Yamaha FZR400 1988-1989 Service Manual page 402

2) Have a friend hold the front end of the
bike. Sit on the bike in your normal riding
position. It is also a good idea to have your
normal riding gear on including your
helmet. If you normally carry luggage on
your motorcycle, leave it on the motorcycle
for this measurement. Push down on the
rear of the bike then let it settle. Measure
the distance using the same points as
above. This is L2; write down this
measurement.
3) Rider sag = L1 – L2. On a street bike this
should be 25% to 35% of the total wheel
travel, or typically 1" – 1.5" (25-35 mm).
On a road race bike this should be ¾" - 1"
(20-25mm). (Your motorcycle owner's
manual will tell you the total wheel travel.)
4) To set rider sag to the correct amount, use
the "C" wrench provided and adjust the
preload adjuster nuts on top of the spring.
Tighten the nut onto the spring to decrease
rider sag; loosen the nut to increase rider
sag. Repeat steps 2 through 4 until the
rider sag is in the desired range.
5) Push down on the rear of your motorcycle a couple of times and let it settle with no rider on board.
Measure using the same points as before. We will call this L3; write down this measurement.
6) Static sag = L1 – L3. The static sag should be between 0.25 - 0.5 inches (7-13 mm).
The following chart will enable you to determine if your spring rate is correct. The measurements given
are a guide only; there are no absolute settings that you must stick to.
Rider Sag
Appropriate Range
Appropriate Range
Figure 1: Measuring from the rear axle to a point
on the chassis directly above the rear axle
Static Sag
Too Little
Too Much
Spring Rate May Be:
Too Soft
Too Hard
6