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Guys,
I lost a non-trivial amount of oil through a leaky fork seal and I want to add some oil back in now that I've fixed the seal with a Risk Racing Seal Doctor (excellent product!).
I tried adding oil via the air bleed ports with a small plastic 30-cc syringe, but I can't seem to get any oil to actually go into the forks.
Any tips on how to add oil into forks without taking the fork caps off?
Thanks in advance!
Remove the bleed screw, compress the fork, insert the end of the syringe, slowly extend the forks as you squeeze the syringe.
Get some blunt needles.
https://www.amazon.com/Dispensing-Connector-Industrial-Syringe-Applicator/dp/B08ZKLBG82/ref=pd_bxgy_img_sccl_1/130-0344633-0568074?pd_rd_w=P7zUz&content-id=amzn1.sym.26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_p=26a5c67f-1a30-486b-bb90-b523ad38d5a0&pf_rd_r=J281BESQR12CKHTGWNRQ&pd_rd_wg=AslgA&pd_rd_r=470f5294-6f27-4234-aa40-57613ee37ee9&pd_rd_i=B0BLCLBRFF&th=1
One of those syringes for bbq.
Appreciate the great feedback guys - will try some of the above shortly.
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Dont fully cover the bleed hole with the syringe. You need to leave room for air to escape.
Not if you compress the forks, and slowly extend them as you squeeze the syringe, the suction will help pull the oil into the fork!
You’re trying to add oil to the outer chamber but the problem is the bleed hole leads to the upper space of the inner chamber. Yes, there are weep holes and eventually, hopefully, after some strokes of the fork the oil will migrate out the weep holes to the outer chamber. But this is not the ideal way to do it. Especially for an amount as high as 30cc. If your dead set doing it this way, do 10cc, ride a little, and repeat twice more.
A better and easiest way, put the bike on a stand, remove the bars, loosen top clamp pinch bolts, loosen top fork caps, push the front of the bike down so the inner cartridges come up out of the tubes. Now you can add the oil directly to the outer chamber.
It’s pretty easy to just unscrew the cartridge and slide the outer tube down a little and just shoot some in. I’ve done it through the bleeder but I wouldn’t do more than 10cc at a time between several strokes.
Kind if an old thread but I used a
Noleen fork oil syringe today and put 20 cc's in each KYB SSS bleed hole easily, problem is now I only have 10.5 inches of travel. I'm confused on where the oil went, I though it was going into the outer chamber but I am reading there is an air pocket it goes into? Can I just take the forks off put them in the soft jaws up side down the remove the bleed screw and remove the oil like that? Is the oil in the air chamber or did it make it's way to the outer chamber? I rode about 45 laps today and tried to bottom the forks on purpose and it's still 10.5 inches of travel of course. It's on a 2023 YZ450f. I feel stupid asking but trying to read up on it it's not clear what's going on to me other than too much oil in the forks lol 
Thanks.
I guess I should add I am running the Technica Enzo long spring tubes. ENZO said run 250cc which is where I started before I added the 20 cc, Technica said run 330 cc in an email when i asked what they recommend with the tubes but I think we got our wires crossed. Last time I added 10cc on top of the 250cc and it was perfect.
So, you are only supposed to have 250cc with those long tubes but you now have 330cc? If that's the case, you are likely hydro-locking and that's what is limiting your travel. The bigger tubes displace much more volume than the stock ones so you are now taking up all the available internal volume before getting a complete stroke. At this point, I would just completely open up the forks and dump all the external oil, properly bleed the cartridges, and then reset the outer chamber oil level to remove any guesswork.
No sorry for the confusion, I added 20 to each leg for a total 270 that is in there now. Good advice though. I guess I can reuse the oil? It was a fresh build with all new bushings and seals and only has like 4 hours on it.
OK, gotcha. 20cc through the bleed hole at one shot may have been too much and it's now hydro-locking in the upper compression assembly area of the cartridge. You really need full travel of the fork in order to push all that excess oil up to the weep holes so it gets to the outer chamber. if it didn't happen after 45 laps, taking the fork apart and getting that extra oil out of the weep holes and resetting the outer volume might be your next step. You probably can reuse the oil at 4hrs if the forks were clean when assembled.
I pulled 15cc's out with my Noleen syringe. I hope it works out okay I spilled may one CC. I didn't have extra oil so I did it the lazy way. I want to ask you some questions since you know more about this stuff than me. So the oil I pulled out came out of the part that was hydro locked I am hoping LOL? When I turn the fork sort of upside down could oil run into the weep hole from the outer chamber and fill it up more? I understand about pumping the cartridge and getting the excess out and the weep hole when putting it all back together, but last time I was rebuilding it I got done bleeding the excess and inverted the cartridge not thinking and more oil ran out of the weep hole but that was just excess? Once I screw the compression valve assembly into the cartridge it's sealed and no oil can run out if I turn it upside down? I hope that makes sense. Pretty dumb questions but I want to understand what is going on. I made a video for the heck of it.
You can buy plastic syringes of amazon for cheap. They won't last longer than a week cause the oil will make the rubber swell unless you get good ones. You can throw a lil rubber hose on it too to snake it into the bleed hole. I always compress the forks with a tie down from the bars to the front axel before connecting the hose to the bleed hole.
Then with the bike on the stand, the hose in the hole, the plunger removed from the syringe, release the tie down.
When you stick the syringe into the bleed hole, yes it's going into the area where there should be no extra oil. However, you are correct that when the fork is inverted oil from the outer chamber could potentially enter the weep hole into the upper part of the cartridge. Really, there is only 1 true correct way to ensure you got this all right - Open the fork up and start from scratch. At the end of the day, sometimes you just end up chasing your tail when you try to take shortcuts.
On your question about the excess on last rebuild, that area above the piston has all kinds of nooks and crannies... oil gets hung up in there and it can take some time and patience (and maybe some compressed air) to get as much out as possible. No extra oil should accumulate in there when you put that cartridge upside down unless it's not sealing properly. But, like I said, it's more likely there was just some residual in there.
Good info man I really appreciate it.
There is no problem putting oil in via bleed hole. First compression and its evened out.
3 ways.
1. Slowest, just push oil with a syringe with needle very slowly with wheels of the ground. Painful slow since oil travels slowly and air needs to go out
2. Compress fork slowly with bike on the ground, and when it rebounds you push oil in at same time. No needle. Just syringe. And preferably one that seals against the bleed hole. Might have to compress fork 2 times for 5ml. Don't push in to much at one time, you will hear and feel when it doesn't suck oil anymore.
3. Remove front wheel and do same as step 2. Easier to compress just one fork with one hand. Depends on your reach.
Pit Row
What's the max amount of oil one can put in the fork through the bleed hole? Are there any limitations or considerations?
I do not understand the problem with filling small amount of 10-15CC of oil from the bleed hole? sometimes oil is leaking when I am bleeding the air, I guess it's oil trapped, but still its lower the total of air volume.
I just tried today to fill 15CC, when the oil did not went down I used Hair Dryer to heat up the air in the fork.
I use the plastic syringes . They work very well I only add no more than 10ccs at a time though
This is the easiest best way to do it
there are two styles of compression assembly on KYB AOS forks. Both will tolerate adding oil through the bleeder port.
Late model compression assemblies are drilled straight through to the inner compression spring chamber above the free piston.
These later models (like @Crash82's 2023 YZ450F) have vented, self-bleeding free pistons.
When you add oil to theses later forks, it travels straight through from the bleed port through the inner compression cap and drops down into the top of the free piston. If you shine a flashlight down into the bleeder hole, you can see the spring and free piston down inside.
Since the later model KYB free pistons are all vented, that oil can drain out into the outer tubes.
Early KYB cartridges 2006 to about 2017 depending on make & model are drilled from the side so that the oil goes directly to the outer tubes. On those older 24mm cartridges, the bleeder does not connect to the sealed chamber above the free piston.
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