Thanks mjn, I did those steps last night. I bled the system until I got fluid out of the bleed valve, then let it sit overnight with the brake lever tied. This morning I got the lever semi firm, but not hard jaja. At first there were air bubbles coming out into the master cyinder and also from the bleed valve, but then just clear fluid from the valve and no more air bubbles in the MC, I even tried tapping on the hose and caliper while I bled for 15 minutes but still the lever is not hard. I test drove it slowly and it's now braking softer than before. This happened last time I bled the system until I left it overnight a couple of times. Any ideas?

 

Ok, a few more hours of having the lever tied and the brakes are now as they were before. After a few test brakes I performed a final bleed, the fluid is clear and couldnt see any bubbles until I looked very closely at the clear tube, I could see a string of very very tiny bubbles, smaller than a pen tip. Is this normal? Im using lucas synthetic dot 4 fluid, its always been sealed in the MC, and most of it is new from this bleed. I guess as long as the bike is braking as it should, then I shouldnt worry.

Thanks to everyone who replied to the thread, couldnt of done it without your help. The caliper is now cleaned and looks to be in real good shape.

Cheers

 

Honestly to anyone who does their own brake work, get a vacuum bleeder. They work better than any other method. Gently suck the fluid through the system vacuuming out the air as you do it. You will not regret it after your first bleed job. I bled the rear brake on my Zephyr after a caliper rebuild. Bleeding took all of about 2 minutes from putting fluid in the reservoir to putting the lid on it after bleeding.

If one had a large syringe and could fit up a hose of the right size, the same could be accomplished. I think I've read about some guys using a turkey baster, but can't say for sure. It takes such gentle vacuum that I could believe it. Saves on zip ties too.

 

Totally off the OP subject, but following part of the train of thought here... and a bit how my brain works - aka I want to at least understand the foundation behind what appears to be bizarre claims.

The problems had with braking going soft or the like brought up the rather bizarre zip-tie around the brake lever with what seemed to be magical qualities.

Some research I did along with comments from the Thumper Talk forum brought out a few questions. Why would pressurizing the system make the brake firmer and how?

I found a few articles on air in hydraulic systems and learned the following:

Air can be present in four forms:
• Free air - such as a pocket of air trapped in part of a system.
• Dissolved air - hydraulic fluid contains between 6 and 12 percent by volume of dissolved air.
• Entrained air - air bubbles typically less than 1 mm in diameter dispersed in the fluid.
• Foam - air bubbles typically greater than 1 mm in diameter that congregate on the surface of the fluid.

Of these four forms, entrained air is the most problematic. Pre-filling components and proper bleeding of the hydraulic system during start-up will usually eliminate free air.


So, filling a brake system and bleeding will get rid of free air, but the dissolved and entrained air will be a problem. Some dissolved air will percolate to the top and bleed out through the reservoir port if that is the high point off the brake system. But the entrained air and some of the remaining dissolved air may become an issue.

In another article, "How Hydraulic Fluids Generate Air", it was pointed out that the entrapped and dissolved air can settle out of hydraulic fluids through use. Sometimes it is reabsorbed, sometimes not. I cannot pretend to have entirely read and understood everything written in this or several other articles I read, but I can say it presents a very good argument for why the zip-tie thing could work, with pressure on the system possibly freeing up the entrapped and dissolved air into larger free air that can either percolate out off the system into the reservoir when the lever is released (sometimes causing an increased back pressure that could spray out of the reservoir as one post in the Thumper Page forum described.) or bled out. It also makes conditions for why brakes may go soft at times.

Here is a short quote from the article:

Because air in solution in a hydraulic fluid has only a minor effect on hydraulic performance, why should the designers be concerned with it? The answer is that even if all the air bubbles and pockets were removed from a hydraulic system totally enclosed, after a short run-in period, air bubbles would begin to reappear.

The source of these bubbles is the working fluid itself because all fluids (except fully deaerated ones) contain dissolved air that, under certain conditions, comes out of solution and plagues the system.


They also made mention of three of the four forms of air in a hydraulic system and there was an interesting point in there about vacuum effect

(I think there was a typo on the part about entrapped air that is released not affecting volume, it would affect volume.)

I'm thinking there is light vacuum whenever the lever is released and the pressure on the system is released. It also may point to a benefit of using a vacuum bleeder too. Although that may or may not be true. Regardless, the article definitely gives rise to reasons why some semi-mysterious things occur with brake (hydraulic) systems.

At this point I'd say read the article if you wish. I now have some limited understanding and can see possibilities why the zip-tie thing may work. I also gained some insight into air in a hydraulic system and the possible methods to either remove it or have it release to the reservoir on its own.

As you see, sometimes I just can't "take it for granted" when questionable solutions are proposed. Kind of like how magnets on your gas line will increase mpg or that turbulence inducing product stuck up a few feet from your engine's intake port will give higher horsepower and mpg again. Just because people may say it or manufacturers may claim it does not make it so. If that was true, mini-vans would actually be, as the advertising claims, sporty and that punk kid's old 600 supersport would, as the squid claims, 170 mph with half throttle to go!

Oh, and by the way, you might consider being careful with your brake fluid container before you pour it in. It could be worth letting it sit for a day just to let any free air combine at the top, then be careful not to stir it up while using it. Or not, can't guarantee it would make any difference. Heck if you shake it up you're possibly creating dissolved and/or entrained air in the fluid.

 

klx678, I am definitely getting one of those for next time. This has been a pain but worse it takes a couple of days to get it fully bled. Yesterday morning the MC was 3/4 empty after topping off the night before and the brake was a little softer than the day before. Last night I left the lever tied again and today the brakes are back to normal. So in all 3 days and 4 nights to get this bled manually.

 

Lot more than 5 minutes!

I guarantee you if you do a vacuum bleeder and keep the vacuum draw low so as to not draw air in around seals or by draining the reservoir too fast, you will spend less than 5 minutes doing the job.

 

So its doing it again. It only started 2 days after the last time I "fixed" them but I hadnt been able to post. Same exact symptoms, soft brake lever, if I squeeze hard it locks up until dead stop then I can keep going.

Could it be a return line in the MC that is clogged or some other MC issue? Should I try using liquid teflon or some other sealer around the washers? Should I look at the calipers/pistons again? Could it be an issue with the hoses? They look fine.

I really appreciate any ideas for this as this is my daily transport to work and I cannot go on like this.

 

It seems it was being caused by a kink. The brake hose was being lifted up against the clutch cable and headlight switch harness causing it to kink. But, does this also explain the soft lever?

 

The hose probably has internal damage. The hose is bulging instead of putting all the effort to the pads. Replace it with a braided stainless from Galfer or Bill Blue

 

This makes sense. And you will get new o-rings IIRC. I wouldn't use teflon. If there is a sealing issue, fix it correctly. You should see fluid leaking out if there was a sealing problem. A new SS braided line is a good thing. I've noticed a positive difference with them on the KLX and KLR.