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.
