The Handlebar clock  or Thermometer part # HBC fits on 1" bars and comes with all that you need to install it on your bike including a rubber spacer to fit on 7/8" bars. As you can see from the part, this will be a fine addition to your bike. Take a look at how the clamp is put together so you will put it back the same way.

When you loosen the  allen screw on the head, you can move the head left or right. Now move everything in the place that you would like it and tighten all allen screws. Clock is not in the holder all the way. After you set the time, you will put it in all the way. To remove the clock pry under the edge of the clock carefully.
Moisten a paper towel with Windex, or a similar product, then wipe it on the rubber ring around the clock. This will help you slide the clock in to the holder. Now turn the clock in the position you like and push it in place inward on the chrome edges of  the clock, making sure that the clock is firmly in place.  Make sure stem section is inserted first and then continue putting clock in place.  For your convenience we have included a spare rubber ring, for around the clock. Please, do not misplace it for later use. * Make sure clock is inserted all the way before riding.

This clock is waterproof, shock resistant and  the numbers will glow in the dark. Clock and temp gauge must be exposed to a light source to activated the glow in the dark feature. The clock base can be polished with a good chrome polish.
* When replacing the rubber ring make sure that the nub on ring does not go on top of the clock stem.       Handlebar clock part # HBC  1 Year Limited Warranty
Installation Instructions
Handlebar clock part # HBC
Last update 8/24/04
                        Marlin's Motorcycles
                        Call 1-800-777-5543
This is how you can tell what size you bars are.
You can cut a  7/8" ,1"  or 1 1/4  square out of your cardboard
then put it over your bars and how it fits over the bars will tell you what you have.