CIM's Over loaded/Heated

[merybar]

Trying to see if any of you have any thoughts on this, we are at a loss of what to do. We decided that our belt driven drive with fisher prices were not quite quick enough so we made some modifications. We left our Belt and large pulley on there but attached a sprocket to the back which leads down with a chain to the CIM, with a small sprocket on the CIM (Very small, as small as we can get) We reduced the CIM's RPM's down to about 675 (increased from 120 from the Fisher Prices). Tonight when we finished it up (we are a Michigan team) It ran amazingly without load, and with the trailer and running around it did great, however when we started to hold it up the CIM's Got hot, after about 15 mintues of testing they were smoking hot. (steam was leaving a CIM) So this leads me to the question, any suggestions or ideas to fix the problem? Any ways to cool them off? Thanks everyone,
Matt