I found this online, hope it helps! :
I am TOTALLY KIDDING! I just found that hilarious! There is a little lever inside the top that will allow you to adjust the speed. I was looking for instructions, since I am crappy at telling how to do it. There is probably a YouTube video. There is this:
The speed regulator is strange; upon opening the unit I expected a rheostat of some sort, but instead it appears as some type of clutch type mechanism (which I doubt it is). The speed lever moves a plate on the back in and out to regulate the speed, and was bottomed out with the lever at "2". There are adjustment screws, so I backed out the plate until the speed was at spec (60 rpm I recall, but do not quote me), tightened the set nuts and put it back together. That was last summer, and it still runs today.
The motor on "1" sounds a little uneven, which bothered me a bit, but I recall my mother's Sunbeam (circa 1965) to sound a bit uneven on low, so I let it go.
I consider myself fairly knowledgeable about the Kitchenaid's. I have a black Artisan in my house, and a pink artisan in the bakery, along with a green ultra power, and a cream colored 5 quart bowl lift one, and I bought a cream colored Artisan for my grandma to replace her Classic, and I have used my mom's Classic since I was 12 and told my Step-father to go get it for her (actually, me! I moved out when I was 17, 16 years ago, and I swear I have still used it more than her:-D ) I also have a 12 qt Hobart. I open them up when I feel I need to. They are very simple inside, hard to break. More like a car, mechanical, rather than a computer.
Each one is different. I swear, the Classic at my mom's was less powerful than the Classic at my grandma's. My Pink Artisan is faster than my black one. and My Ultra power is slower than my bowl lift mixer, and they have the same power. My Hobart is the next slowest on "stir", after the Green Ultra Power.
I always wrap plastic wrap around my mixer bowl when I add powdered sugar, unless I feel like cleaning up a mess. Add the Beater Blade to the equation, and Pink mixer will have less sugar in the bowl than on the table! I get a LONG piece of the commercial grade, wrap it around the bowl tightly, and wrap the other side up over the top of the mixer, and mix. I peel part of it back to add more once it mixes in, but it doesn't hold as tightly.