Changing fork seals on a 2007 990 for a friend of mine and I've run into a problem. When I turned the fork upside down to drain the oil the following fell out: Which is according to the parts diagram is a rebound needle. This will be my third set of 990 forks that I have changed the oil or seals and have never seen this part fall out. It did not fall out of the other fork and that one went back together just fine. So after it fell out I put it back on the rebound adjustment rod put it back in the catridge. It looked like it would work, but when bleeding the air bubbles out the oil comes up through the catridge spindle which pushes the rebound rod up. I know you are not supposed to have oil coming out of there. Any suspension guys out there know what is going on? I really don't want to screw anything up.
The bright side is that at least that rebound valve is not rusted and corroded and stuck in the rebound tap. I would disassemble the cartridge so I could get to the entire rebound piston assembly and verify everything is ok by looking. The valve goes in the top of the assembly and should be a snug fit from the o-ring on the valve fitting inside You also need to make sure you did not pour any oil down the middle of the cartridge. This area should be dry on WP forks. If oil got down the middle of the cartridge tube you will have chronic oil leaking out the rebound adjuster knob on top of the fork cap.
I have disassembled the cartridge, but did not separate the mid-valve from the cartridge. It did not look like an easy task. The rebound valve definitely does not fit snugly which looks like it might be my problem (o-ring???). I know to keep the oil out of the center cartridge which is what freaked me out in the first place when oil started coming up through there. Going to try and replace the o-ring on the rebound valve and see if that's it.
I changed my fork seals last week and that fell out of one of the tubes while draining. I freaked out. Turns out, you just slip it back in. No big deal. Just make sure the rod seats properly before buttoning everything back up. ben
You need to make sure that the needle is pushed in fairly tight and not just dropped in. Essentially so the part with the oring seats and makes a seal. Once you assemble the forks this will be held in place by the top cap rebound adjuster.
If it's not, or if the rebound adjuster rod isn't seated correctly on the needle the rebound rod will protrude higher than ~ 1/4" above the threaded damper rod. A small amount of grease on the o-ring will help here. Don't put the cap on like that. You should be able to push down on the rod and ascertain the needle is seated correctly by feeling the spring compress.
Got it. Luckily the FEDEX guy showed up today with a set of well used EXC forks that I got off of ebay for another project. Used the needle valve/spring from the donor forks and they went back together as they should. The spring from the donor needle valve was slightly different. Of course when I pulled the o-ring from the original needle valve it went shooting off across the garage never to be seen again! Lucky to have the donor forks on hand. Thanks for all the help. I now know enough to be a little less dangerous when working on forks.
