I finished front side revalving (see here https://www.kawasakiversys.com/forum...9-post100.html
) and I am satisfied. Used Phoneman64 as starting point.. see link. Also original CST insreased to 42 by mixing Motorex 7,5 and Motorex 10.
shock was opened and some shims were removed and some are added for better flex. I did not had time to record all shims diameter and thickness and numbers. Guy who repairs shocks says it is by personal preference. I told him to remove some of them so I can get less fast speed compression.
In general from valve opening to the bottom: Few large shims (I would say 3, ONE REMOVED
) then few less diameter shims so large ones can flex. Then again few thicker large shims (I would say 5 pcs, 2 removed
), then some smaller shims.. After those smaller shims few low diameter shims added so whole stack can flex better.
New showa oil added, and probably rubber seal replaced. Nitrogen chamber pressure still holds ok..
Result.. similar ride feeling as front revalved side.. but still maybe harder then front side, but much much better..
I am 100 kg (220 lbs) and I think STOCK 16,7 kg/mm spring at stock shock is TOO STRONG. Even for me. and EVEN MORE for less weight riders.
First I set static sag to be 33% of total sag that is about 48 mm od 145 mm total. This is achieved by preload at position about 3 of total 7.
This setup gives FREE SAG of 18 mm. This free sag is too big which means stock spring is too stiff.
Instead lower spring rate spring should be used with higher preload to give identical rider sag !!!!
It is usually claimed that free sag should be about 5-10 % of total sag or 15-25% of rider sag. 18 mm free sag at stock spring equals about 37% of rider sag and about 12,5 % of total sag.
Also this is measured without full bags. Adding bags for the same rider sag .. preload should be increased. Adding preload makes affects the same rider sag and static sag, because bags are part of motorcycle, not rider. Motorcycle weight does not affect static sag, static sag is purely affected by rider weight and spring constant only if in both cases rider sag is set up correctly
According to this math says we can use this formula.
RW1 = Old Rider weight
RW2= New Rider weight
K1 = Old spring constant
K2 = New spring constant
deltaSS = difference of spring length between old static sag and new static sag
Shock travel 50 mm, Rear end travel = 148 mm, approximation = 1:3
3 = Wheel travel VS Shock travel ratio
(K1*3*RW2 - K2*3*RW1) / (K1*K2) = deltaSS
Well to make this more simpler I will use my results:
Rider sag = 48 mm /3 = 16 (shock spring travel)
Static sag = 18 mm /3 = 6 (shock spring travel)
RS - SS = 30 mm /3 = 10 (shock spring travel)
10* 16,7 kg/mm = 167 kg /3 Rider weigth 55 kg which rear end sees
RW2 = RW1 (still we do not change rider, maybe if I sell my bike hehe
K1 = 16.7 kg/mm
K2 = 14 kg/mm (new spring)
deltaSS = 3*RW * (K1-K2) / (K1*K2)
3* (16.7-14)/ (16.7*14) = 1,9 mm
deltaSS = 1.9 mm
delta SS *3 = 5,7 mm
Old static sag 18 mm
New static sag 18 mm - 5,7 = 12,3 mm -> 8,4 % of Total travel, or 25 % of Rider sag.... Result is within the limits..
Lets try 13 kg/mm spring:
deltaSS = 2,81 mm
delta SS *3 = 8,43 mm
Old static sag 18 mm
New static sag 18 mm - 8,43 = 9,56 mm -> 6.6% % of Total travel, or 20 % of Rider sag.... Result is within the limits..
Conclustion: When you make spring of lower rate, less kg/mm above formula gives change of Static Sag.. But to get identical rider sag as before we HAVE TO USE LONGER spring or same length spring with more preload (which is not possible without special spacers)
Formula for determination of how much spring should be longer (or how much spacers should be added) to get identical rider sag with new spring rate:
MW= Rear side motor weigth without rider. I took 80 kg, but can be measured putting rear end on scale
deltaL = (RW+MW )*3*(K1-K2)/(K1*K2)
For my case:
deltaL = (80 +55) *3 *(16,7-14)/(16.7*14) = 4,68 mm ---> new 14 kg/mm spring should be 5 mm longer.
Hopefully this all I wrote is correct