Ok, this is for a snowmobile. To be more specific, my 1976 Johnson Rotary Powered snowmobile.
Anyways, the throttle cable stuck at 3/4 throttle and will not budge. I heard somewhere a long time ago that you could lube a throttle cable. Is that true?
Parts for this are non existent, so i need to figure something out. 
Yes, you can lube a throttle cable. They even make special thingies you clamp onto the cable and squirt oil through. Very nice.
And none of it works if the cable is rusted and jammed. Then you simply replace the cable.
Bicycle shops and motorcycle shops are both perfectly capable of fabing up custom cables for your snowmobile.
Disconnect the cable at each end to verify if it's the cable or carb slide.
http://motionpro.com/motorcycle/partno/08-0182/
Your local m-cycle shop should have it with a small can of lube.