... Can't wait, I'm getting it with abs light on and diagnostics say tilt sensor not working, I've got 2nd hand one to fit ready, question is will the light go out if problem is rectified, or will it need to go to dealer to hav code cleared to turn light out. This is my first venture into theses bikes so prob got lot to learn 'bout them. Thanks
The tilt sensor (if it is the bank angle sensor) has nothing to do with ABS. So haste has already made for waste once.
You should get access to the Honda ST1100/A and/or Clymer ST1100 service manuals, plus the Owner's Manual. They tell you how to get the codes, and how to clear them out. Have a parts diagram, too.
I agree on first checking the fault code to circle down on the cause of trouble.
Could be as simple as ... a stuck modulator pump....
The stuck pump is common with the pre-1996 ABS models. I've never owned one of these post-1995 ABS models, but I'm not sure their modulator even has a pump in it. (If it does, I've never heard of the pump getting stuck.)
The part in question is very expensive; maybe that's why the bike was sold.
As the manuals will tell you, clear out the old codes, and verify the code again. (Older models had different codes; make sure you are using the right decoding table.)
Check, clean and reinstall your battery and modulator connectors.
Easiest thing to check, see this thread
https://www.st-owners.com/forums/showthread.php?80452-ST1100-Pan-ABS-problem
Check your electric power source, yes. But also use the ABS troubleshooting chart.
You should be able to ride the bike with the red light blinking; you just have no ABS.
But trying to ride it and troubleshoot it at the same time may not work. You may have to take the front fairing partially off and check that the pothole did not jar one of the electrical connectors loose.
You have no promises from us that the bike is safe to ride, and no estimate of how long it will take you to fix the ABS (assuming that you are willing to spend the thousands of dollars that it may need).