Sounds like your motor needs a fan...... 
You can make one for that, too out a bit of sheet metal. Or direct some of the main fan flow somehow over the motor case.
And if you want to get really tricky, a housing to direct the inlet air to your main fan after passing over the motor case would preheat your blast a little....
That blue lump on the back of the motor covers a fan. I think that fan is designed to just blow air over the outside casing, even though there are holes in the back of the thing (there aren't any through holes for air flow, and the ones I added don't seem to be doing much anyways).
I was considering making just the inlet of the blower on the same side as the motor so that air pulled in would come from it's general direction. The motor is face mounting only though and I sorta want to try and make something a bit professional looking (paint n all!) rather than something jury rigged with scrap steel brackets and jubilee clips.
As always there's problems every step of the way and now my jigsaw blade is drifting 10 degrees but I think if I bolt a secondary foot to the thing at 10 degrees, it'll hopefully keep the blade straight. I don't particularly like jigsaws much and don't particularly want to have to buy an expensive one. As a side, I'd bought a pack of 'cheap' blades from a real hardware store and i'm amazed by how well they hold together. By the time I noticed the blade was wandering (because it was sparking so much!) it was bent about 45 degrees. And then it sprung back to straight when I removed it. I'd previously been trying to use brand name diy store blades and they just lost teeth and snapped all the time, and cost about 10 times as much for a pack of 2. It's amazing what those diy stores manage to get away with.
