Spongy YZ250 front brake

kremm140

kremm140

PR Member
Second question (new thread), I have bled and bled the front brake on my bike and it still feels spongy. I've already installed a braided line. I ran across a couple of threads that indicated the master cylinders are a problem on the YZ and that people were having luck switching to Honda cylinders. Some said you can rebuild the YZ cylinder with Honda parts. Does anyone have any thoughts on this?
Jay
 
they are both nissin brake masters, parts may interchange. brake lines mount differently to the master cylinders though may need a honda line.
 
Thanks, Yeah it sounds like there's something slightly different about the Honda piston that gives the brake a more positive feel. I couldn't tell by what I was reading if just a Honda rebuild kit would work, of if I needed the whole master cylinder (and would my line work with the Honda cylinder)
 
Just a thought here...

What made you bleed the line? Was it spongy before you bleed it?

My experience with brakes is that it is difficult to push air bubbles down hill with the small stoke of a brake cylinders piston. Once you have used a vacuum style bleeder you will never go back to bleeding brakes by hand. Even when you think all the air is removed...when you use a vacuum unit there are still small air bubbles that come out. Just make sure the master cylinder stays full and things are much better.

Just my 2cents
 
Thanks, I agree, its hard to bleed properly without a vacuum bleeder. My first move was actually the SS line. After not getting the better results, I did tried bleeding every way I could think of. Started with a vacuum bleeder, tried the lever pulled in overnight trick and then even tried vacuum bleeding with the caliper elevated (to move the bubbles uphill). I never really thought much about the condition of my master cylinder until a couple of days ago, and that's really the last thing I can think of to look at. Maybe I'm just being too picky, the brake certainly works, but instead of feeling firm, if I squeeze hard enough I can get the lever to almost pull into the grip.
 
take a zip tie, pull front brake all the way in ,zip tie it to the handle bar, full brake over night, cut zip tie off
 
ironman said:
take a zip tie, pull front brake all the way in ,zip tie it to the handle bar, full brake over night, cut zip tie off
Click to expand...

Explain to me how that helps eliminate air in a closed system or helps the lever feel more firm/less spongy.
 
Ironman's right (being the wily old veteran that he is). By zip tying the lever, you create line pressure that shrinks the air bubbles and makes it easier for them to rise and naturally escape out the top of the master cylinder (actually, if you never bleed your brake, eventually the bubbles should rise to the top of the master cylinder). This works well most times, but occasionally the air still won't travel up just by gravity alone.
 
I've had a front line be contrary to the point that a vacuum wouldn't get it working right. What's worked the best for me is using a large medical syringe to force oil up from the bleeder valve to the oil reservoir at the top, as the top reservoir starts to over flow I draw some out and keep pumping it up through the line for a bit.

Good place to find a syringe? Our vet gave me a couple of large syringes used for large animals.
 
I work on Honda's and had a customer with this problem. I even rebuilt the master but the lever still just didn't feel right. The problem wound up being the tiny adjustment screw on the lever itself had worn causing excesive clearence at the actuation point. New lever, adjusted screw most of the way in, and brakes felt great. I could not get the lever to the bar no matter how hard I tried. I have checked this on a couple of other bikes and that screw is almost always worn and a new screw/laver makes the brakes feel great.
 
mooch said:
I've had a front line be contrary to the point that a vacuum wouldn't get it working right. What's worked the best for me is using a large medical syringe to force oil up from the bleeder valve to the oil reservoir at the top, as the top reservoir starts to over flow I draw some out and keep pumping it up through the line for a bit.

Good place to find a syringe? Our vet gave me a couple of large syringes used for large animals.
Click to expand...
Tractor supply has big syringes for horses and animals.
 
mxsk8r007 said:
I work on Honda's and had a customer with this problem. I even rebuilt the master but the lever still just didn't feel right. The problem wound up being the tiny adjustment screw on the lever itself had worn causing excesive clearence at the actuation point. New lever, adjusted screw most of the way in, and brakes felt great. I could not get the lever to the bar no matter how hard I tried. I have checked this on a couple of other bikes and that screw is almost always worn and a new screw/laver makes the brakes feel great.
Click to expand...

I put a ASV brake lever on my sons Yamaha YZ85 and the brake felt spongy. I tried bleeding the brake but it still felt spongy. So I decided to put the stock lever back on and it felt great. Put the ASV lever back on and it felt spongy. He wanted the ASV lever, so that's what he riding with.
 
Original44 said:
I put a ASV brake lever on my sons Yamaha YZ85 and the brake felt spongy. I tried bleeding the brake but it still felt spongy. So I decided to put the stock lever back on and it felt great. Put the ASV lever back on and it felt spongy. He wanted the ASV lever, so that's what he riding with.
Click to expand...
The leverage ratio is different between the levers.
 
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