It sounds like the governor on the motor may be shot and depending on how handy you are you could find another Model 12 that is working and exchange the innards. Model 12's are very common, $5 to $10 bucks in most thrift stores. You could also try oiling the mixer. There are 4 spots that need oiling, I use sewing machine oil. The first spot to oil is on top of the machine at the back right in front of the mixer dial, one drop only. The second hole is right under the handle on the top, two drops. Slide the handle over and you'll see another little hole, put another two drops in there. Lastly, put a drop of oil into the power take off connection on top of the machine. Hope that helps.