The answer is in this thread, 2nd post down;LDCSTEVE, I have a 08 gl1800 also. I understand how to make the adjustment. I wonder how you got the plastic cover away from the cable. this is the piece that is attached to the ignition key area and further forward right near the top cowl.
Yep, I did all the work removing the cowl, etc etc. Backed off about 3/4 turn and put it all back together... Now I have the 2 or 3 mph increase, and it does jump! Now I am trying to find the enthusiasm to do it all over again. The bright side of it is that I am getting quick at it.I assume you are refering to the piece around the ignition? If so it just pops off. Use something under it that wont scratch. I use an old feeler guage, slide it under and it just pops off. Use the feeler guage under the right and left cowl trim as well, slides under without scratchng.
By the way I tried the "Honda" way of adjusting the lag. Turn until the RPM's increase the back off 3/4 turn. You need to back off at least 1-1/2 complete turns after the idle increases or the bike will speed up when you engage it then back down to the speed you selected. Could be dangerous if you are notexpecting it.
When adjusted correctly it should only be about a 1/2 second lag. It took me three times to get it right, so ride the bike before you put everything back together.
Hope this helps.