Measuring drive belt tension is a relatively simple thing to do.  Belt tension is actually set by measuring the amount of belt deflection when a 10 lb force is applied.  On the XR1200, the belt deflection is measured in the middle of the bottom segment of the belt.  An experienced rider or mechanic can get a good feel for the belt tension by depressing or twisting the belt.  If you are not familiar with the feel of proper belt tension, or if you want to get an exact measure of the deflection, a belt tension gauge is a great tool.  Here is how you set belt tension using a tension gauge...

Measuring belt deflection/tension  is straight forward.  On the XR1200 the tension gauge is placed against the bottom of the belt at the mid point between the idler wheel and the rear pulley.  The position of the gauge is noted, and the spring plunger on the end is depressed until it reaches its mark for 10 lbs of pressure.  (Gauges like the one that I am using have a small rubber o-ring that helps identify the 10 lb mark.)  One then measures the distance that the belt is depressed with 10 lbs of pressure applied.
The leading edge of the lower belt guard of the XR1200 actually has a measuring scale marked on it.  One can use this scale to measure deflection.  The tension gauge also has a measuring scale marked on the side of it.  Since I wanted a precise measurement for my notes, I removed the lower belt guard so that I could measure deflection at the exact midpoint of the belt.  To measure deflection, I held a part of my Combination Square against the swingarm as a reference point, and measured the deflection as I depressed the tension gauge.  I am also probably excessive, since the spot where I work in my garage is near a toolbox, and I could brace my head against the box to hold a constant viewing angle as I pressed the gauge.

There is not much difference in these pics, but here you can see where I marked the midpoint of the belt, and am using the head of the Combination Square as a reference point for measuring on the scale on the belt tension gauge.

Deflection Measuring Tools

The belt deflection should be between 1/4" and 3/8" for the XR1200.  Personally, I'll set a stock rear end at 3/8".  And, because a raised rear end pushes the swingarm out of its design range for the idler wheel, I'll set a XR1200 with riser blocks to about 5/8" of deflection - which will keep the belt deflection looser than 1/4" through the movement of the swingarm.

In this pic you can see where I am using the end of the head off the Combination Square to read a zero point on the tension gauge ruler scale.  To measure the belt tension, I'll press the rubber plunger on the end of the tension gauge in until the rubber o-ring on the plunger just touches the body of the gauge, and measure the distance that the tool moves on the scale on it's side.  Simple enough...

Measuring Deflection

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