder, etc., all of which ran off the PTO on the front of the housing.  The only beater, however, was the wire one.  No dough hook was ever made.  I have been told that the motor didn't have the necessary power to run a dough hook.

Do you have more than one size beaters, if you do use the smalest ones that will rase the rpm DFD

Mine did almost the exact same thing one day. I have the Artisian Model, It would do it on any of the lowest speeds. Dont know if this will help you or not but I just ran mine the next day on all the way high with the spash guard on for making whipped cream for about 6 minutes full throttle and for some reason it hasnt went slow and shut itself off since then. Mine is about 7 months old. I called Kitchen Aid but their customer service all of a sudden seems to not know english worth a poo...

Try running yours on full blast for 5 minutes with something simple in the bowl. If its a 250 watt or higher make whipped water out of 2 cups of water and a tablespoon of cornstarch. Run it till you get what looks like whipped cream. Oh yea. Use the Balloon whip. The lubrication in the motor is supposed to last for at least 5 years but I have seen on numerous post's that if you run them on all the way for at least 5 minutes the oil will even out in the motor. Running the mixers at low speed alot will cause the oil inside not to move as freely since the motor doesnt heat up the oil in the gears.

Good luck.