Brakes went soft after sitting for a few months

I have done a search and found similar posts, but nothing quite answers my question...

My 2010 FE450 brakes worked fine for the first 1.5 years. They worked fine in April. My bike then sat in the garage until July 4th. I then noticed that my front brake level pulled all the way in to the bar. I also noticed that my rear brake did essentially the same thing. Neither brake offered any stopping power. I tried pumping the brakes, with no change.

I then did a search and found people with similar problems, but I didn't like most of the responses given. Most people suggested the brake fluid had gone bad. I don't buy that theory. Even if it is "bad" or contaminated, it wouldn't suddenly become compressible. That just doesn't make sense.

Others suggested air in the line - but I don't buy that theory either. The symptoms are wrong. If I had air in the line I would expect pumping the brake to help, and I would expect the brakes to work, but then fade.

Oh, and there is not a leak - the reservoir was full to the brim.

CrazyTed posted a suggestion of tying the brake lever to the bar and letting it sit. So I tried it. I let it sit for about 1 hour while I went to the store to buy new fluid. When I got back, my front brake worked! It felt tight and it had stopping power. So, I tied it off and let it sit overnight. I wedged a board in place to hold the rear brake pedal down and let it sit.

After doing this magic overnight treatment, my brakes worked perfectly!

So, what I am now looking for is the explanation behind this.

Here is the best theory I have come up with...

With the brakes sitting unused, the master cylinder piston seals dry out. When I pull on the brake, the fluid leaks past the dry seals and I don't get any pressure. By 'parking' the piston in the 'brake on' position, it immerses the seal in fluid, which causes it to expand and once again work.

Is that theory valid?

If so, should the seals be replaced? Or will they be okay now that they are wet again?

If not, are there other theories?

Haven't a clue about the theory but my front brake does the same if not used for a while. I solved the problem by leaving the bars turned to the left so the front brake lever is the highest part of the system. I've also had success by pulling the front brake lever in and then let it go/allow it to flick forward half a dozen times.
KTM's are renowned for doing it too so must be a brembo problem. Never had it on nissins etc.

OK DeeG, first things first. Why in the heck did the bike sit unridden for 3-4 months? That's just wrong!

I've had to do the front brake thing on KTM's for years, never had to with the rear though. Folks claim by securing the lever, it forces any air in the system to the top. But being a sealed system, where does the air go if you don't bleed it :?: Like you I can go from no brake to stoppies by zip tying the lever overnight.

It appears KTM might realize there is an issue that can be solved by doing this
http://www.calmoto.com/SHOP/KTM/61012016000.html

mikecarpenter said:

OK DeeG, first things first. Why in the heck did the bike sit unridden for 3-4 months? That's just wrong!

I've had to do the front brake thing on KTM's for years, never had to with the rear though. Folks claim by securing the lever, it forces any air in the system to the top. But being a sealed system, where does the air go if you don't bleed it :?: Like you I can go from no brake to stoppies by zip tying the lever overnight.

It appears KTM might realize there is an issue that can be solved by doing this
http://www.calmoto.com/SHOP/KTM/61012016000.html

Click to expand...

I agree that having the bike sit is just plain wrong - it has been a very busy spring. I was about to remedy that with a 3-day trip last weekend, followed by several more outings. Unfortunately, my son broke his arm on day three, so that may set us back for several weeks.

Interesting KTM lever holder. Obviously, this is a common problem. But I guess I won't worry about replacing any parts or fluid.

I have an FE390 and just discovered the same prob. Haven't ridden it for 2 months: almost no front brake. Reservoir full. Handlebars sat straight forward. Have tied a zap strap around the front brake lever. Will update with my findings.

I had this happen on my KTM Brembo system.

I found that a little air was in the system. The brakes worked fine when used regularly but when it sat the air shifted and to the top it went causing the soft lever. Then pump it up and it was fine for a while.

Bleed the brake system completely and your off and running. Could have got a blurp of air from a fall ect.

Hope this helps

I had good front brake on my 570 until I slammed it hard in a crash. I guess some air came into the wrong place as it's been soft ever since. I have tried to bleed and fill using most methods, even replace the piston and rubber. It's better when I have it zip-tied and at a high position over night, and it is alright most of the time but not as good as new. I just tell myself I have a poor mans ABS....

jon andersson said:

I had good front brake on my 570 until I slammed it hard in a crash. I guess some air came into the wrong place as it's been soft ever since. I have tried to bleed and fill using most methods, even replace the piston and rubber. It's better when I have it zip-tied and at a high position over night, and it is alright most of the time but not as good as new. I just tell myself I have a poor mans ABS....

Click to expand...

I've been using the overnight zip-tie method on spongy Brembos since the '90s. Always works works like a charm. Well except when I had a damaged caliper on my old ATK 605.

Well, the zip tie on the brake lever for several hours worked a treat. A few pumps after cutting the tie and she's rock hard. Going to bleed the system, service the calipers, and replace the pads today anyway and see if the crash-air in the system theory has any credence. With a 100 hrs since new, I doubt this has been done (I got her at 50 hours). She sat for 3 months over winter last year, and I don't remember this happening.

Ktm 450 sxf brake issue

Deeg,
thanks for the tip on pulling the brake handle in and leaving it in that position for an hour or so....it worked on my bike also.
Mitjo

Works for me too. I use a velcro strap.

Also put the bike on a battery tender since pulling the brake lever turns the brake light on.