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I have these forks on a second hand bike i brought for my wife. They where originally at 140mm but I dropped the travel to 120mm. They had this top out know knock before and after, as soon as it extends back to full travel it knocks, its rather annoying on fhe trail, sometimes it seems to get better and other rides seems alot worse. if I let all the air out and them pull up on the csu they still knock so leading me towards the damper? Anyone had this before or any easy fix?
Attached a picture and short video, hopefully the links work.
https://flic.kr/p/2jXGfhw
I had somethign similar, but the opposite, with an X-Fusion Slant fork. It is internally adjustable from 100mm to 160mm travel. However if you go beyond 130 or 140mm (I cant remember which), you also need to buy a longer rebound assembly. When I extended from 130mm to 160mm I started getting a top out knock when testing in backyard. It was the rebound hitting full extension. Afer purchasing and installing the longer rebound assembly, the topout knock went away.
Maybe you've got the reverse issue? Although I was led to beleive that the longer rebound assembly would work for all travel ranges.
Is there a small negative spring in there? If that's missing it can cause a top out knock, I had the same thing with some X Fusion Vengeance coils that did it so I added a small negative spring from some Suntours which cured it. I wanted to bugger about with them anyway to lower them a bit so it seemed like as good a time as any to fix the top out knock while I was in there.
Interesting, have what sounds like the same problem on some Metric R forks (160mm). Have been like it since new and it's really annoying, clunks everytime you lift the front wheel, jump etc. And the forks wobble and quietly knock if you rock the bars backward and forward.
Forks went back under warranty for a different issue and still did it when returned, the warranty has since expired and it'll be £100 + courier + parts to check it checked out.
Interested in knowing how hard they are to take apart and check/fix the negative spring? Is there a guide anywhere?
There is a long thread over on mtbr about servicing x-fusion forks, answer might be in there.
Had high hopes for the x-fusion forks but they've been awful from the start, far worse than any of the Fox, Rockshox or Suntours I've owned.
Interested in knowing how hard they are to take apart and check/fix the negative spring? Is there a guide anywhere?
There's no guide as such but they're really* similar to Suntour forks inside and I'd messed about with enough of them to know how the X Fusions [i]should[/i] have been working and was shocked and also appalled at the lack of negative/top out spring. I sold them shortly after I'd fixed them and went back to Suntour which are loads better (in my opinion). I put a spare negative spring between the underside of the piston and the part that holds the airshaft in place at the bottom of the stanchion (which is held in with a Spirolox clip** in the forks I had but is held in with a threaded piece on Suntours).
Once I'd sorted them out (top out spring and reduced the travel to 140mm) they were really good but not good enough to keep when some bargain Suntour Aurons came up.
* like I-can't-believe-these-aren't-Suntour similar.
** you'll need a set of dental picks to get it out.
Small update on this. I had a listen to the knock with a stethoscope today, it seems to knock from both legs but possible the air side was the loudest of the two so decides to strip them down and inspect both sides. I couldn't see anything on the rebound/compression side, everything is tight. The air spring is a cheap setup the piston just rests onto of the shaft, the only thing I found was the heat shrink on which I suspect is a negative spring was abit loose, it can make a tap noise when it hits the plastic collar which is help inplace with the c clip, this does the travel adjust.
Anyone see anything I can't?
But of an update incase anyone else has this issue.
The issue was the heat shrink on the top out spring. While it was still in place it was baggy. I got some clear heat shrink from j tech and put it on and its now knock free