The base (clamp) shim supports the entire stack. Diagram 13 shows a typical stack with a 40mm main, 30mm separator and 20mm base shim.
Diagram 13
As previously demonstrated, the low speed circuit does not act independently of the high speed circuit if the separator shim is a larger diameter than the base.
Table 12 contains the stock compression valve stack for a 2004 RMZ 250. Using both the Shim Program and dyno, we will compare the stock valving with a 23mm base vs. a 25mm base.
As shown below, changing the base shim diameter from 23mm to 25mm has an affect on both low speed and high speed.
Stock comp valving - 2004 RMZ 250
11 - 40.20
11 - 40.20
34.12
34.12
30.12
30.12
40.25
40.25
38.20
38.20
36.20
36.20
34.20
34.20
32.20
32.20
27.20
27.20
23.30 base
25.30 base
Shim Program loads (lbs/in)
Shim Program loads (lbs/in)
def
load
.003
11.7
.006
23.4
.009
35.3
.012
47.3
.015
59.6
.018
73.4
.021
88.1
.024
103.3
.027
119.1
.030
135.4
.033
152.3
.036
170.0
def
load
.003
14.2
.006
28.5
.009
43.0
.012
57.7
.015
73.3
.018
90.9
.021
109.1
.024
127.9
.027
147.3
.030
167.5
.033
188.6
.036
210.7
% diff
122%
122%
122%
122%
123%
124%
124%
124%
124%
124%
124%
124%
11-29-05
04 RMZ 250
stk39s v4
11-29-05
04 RMZ 250
stk39s v9
Dyno force (lbs/in)
Dyno force (lbs/in)
ips
force
5
130
10
237
20
437
30
619
40
782
50
927
60
1053
70
1161
80
1250
90
1321
100
1374
ips
force
5
159
10
254
20
422
30
569
40
701
50
827
60
952
70
1084
80
1231
90
1399
100
1595
% diff
116%
121%
124%
125%
125%
124%
124%
123%
122%
121%
120%
Table 12
The Shim Program shows the loads to increase an average of about 23%, and the dyno shows the force to increase about 23%. The difference in these numbers appear to be very close, but this may just be a coincidence. The Shim Program load differences generally do not mirror the dyno differences. From previous experience, the Shim Program loads follow one curve, and the dyno forces follow their own curve. The curves do not always match. We are currently working to define the exact relationship between the program and dyno.
In this example, we changed the base diameter from 23mm - 25mm, and noticed an increase in both low speed and high speed forces. The low speed forces will also increase if any other shim changes are made to the high speed stack.
