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DirtriderZ
eagle

Brake fluid test Volts/Ohms

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I've been trying to bleed my clutch & it just won't  play ball, in the end i googled & found that these  tests tell if fluid is contaminated, & mine has failed these tests so it looks like i will have to flush out the system with some cleaner : ( . I'm wondering if anyone else has had this happen, i've changed the brake fluid in the KTM about twice in 18yrs, i had some issues with my Sherco's rear brake fluid & i'm wondering if Sherco uses cheap fluid ?

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Thinking too much mate!!!! Contaminated fluid is conductive so you can use a multi but you need to know the volts to determine how much mositure is in the fluid which is what those brake fluid tester are.

Reverse bleed the clutch is the best way l've ever got the best pressure outta a brembo system (both road and dirt), and tap the master cylinder and resi to dislodge any trapped bubbles during the process.

Brakes (rear), l push the piston all the way in, empty the master cylinder and reverse bleed as well. Once the fluid is all clean then l do the std method to bring up the pressure.

I do the same for the front but since finicky KTM brembo's circa 2012/13 onwards, after doing the same as above, l ziptie the lever to bar when storing to insure the system is pressurised and any trapped air bubbles are forced up to the resi....l've bleed a front and then overnight lost pressure!!

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Do what I did on my KTM. Should work on the other premier Euro bikes as well. Bought and fitted the genuine factory bling caps and levers for both the front brake and clutch, gave the bike a good clean and detail, lots of armour all and tyre shine, parked it in the garage and went for a ride on the Suzuki.

Seriously though, can it really be moisture in the fluid? It's very rare and usually needs to have had a bad cap seal and water ingress like from a pressure washer (much more than just moisture build up on the bike or in a plastic brake fluid bottle if its been left in the rain for a long time). If it gets water in it it'll still work (it'll work even if you run water as the fluid in it) but the clutch will fade if it gets hot and the water / fluid boils. What's it actually doing? If it drags I'd be measuring your clutch pack. I'm curious to see how you go.

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It's not a clutch problem as such, it had been sitting for a while & then it had NO feeling in the lever, i started to bleed it but it just seems like it has a lot of air in the line so i think i will empty the whole line & start again ?

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20 minutes ago, eagle said:

It's not a clutch problem as such, it had been sitting for a while & then it had NO feeling in the lever, i started to bleed it but it just seems like it has a lot of air in the line so i think i will empty the whole line & start again ?

Yeah, a flush never hurts. The clutch master cylinders do self bleed compared to brake master cylinders so an old fashioned flush should be OK if you don't have something to do the backward flush. Keep an eye on topping up the master as you go, only takes a couple of pumps to uncover the port holes. When you pop the cover off might as well do a few quick taps on the lever and see if any air bubbles pop out. If none comes out I wouldn't think there was a lot of air in the line.

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The best way is to use a large syringe and clear plastic tube. Put some new brake fluid in the syringe and push through the tube so no air. Put tube on bleed nipple. With your third hand before you Crack nipple pull some suction on the syringe then suction out a little fluid before tightening up the nipple.  Then let any air rise  until it goes in the syringe.  Once there is no air then you can push fluid into the caliper by first putting a little pressure on syrynge then cracking the nipple.  Don't release pressure without tightening nipple. Oh yeah you need to take off resevoir cap and put some rags around.  Stop when coming out clear. Brake fluid will absorb moisture over time how I don't know but it does even closed system.  A tip is to remove master cylinder and hook it so break line is vertical with no bends, and have some one tap the line as pushing fluid through. Works almost everytime. If pushing doesn't work sometimes suckling it back dislodges that one small bubble. Happy days.

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4 minutes ago, RickyD said:

Brake fluid will absorb moisture over time how I don't know but it does even closed system.

Brake fluid originally wasn't a mineral oil but a vegetable oil base and drew moisture by it's nature (ie hygroscopic. Mineral oils do as well but not as severely). Not sure what the fancy modern brake fluids are made of with all the synthetics and silicone fluids being marketed; I'm pretty sure the regular fluids are still vegetable base though. Condensation / moisture accumulates under the cap - the cap has small vent slits to prevent a vacuum; the rubber diaphragm moves up and down while your pumping the oil in and out to the clutch and your also pumping air in and out from the space between the diaphragm and cover. The rubber diaphragm whilst a good barrier doesn't stop gases being drawn through it over time including moisture (for example just like tyre tubes do).

The syringe approach is good but not necessarily better. Traditional method will get a bit more of the oil in the slave cylinder out.

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Yep, done it all ways. It just takes the dodgiest globules of moisture to boil up and release o2 then your buggered. Sometimes the old ways are better and worth trying, but brembos are a bitch 

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