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Motorbike Macgyver
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384 Posts
Discussion Starter #1
I am contemplating the idea of draining the oil out of my K10 forks and just adding stiffer springs, or at least using less oil. I'm currently running 150cc's of 10w30 oil in each leg, due to the springs being so soft. So if anyone could tell me where to find stiffer springs that will fit, let me know. I can measure the springs if necessary.
 

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Motorbike Macgyver
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384 Posts
Discussion Starter #2
I've been looking at some springs online, and they cost more than I would care to pay. So I have another idea. There is a plastic spacer that retains the spring, the plastic spacer sit right under the bottom tree. It looks like if I moved these plastic spacers to the bottom of the fork leg, the spring would be more compressed. However, the plastic spacer would sit right on top of the fork seal. I'm not sure if this is good or bad.
 

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Motorbike Macgyver
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384 Posts
Discussion Starter #3
OK so here is what I did. I left the spring retainers where they were, but I turned them around. The reason is because they were a smaller outer diameter on one side to allow the spring to slip onto the retainer. With them turned around, the spring does not slip onto the retainer, therefore the springs are compressed more and the amount of travel is perfect. I will add 50cc's of oil back into each fork (drained when removed) to keep them lubricated internally.
 

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American Legion Rider
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23,631 Posts
You might just try a different brand of oil. The actual viscosity differs wildly by brand and weight as you can see on this chart.

 

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Motorbike Macgyver
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384 Posts
Discussion Starter #5
Well here is what I ended up doing. I took the spring retainer bushings and sat them on the bottom of the fork leg, they don't interfere with the seal at all. They compress the spring about a quarter of an inch. I then put 100cc of royal purple 10w30 motor oil in them, and they seem to be working pretty good.
 

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Motorbike Macgyver
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384 Posts
Discussion Starter #6
I'm much happier with the suspension now. The forks go up and down smoothly, and it would take going full speed at a speed bump for me to even come close to bottoming out.
 

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Premium Member
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5,645 Posts
You should know that adding fork oil effectively stiffens the springs, as the air space above the oil becomes a virtual spring as it is compressed. A smaller air space compresses faster than a larger one, so the effect is stiffer spring action.

BTW, for many bikes, Suzuki uses 10W fork oil, but as HC says, the weights can be widely variable, even within the same brands. Also, before fork oil was created, automatic transmission fluid was usually the recommend oil, since it resists breaking down from the forces in a shock better than motor oils, so lasts longer. As it breaks down, it gets thinner, so your shocks get softer over time.
 
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