I changed the fork oil today and the rebound damping valve and spring plopped into the oil. Can anyone tell me which way round they go back into the top nut please.
Not sure what you mean. The rebound damping valve is inside of the cartridge. The compression valve is at the bottom of the cartridge. What part did you plop into the oil (besides the spring)?
Your best diagram may be the parts breakdown diagram on nearly any Yamaha parts website. Here's one of my favorites
Note: that the spring generally needs to be removed during the oil fill to get the correct oil level, anyway.
Are you saying that you disassembled #37? If so, I've never done that as there is no need to. Just loosen #41 lock nut and spin the entire #37 off the damper rod.
The only spring in the cap nut would be to create the detents for the adjuster knob (clicker).
Edit - Wait, Did you disassemble the damper cartridge (31) and removed the rebound valve from the bottom end of the damper rod? There is a short needle and spring inside the rebound valve for the adjustable rebound orifice.
It's been a while since I rebuilt my fork valves. Let me see if I can a find a breakdown of the cartridge somewhere. I remember it seeming intuitive.
It was part 37, I didn't disassemble it, the valve and spring just fell out when I took it off so I din't have a chance to see how it went in. I have looked for a drawing but the Yamaha drawing doesn't show the valve and spring.
I put the pointed end into the top nut followed by the spring which sat in the small rod the protrudes slightly from the damping tube.
I've been out for a ride today and everything seemed normal, so I think I must have got it right.
Never seen anything like that on the prior version forks. Having a pointed end at the top sounds wrong to me. Did you buy the bike new? Any chance someone else has worked on it and assembled it wrong? There are no hydraulics in the top nut. The oil level doesn't go that high.
I imagine that you pulled out the long skinny rod from the middle of the damper rod, right?
At the bottom of that rod is the rebound valve and the adjustable orifice. It has a short needle sitting on a spring at the bottom of the hollow shaft that is pushed down to variably block off the orifice by the long rod from the adjuster screw mechanism on the top nut. Is it possible that the needle and spring came out from the bottom of that?
I've changed the oil on lots of 1st and a few 2nd Gen bikes and that needle and spring were captive at the bottom of the hollow damper rod, but maybe they changed something about that on the 3rd Gens?
Here's a picture of the damping valves from a stock 1st Gen removed from the cartridge, but in their normal orientation top tp bottom.
The brass pointy thing at the top is the adjustment needle for the rebound damper valve. On the 1st Gen the larger diameter of the valve is what holds it captive inside the rebound valve when the damper rod is screwed into it, and is what bears against the the spring below it.
The spring goes under the needle to hold it up (open), and the needle gets pushed down to close off the orifice by the long rod from the adjuster at the top.
I assume that yours would be the same (spring first,then needle pointy end down, then the long adjuster rod on top) but don't know what the spring would bear against on the needle. If you can snap a photo of what you have on your 3rd Gen that might help.
Thank you for all your help. I've got it sorted now, spring and valve slid into the tube, what a numpty I am
Went out into the garage got the tools out whipped off the fork put the valve in the right place and the right way around put the tools away all in an hour and five minutes. I have pulled the forks of so many times now I could do it in my sleep.
Glad you got it sorted. I would still have liked to see what the valve needle and spring looked like for future reference, but I guess it must just be the same diameter as the longer rod (to fit down the tube). But still don't know how the spring wouldn't be in the way down there.