YAMAHA YZ250F FRONT FORK AND REAR SHOCK SETTING

FRONT FORK SETTING

The front fork setting should be made depending on the rider’s feeling of an actual run and the circuit conditions.

The front fork setting includes the following three factors:

1.Setting of air spring characteristics

Change the fork oil amount.

2.Setting of spring preload

Change the spring.

3.Setting of damping force

Change the compression damping force.
Change the rebound damping force.

The spring acts on the load and the damping force acts on the cushion travel speed.

CHANGE IN AMOUNT AND CHARACTERISTICS OF FORK OIL

Damping characteristic near the final stroke can be changed by changing the fork oil amount.

: Adjust the oil amount in 5 cm³ (0.2 US oz, 0.2 Imp.oz) increments or decrements. Too small oil amount causes the front fork to produce a noise at full rebound or the rider to feel some pressure on his hands or body. Alternatively, too large oil amount will cause the air spring characteristics to have a tendency to be stiffer with the consequent deteriorated performance and characteristics. Therefore, adjust the front fork within the specified range.

Recommended oil

Yamaha Suspension Oil S1
Standard oil amount

295 cm³ (9.97 US oz, 10.4 Imp.oz)
Extent of adjustment

260–365 cm³ (8.79–12.34 US oz, 9.17–12.87 Imp.oz)

A.	Air spring characteristics in relation to oil amount change
B.	Load
C.	Stroke

1.	Max. oil amount
2.	Standard oil amount
3.	Min. oil amount

SETTING OF SPRING AFTER REPLACEMENT

As the front fork setting can be easily affected by the rear suspension, take care so that the front and the rear are balanced (in position etc.) when setting the front fork.

1.Use of soft spring

Change the rebound damping force.

Turn out one or two clicks.

Change the compression damping force.

Turn in one or two clicks.

: Generally a soft spring gives a soft riding feeling. Rebound damping tends to become stronger and the front fork may sink deeply over a series of gaps.

2.Use of stiff spring

Change the rebound damping force.

Turn in one or two clicks.

Change the compression damping force.

Turn out one or two clicks.

: Generally a stiff spring gives a stiff riding feeling. Rebound damping tends to become weaker, resulting in lack of a sense of contact with the road surface or in a vibrating handlebar.

FRONT FORK SETTING PARTS

Front fork spring

STD Spring rate N/mm		4.7
Type	Spring rate N/mm	Part number	I.D. mark (slits)
SOFT	4.5	BR9-23141-20	I-II
	4.6	BR9-23141-30	I-III
	4.7	BR9-23141-40	I-IIII
	4.8	BR9-23141-50	I-IIIII
	4.9	BR9-23141-60	II-II
	5.0	BR9-23141-70	II-III
STIFF	5.1	BR9-23141-80	II-IIII

: The I.D. mark (slits) is proved on the end of the spring.

REAR SUSPENSION SETTING

The rear shock absorber setting should be made depending on the rider’s feeling of an actual run and the circuit conditions.

The rear suspension setting includes the following two factors:

1.Setting of spring preload

Change the set length of the spring.
Change the spring.

2.Setting of damping force

Change the rebound damping force.
Change the compression damping force.

CHOOSING SET LENGTH

1.Place a stand or a block under the engine to put the rear wheel above the floor, and measure the length “a” between the rear wheel axle center and the rear fender holding bolt.

2.Remove the stand or block from the engine and, with a rider astride the seat, measure the sunken length “b” between the rear wheel axle center and the rear fender holding bolt.

3.Loosen the locknut “1” and make adjustment by turning the adjuster “2” to achieve the standard figure from the subtraction of the length “b” from the length “a”.

Standard figure

90–100 mm (3.5–3.9 in)

If the machine is new and after it is broken in, the same set length of the spring may change because of the initial fatigue, etc. of the spring. Therefore, be sure to make reevaluation.
If the standard figure cannot be achieved by adjusting the adjuster and changing the set length, replace the spring with an optional one and make readjustment.

SETTING OF SPRING AFTER REPLACEMENT

After replacement, be sure to adjust the spring to the set length [sunken length 90–100 mm (3.5–3.9 in)] and set it.

1.Use of soft spring

Adjust to decrease rebound damping force to compensate for less spring load. Run with the rebound damping force adjuster one or two clicks turned out, and readjust it to suit your preference.

2.Use of stiff spring

Adjust to increase rebound damping force to compensate for greater spring load. Run with the rebound damping force adjuster one or two clicks turned in, and readjust it to suit your preference.

: Adjusting the rebound damping force will be followed more or less by a change in the compression damping force. For correction, adjust to decrease compression damping force.

: When using a rear shock absorber other than currently installed, use the one whose overall length “a” does not exceed the standard as it may result in faulty performance. Never use one whose overall length is greater than standard.

Length “a” of standard shock

460.5 mm (18.1 in)

REAR SHOCK ABSORBER SETTING PARTS

Rear shock spring “1”

STD Spring rate N/mm		56
Type	Spring rate N/mm	Part number	I.D. mark
SOFT	52	BR9-22212-00 (Blue)	Yellow
	54	BR9-22212-10 (Blue)	Pink
	56	BR9-22212-A0 (Silver)	White
	56	BR9-22212-20* (Blue)	White
	58	BR9-22212-B0 (Silver)	Gold
	58	BR9-22212-30* (Blue)	Silver
STIFF	60	BR9-22212-40 (Blue)	Brown

* For BSB6

The I.D. mark “a” is marked at the end of the spring.
Spring specification varies according to the color of I.D. marks.

Spring preload adjusting positions

Spring preload adjusting positions

Minimum

Position in which the spring is turned in 1.5 mm (0.06 in) from its free length.
Standard

Position in which the spring is turned in 7.0 mm (0.28 in) from its free length.
Maximum

Position in which the spring is turned in 18.0 mm (0.71 in) from its free length.

: For the spring preload adjustment, refer to ADJUSTING THE REAR SHOCK ABSORBER ASSEMBLY.

SUSPENSION SETTING (FRONT FORK)

If any of the following symptoms is experienced with the standard position as the base, make resetting by reference to the adjustment procedure given in the same chart.
Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm (3.5–3.9 in).

Symptom	Section				Check	Adjust
Symptom	Jump	Large gap	Medium gap	Small gap	Check	Adjust
Stiff over entire range	✓	✓	✓		Compression damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
					Oil amount	Decrease oil amount by about 5–10 cm³ (0.2–0.3 US oz, 0.2–0.4 Imp.oz).
					Spring	Replace with soft spring.
Unsmooth movement over entire range	✓	✓	✓	✓	Outer tube Inner tube	Check for any bends, dents, other noticeable scars, etc. If any, replace affected parts.
					Slide metal	Replace with a new one for extended use.
					Piston metal	Replace with a new one for extended use.
					Lower bracket tightening torque	Retighten to specified torque.
Poor initial movement				✓	Rebound damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Poor initial movement				✓	Oil seals	Apply grease in oil seal wall.
Soft over entire range, bottoming out	✓	✓			Compression damping force	Turn adjuster clockwise (about 2 clicks) to increase damping.
					Oil amount	Increase oil amount by about 5–10 cm³ (0.2–0.3 US oz, 0.2–0.4 Imp.oz).
					Spring	Replace with stiff spring.
Stiff toward stroke end	✓				Oil amount	Decrease oil amount by about 5 cm³ (0.2 US oz, 0.2 Imp.oz).
Soft toward stroke end, bottoming out	✓				Oil amount	Increase oil amount by about 5 cm³ (0.2 US oz, 0.2 Imp.oz).
Stiff initial movement	✓	✓	✓	✓	Compression damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Low front, tending to lower front posture			✓	✓	Compression damping force	Turn adjuster clockwise (about 2 clicks) to increase damping.
					Rebound damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
					Balance with rear end	Set sunken length for 95–100 mm (3.7–3.9 in) when one passenger is astride seat (lower rear posture).
					Oil amount	Increase oil amount by about 5 cm³ (0.2 US oz, 0.2 Imp.oz).
“Obtrusive” front, tending to upper front posture			✓	✓	Compression damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
					Balance with rear end	Set sunken length for 90–95 mm (3.5–3.7 in) when one passenger is astride seat (upper rear posture).
					Spring	Replace with soft spring.
					Oil amount	Decrease oil amount by about 5–10 cm³ (0.2–0.3 US oz, 0.2–0.4 Imp.oz).

SUSPENSION SETTING (REAR SHOCK ABSORBER)

If any of the following symptoms is experienced with the standard position as the base, make resetting by reference to the adjustment procedure given in the same chart.
Adjust the rebound damping in 2-click increments or decrements.
Adjust the low compression damping in 1-click increments or decrements.
Adjust the high compression damping in 1/6 turn increments or decrements.

Symptom	Section				Check	Adjust
Symptom	Jump	Large gap	Medium gap	Small gap	Check	Adjust
Stiff, tending to sink			✓	✓	Rebound damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Stiff, tending to sink			✓	✓	Spring set length	Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
Spongy and unstable			✓	✓	Rebound damping force	Turn adjuster clockwise (about 2 clicks) to increase damping.
					Low compression damping	Turn adjuster clockwise (about 1 click) to increase damping.
					Spring	Replace with stiff spring.
Heavy and dragging			✓	✓	Rebound damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Heavy and dragging			✓	✓	Spring	Replace with soft spring.
Poor road gripping				✓	Rebound damping force	Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
					Low compression damping	Turn adjuster clockwise (about 1 click) to increase damping.
					High compression damping	Turn adjuster clockwise (about 1/6 turn) to increase damping.
					Spring set length	Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
					Spring	Replace with soft spring.
Bottoming out	✓	✓			High compression damping	Turn adjuster clockwise (about 1/6 turn) to increase damping.
					Spring set length	Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
					Spring	Replace with stiff spring.
Bouncing	✓	✓			Rebound damping force	Turn adjuster clockwise (about 2 clicks) to increase damping.
Bouncing	✓	✓			Spring	Replace with soft spring.
Stiff travel	✓	✓			High compression damping	Turn adjuster counterclockwise (about 1/6 turn) to decrease damping.
					Spring set length	Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
					Spring	Replace with soft spring.