Hydraulic hand lever with sight glass brake bleeding issues

Abtheman28

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Hi guys,

Has anyone out there ever bled one of these systems before? It's a hydraulic hand lever to a single rear caliper assembly.

I have just replaced the hand lever and hose assembly to my existing brake caliper with a new one. The issue I'm having is I'm unable to get any hydraulic pressure to the caliper after bleeding the system the normal way .... open bleed nipple then pressing hand lever in till fluid comes out nipple then tightening up nipple again. However I have managed to get flyod through to the caliper and bled lots of fluid out..... however the little round sightglass as seen in pic attached just below reservoir I cannot seem to get rid of an airlock which I can see through the glass window which obviously must be the issue.

Has anyone had similar issues with this setup and what is a way to eliminate the air in the little window? It doesn't seem to matter how many times I fill the reservoir and bleed the normal way... it still won't clear the air in the little window on hand lever assembly.

I have seen videos of guys reverse bleeding brake systems on different setups but unsure if this is the right way.
 

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madprofessor

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Yep, know exactly what you're talking about. That bubble will always exist until you turn the MC vertical and pump it out. Unfortunately, your so-called reservoir isn't big enough to help as long as the MC is horizontal. Mine was even worse, here's a fairly close approximation of what I started out with for $21 back then...............ATV Go Kart Rear Hydraulic Master Cylinder Brake Disc Calliper Assembly | eBay................
plus a 86" hose I started with to replace the 18" the assembly came with................86" STAINLESS BRAIDED HYDRAULIC BRAKE HOSE LINE SCOOTER ATV DIRT BIKE GO KART | eBay.................. Then here's how I fixed the situation (note that it's the exact same MC except for reservoir)................
Rear Hydraulic Brake Master Cylinder Go Kart Sport Sprint Cart Kit Bike Chopper | eBay..................Voila! Problem solved, even with 86" hose. Reservoir is good for about 20 pumps with that MC. NOTE: Your air bleeder should be at the top of the caliper when mounted!
Open bleeder, press and hold, close bleeder. Release and repeat, 2peat, 3peat, 4peat,.....................................................................etc.
 

Abtheman28

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Thanks mate. Yea I've hunted all over Google and YouTube for anyone globally who may have had the same issue as me and pretty much zero luck apart from a YouTube video I found with a guy talking about the tiny inbuilt master cylinders on minibikes and how to eliminate air locks in them. He also mentioned being the fact that each individual pump of the hand lever only moves such a tinnnnyyy amount of fluid it's basically impossible to get rid of air locks.

He carried on talking about and showing a reverse bleed from the caliper right back up through the full system to push the air bubbles out of MC so tomorrow I'll give that a try and fingers crossed because I'm lost for ideas if this fails and surely from factory they must have a way of bleeding the air out ...

Yup my bleed nipple on caliper is at the top and my MC is vertical directly above the sight glass. Just unsure of flow through master cylinder. I'm hoping when I push the fluid backwards itl go through sight glass before it end up in reservoir. If that's the case I'll be happy! No more air lock...
 

Abtheman28

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When you mention that the air will also stay in that sightglass until you pump it out....how exactly would do I this? My MC is vertical and has to be as that's the way it's mounted. When I did a normal brake bleed it did nothing more than half fill the glass and no more liquid would fill it to 100%. Any answers be great! Mean while I'll do the reverse bleed
 

Karttekk

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What worked for me when bleeding a system with a brake pedal instead of a brake handle was submerging a section of hose in a partially filled bottle of brake fluid with the other end firmly secured on the bleeder. Top off the master, open the bleeder then squeeze the handle repeatedly watching for bubbles in the partially filled bottle while keeping the master topped off. Once no more bubbles appear in the bottle tighten the bleeder and top of the master. See if that works for you.
 

madprofessor

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my MC is vertical directly above the sight glass.
Not sure what you're saying about vertical. What I meant about vertical was the MC having its plunger end down, and the hose end up. And it takes more than 2-3 pumps to get things going good. Having to stop, invert it, refill, and start again ain't makin' it. That's why I got the "reservoir-on-a-tube" type MC to replace the old POS.
Open bleeder, press and hold, close bleeder. Release and repeat,
That's just the classic old phrase for most automobiles, gokarts are actually something else. After my 2-3 pumps frustration, when the MC with the reservoir came in, I just attached the 86" hose to it, laid the hose on the floor, and pumped like a madman (MC mounted on the kart in its regular horizontal position, reservoir up above it) until it quit spluttering air out. Attached the open end to the caliper, then practiced what I preached above to bleed the caliper itself. Have solid brakes now, and I'm done complaining about it.
 

Karttekk

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When I bled the system on the kart I mentioned, it only took maybe 10 pumps if that. Definitely worth a shot. Try a clean, clear plastic bottle in order to see any bubbles easier.
 

Abtheman28

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Thanks for your help. I ended up removing the full assembly... MC and caliper mounted the caliper higher than reservoir attached clear tube to bleed nipple and other end of tube Into brake fluid and just pumped Like a mad man. Tried tapping on brake hose between caliper and reservoir and after what felt Luke 500 pumps later and constantly filling the pissy asses reservoir I finally got a gush of air bubbles come through and soon after managed to achieve a good solid brake lever :) 😀
 

madprofessor

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If only one thing gets learned by everybody reading this thread, let it be this: DON'T EVER get an MC without a good capacity, easy access reservoir for multiple continuous nonstop pumps without having to stop for a refill.
Easy access means when permanently mounted that it can readily be opened and a bottle of fluid poured into it. My replacement one with the reservoir on a tube is the easiest access of all, as it can be mounted anywhere at any angle regardless of the MC mounting.
 
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