I'll share my story. A couple summers ago I was dealing with really stiff throttle return. Couldn't get snap back at all. I had to manually roll it back. And it was worse when it was colder. Not winter cold but late summer night cold. So not really cold at all.

I did everything. Lubed the cables. Checked for kinked cables. Replaced the cables. Inspected and adjusted everything on the carb end. Made sure the grips weren't too far onto the bars. Nothing worked.

Finally at my whits end I replaced the grips and that did the trick. They were the original grips from 1998 and they had become "out of round"

Just sharing my experience Incase my story can help someone else out with a similar headache

 

WD40 is corrosive on some metals. Aluminum is one. I use it as a lube for an Hilti air nailer on one job. 3 months later I tried to use it and it would not even huff much less drive nails.

Stick with a real cable lube.

 

I've had success with spraying teflon into the lines.

 

I use Tri-Flow.

 

Wow this thread is till going?
Maybe this will help?

 

sorry,more internet bovine excrement...
http://wd40.com/files/pdf/msds-wd494716385.pdf