+1 on this. Dont try to use the cable to jump start you will melt it or worse in a short time. But I have used this tecnique quite often with good result, make sure you leave the donor bike running!
Originally Posted by FakeName
I've made one similar and have used it. I won't try it as a "jumper cable" but will hook two bikes together and let the donor bike run for a while to give a little juice to the weak bike.