How is flow controlled in damper forks

zoommx · Jan 19, 2004

The forks on my 490 feel like they have water in them instead of oil. I just put in new bushings, seals and 10 wt oil. but they have very little dampening. is the control of the oil flow determined only by the size of holes in damper rods? I was wondering if the previous owner drilled out the holes. Maybe they even drilled them out alot and put a cartridge fork emulator in and removed them before selling to me! :| I know these won't feel too good, but they arent even close to feeling right, not even as good as that older 100 I have. Want to get this ready for a Hillbilly GP race in Febuary in the 'vintage' class.
Roger

marcusgunby · Jan 19, 2004

Could try a 15wt oil.

weatie181 · Jan 19, 2004

zoommx
Could you ask the past owner if they did modify the forks? Or, it is usually obvious when the compression damping holes are enlarged for an emulator. Some times stock damping rods only have 4 comp. damping holes drilled, and emulators take six, (more fluid flow thru the holes the better), cause' the emulator does all the damping. The compression holes are on the bottom of the damping rod, and rebound at the top. Marcus has a good point of trying a 15 wt fluid, but because the rebound damping is not adjustable, it is a slave to the weight of the fluid! The heavier the fluid, the slower the rebound will be. So, look before you leap...:)

zoommx · Jan 20, 2004

Good point on rebound dampening. It could use some more. But as little compression dampening as there is, I cant imagine weight change helping much. So there aren't any moving parts that could be stuck open I take . I didn't think there was; I put emulators in my old kdx, wish I still had it to swap em to test. If I ever have any free time I'll take em apart to inspect the holes. Been working around 80hr/week, the next 2 weeks, probably 84. Then out of town for training. Oh well, better now than in the spring.

dirt bike dave · Jan 20, 2004

Raising the fluid level will dramatically improve bottoming resistance, so that might help it become a little more rideable. Stiffening the springs and/or adding more preload also won't fix the lack of damping, but might improve the fork overall.   You can cheaply stiffen the existing springs by cutting off some coils (make sure you aren't going to coil bind).

The long term best fix is probably to add some emulators.  Or fill in the existing holes in the damper rod and re-drill with a smaller bit. 

How is flow controlled in damper forks

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How is flow controlled in damper forks

zoommx

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