Carbs stuck open

This bike has been running again for 2 years. Yesterday I headed to the store and about a mile from the house it felt like I couldn't give it enough gas to pull out without stalling. I got it going and at first I thought I broke a cable, but the bike headed to red line. I killed it and pulled over. After some checking I found the throttle would move easily to about 3/4 around, and then I would see movement on the carbs.
They were stuck at almost full open. I managed to push them loose with a stick and limp home. They would stick if I twisted throttle all the way, but I can not see what was causing them to stick. I took them off the bike and they appear to work fine. Cable may need to be lubed but was not rusty or in bad shape. Could boot clamps have been hitting? Any ideas what it may have been?

Thanks,
Ken

Sounds like the throttle quadrant, or the part that the cable wraps around, is hitting something, possibly under the carbs? Only way to know is to pull the tank and operate the throttle while looking all around for something wrong.

Thanks for the reply DGA, I have lubed the cable and will take a good look as I put everything back together.
I will post back after I get it together, hopefully with a solution for others to learn from.
Ken

If your problem points to throttle cables and they are 30+ years old, I suggest getting a new set (about $15 for both @ Z1e). Take apart the throttle assembly up top, grease below the throttle grip, clean and grease the assembly per the FSM and insert new cables. I recently snapped my pull cable 20 miles out, it was 36 years old and when I replaced it could not believe how sticky the whole thing was. Surprised it worked. Also recommend changing the clutch cable while you are at it.