Juin Tech/Yokozuna bleed? Mine are locking up under heat

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jockstick
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Joined: Wed Nov 14, 2018 2:20 am

by jockstick

Has anyone bled these? If so, how did you do it? Did it improve your braking?

My Juin tech GT (4 pistons) are locking up under heavy braking. I wonder if air or moisture has gotten into the body causing expansion under heat.

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ms6073
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by ms6073

There is the Juin Tech R1/F1 bleed thread that asks the same question but no ansewrs and only a link to Juin Tech's Facebook page. Since it is a closed system and given the relatively low costs, my guess is that replacement is easier than bleeding. Finally, there is a thread on singletrackworld.com in which the question is asked about a Juin Tech calipers in which someone does offer a brief desciption of how to bleed the caliper in question.
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jockstick
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by jockstick

Thanks, I'd come across all of those already so far. Was hoping there'd be someone here that's done it and hasn't written about it.

Or even if anyone's done it and can comment on if it's even worth doing, that'd be great to know too

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wheelsONfire
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by wheelsONfire

jockstick wrote:
Fri Aug 06, 2021 4:33 am
Has anyone bled these? If so, how did you do it? Did it improve your braking?

My Juin tech GT (4 pistons) are locking up under heavy braking. I wonder if air or moisture has gotten into the body causing expansion under heat.
Don't they have a service request email or pdf or even video clip of this procedure?
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dlj2119
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by dlj2119

I have opened them to squeeze out a little oil so that the pads would be wider appart, but have not done a full bleed. Letting out a little oil was very straightforward.
My own research has not turned up any service documents from the company. The most information came from the re-branded Yokozuna company, but they say they shouldn't need to be bled. Wondering if you can contact them to see if they have any experience.
https://www.yokozunausa.com/downloads-instructions-yoko

CyclingGiraffe
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by CyclingGiraffe

Anyone have any luck on this or adding oil? Like an idiot, I tried letting a little oil out to give me more clearance, and I think I let too much out and will have to add some oil.

CyclingGiraffe
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by CyclingGiraffe

So, following up my post above -- where I let out too much oil and possibly let in some air -- I did add oil and bleed my Juin Tech GT brakes the other day.

I followed the process in the video for the TRP Hy/Rd calipers I found on YouTube, using two syringes and removing the caliper from the forks for ease of use and the pads from the caliper to avoid contamination. I used Finish Line mineral oil, which, coincidentally, is the same greenish color as the oil that came stock in the Juin Tech calipers. The ports are pretty much the same as the M5 port used in 1/2 of the Shimano bleed kit. The one problem I had is that both bleed ports on the Juin Tech GT calipers apparently are shallower than the standard Shimano port and so the fitting bottomed out before contacting the o-ring seal. I just tightened by hand as much as possible and had some, but fairly minimal, leaking, even when compressing the piston (with a brake block/spacer in place, of course!) to make sure all air bubbles were worked out.

In the end, my refill and bleed seems to have been successful. The piston is much firmer again, like how it was delivered. There does not seem to be any leakage at the bleed ports, though I will keep an eye on them. Clearance is still very tight, though, with new stock pads and Shimano XT discs (which is the issue that led me to crack them open in the first place to let out a "bit" of oil). Of course, ymmv, and anyone undertaking this procedure does so at their own risk and apparently voids the warranty as well.

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sethjs
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by sethjs

Has anyone had an issue w the Yokozunas where the first pull on the brakes after awhile doesn't produce enough clamping force at the disc? That is, similar to a full hydraulic system that's in need of a bleed?

I'd not have thought caliper-only hydraulic systems would behave like that, but I've noticed this a few times seemingly at random with the Yokozunas. First squeeze after sitting a bit isn't super powerful, but then they get better.

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