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Discussion Starter · #1 · (Edited)
Hi guys, I just serviced our JUnit 24" Expert fork and figured I'd share the experience. I didn't video the whole thing but the documentation is solid and I'll fill in the gaps. So far the servicing has REALLY made it awesome. Our fork had two seasons on it and it was really hurting for a service. It took me a couple of hours but was pretty easy.

Service Materials and Tools

Service Guide:
https://hayesbicycle.zendesk.com/hc/en-us/articles/360037789834-JUNIT
Machete JUNIT Rebuild Service Kit 37$:
I had almost all of the basic tools (listed in documentation) but needed a few extras and found them cheaper and manitou's custom kit:

24mm Flat Ground Socket: 10$ Amazon.com : Park Tool Flat-Faced Socket Silver, 24mm : Sports & Outdoors
(didn't work well) 8mm thin wall socket: Amazon.com: OEMTOOLS 22272 8 mm Metric Deep Socket : Everything Else

Tool Notes: NOW...the 8mm socket I purchased wasn't thin enough to fit down into the lower when unscrewing the nut at the end of the rod. Manitou's is way thinner. You can get their specific tool kit below and maybe it works better (FYI you don't need the cassette tool part unless you have the IRT version of the fork, not the expert). Regardless I didn't need it and made due without it, more on that later. Also you'll want some syringes with tubing to add and remove cc's of oil.

Oil: I used Fox 5wt /w Teflon Oil for the damper 20$ a quart I think. Viscosity on the charts is supposed to be very similar to the Motorex than Manitou calls for. Manitou confirmed that this was fine. That's the same oil I used in my Grip 2 damper on my Fox 36. I used Caster Synthetic 5/40w 10$ motor oil for the semi-bath. That's what works I'm told. Don't get something with any detergent in it.

General Service Notes
  1. When unscrewing the footnut on the airside with the 8mm thinwalled socket...there is some nuance there. At first its easy as the fitting for the nut is outside of the lowers. But...then it sucks down into the lowers and my socket couldn't reach it but the lowers weren't fully unthreaded yet. I used the end of the schader valve and just unscrewed it with my fingers. They mention that you could use a 4mm hex to do it this too but its NOT intuitive at first at all on how that works. The middle of the schrader valve has a red pin in it. If you carefull depress that red pin with the 4mm far enough, the 4mm fits into the internal hex fitting inside of the valve and allows you to do some light screwing/unscrewing until the fitting is threaded/unthreaded enough for the 8mm to work. Its fairly easy once that concept is clear, but its not documented well. You'll use this technique moreso when reassembling the lowers.
  2. I had to work pretty hard to get the dust seals out with my plastic pedro's lever. It was bending the lever pretty good. If you work around it in a circular pattern, its easier. Should have done that first.
  3. When I inserted the new seals, my 32mm socket fit just right around the upper ring of the seals and pressed them into place REALLY nicely. YMMV
  4. I soaked the dust wipers in the 5/40 semi bath for a while to ensure they got lots of oil in them. The fork was bone dry when I disassembled it. I also put an extra couple of cc's of that 5/40 oil down the top of the stanchion once the air rod was assembled back in place later on. Fox does this so I figured I'd do it. Should work fine with the slick honey (fox does this as well).
  5. As I went along, I found, matched up and replaced as many O-Rings as was feasible and easy. They looked fine but I was doing it so why not.
  6. Pro-tip: Wet polish anything that moves with 1500grit sandpaper. I would heavily coast the stanchions and the piston rod (where things slide) with oil and then wet sand 5 times with a small piece of 1500grit. I'm told this makes a big difference. So far so good!
  7. When I disassembled the top-cap of the damper...the damper assembly was supposed to all come out together, but instead just the top cap came off. It had become unscrewed from the rest of the damper (black and red elongated assembly). There was a silver metal rod that was down the middle of the embedded damper assembly as well that was unthreaded. Here is how I got it back together. I screwed in that metal rod using a hex. Then I placed the top cap over the damper and screwed it in just a bit (its fits around the black outer threads/fitting. Then I used the end of the rod (below the stanchions) and twisted it enough to thread into the top cap. Then I gently pulled it all out and screwed the damper to the top cap fully using a small wrench and light pressure. Worked great and I was back to the manual after that.
  8. When adding the oil into the damper, it was interesting but easy enough with a small ruler making a mark on a chopstick and then using that to gauge how much I have in there. Just make sure to read the instructions.
  9. When putting the lowers back on, its really easy to get the lips of the seals to fold over. You gotta be smooth with this.
  10. After assembling it back together its difficult to get the airside rod to thread back into the lowers because the rod is down inside it. Once you press the lowers close enough to the rod, use that 4mm again (inserted into the air rods schrader value via depressing the red pin) and it'll screw right onto the lowers just fine.
  11. Note that when you air it up at all, you always want to really screw down the shockpump so that it depresses that pin enough to fill both the positive or negative chambers. Some pumps just don't work. You'll notice when this happens because the fork will suck into itself and not fully extend.
  12. We don't get proper sag using the PSI on the charts and have to drop under just a bit. My 70lb kid runs like 35PSI on our 145mm travel fork to get 20% sag and a click or two of compression and it works great (I think). There is a really significant bottom out bumper too.
So there it is, better than new. Its really awesome that this fork is so well supported as I've got more than one kid and it needed it badly. The other forks we've had that Spawn/trailcraft/prevelo use had no documentation at all and didn't really get better with servicing since the damper was a spring sort of. The JUnit stuff is so far beyond the competition and the servicing support of it is just another example of that. Hope this helps, feel free to ping me with questions.
 

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I'm not going to agree on your wet sanding. But one way to reduce friction on these forks is to undersize the main air piston seal. This has trade-offs, the fork may stick down in the cold and your seal won't last as long before it needs replaced.
Simply take the main air piston seal and fit the next size down. It stretches thinner which reduces squeeze on the seal and makes it slide easier.
 

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Discussion Starter · #3 · (Edited)
Thanks for the comments, always great to hear from the expert! Fwiw the wet sanding was recommended by Manitou product owner, apparently that's what they do for their sponsored riders. I don't have any opinion, tho I did it. Wet (very wet) sanding with 1500grit is def more of an automotive polish type thing than hardcore sanding by any means. Apparently if done very lightly it has an impact (I was told) to remove irregularities out of the shaft and stanchions. The fork is pretty damn smooth now that's tuned up and lubed. I feel like there was a tiny bit of mid-stiction in the past (when it was still newer)...however there is NONE of that now. Likely just the service and grease but maybe the sanding/polishing helped. Fwiw I even have to service my Fox forks immediately when they are brand new to get all the excess grease out (pretty nutty).

Very interesting on the piston seal! How cold are you talking about and does it just stick at first or frequently? We ride in 40-50d F often here in the PNW but not usually freezing temps. Is there anything else I can do to the fork? Its just the Expert version, not the newer Pro version with the updated lowers etc. Wondering if there is a better airspring or anything else I should/could do.

My younger guy (6yr) has the 20" on his hardtail. Its running really lower pressure but seems to work really freaking well but any tips on getting that to work better are welcome. I did tune the amount of travel via "attaching a shock pump and pressing the fork into the lowers" in effort to reduce travel by 20mm-ish. I assume that's ok.
 
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