Spongy front brake

I had a similar problem with a Husqvarna 125. The brake simply would not get a hard feel despite lots of bleeding. It turns out the problem was one of the little springy anti-chatter/squeal clips that the pads rest on had gotten cock-eyed and was jammed between one piston and the caliper. It wasn't letting one of the pistons put any squeeze on the pad, so it took a lot more lever travel for the other piston to flex the pad into the rotor and give any braking power. I ended up just pitching the clip, and now the brake works great.

Of course, you've been in your caliper half a dozen times, now, so you probably don't actually have this problem.

Not a direct answer, but all of my Yamaha front brakes, while good, are not in the same league as my Hondas. Just this morn the big pig CRF230F's front brake had me super impressed when hopping off my YZ. It's the one slight downfall in an otherwise kickbutt package.

Just put a spare 04 master cylinder on the bike and voila had brakes!!!! Had to order another kit for my cylinder, brain fart on putting cylinder back together. Didn't use any special bleeding technique on old cylinder. Why?

Something amiss with your master cylinder you've been working with?? :eek::smirk:


I have an 08....had the same problem...replaced the line,replaced the master cylinder and finally rebuilt the caliber....it was super easy...make sure u put brake fluid on the seals....brake works great now......best way to bleed is keep cap off of master cylinder,make sure its full....duh....use a small rubber clear hose into a bottle with fluid in it ....sub merge hose in fluid and crack your blender bolt...now pump your lever until u get low on fluid but still enough.....now look at the little clear bubble n the bottom of your master.......if there is any bubbles stuck in the u have to move it around till they are all clear...can be tricky and make sure u keep enough fluid in but that's what finnnaly fixed mine...good luck.

I am waiting for another rebuild kit for my master cylinder. I have bleed this thing until I was sick of it. Have tried all of the tricks here on thumpertalk. It seems funny that a old master cylinder works better than the original. There is still air in the 09 cylinder. Will give it another try.

Lol yes I thought the same thing.....after I put the new brake line on I pumped for like 5 min straight n could never get a good feel....after the master cylinder( original when I bought the bike used was off a kawi,didn't know,it took me prob 10 solid min of pumping and bleeding to get a good feel on the lever....if u use the tube system and leave the blender valve open while u pump,making sure u have enough fluid it makes It alot easier.. as I said before check for the bubbles inside the clear bubble in the master....u will have to move the bars back in forth in such sometimes quickly without spilling fluid...lol it can be frustrating....just keep fluid and keep pumping and as long ad u know your components are solid it will get solid....last week after I Installed the caliber rebuild kit...I pumped for like 9-13 min solid to make sure....good luck. Switch hands often cas it will get tired.....good luck.

Got sick of master cylinder and bought a brand new one. Same problem. Have tried every trick to bleed it. Would the old master cylinder have a different bore size? Could the after market brake line be causing problems? What if the volume was more with the 04 cylinder than the 09 and the brake line was alittle larger? Any ideas?

even if the line was a larger diameter than the oem one, it wouldn't have an effect on volume. the same amount of fluid will be displaced when you squeeze the brake. Try something that worked for me, drain all of the fluid out of your line/caliper/master and do the whole process over. I'm betting you have a bubble somewhere.

The '08 and later YZ450 had a different master cylinder/caliper combo that the earlier models did. Hydraulic systems like brakes work on "leverage" rotios just like mechanical brakes do, but it's the ratio of the bore of the MC to the bore of the caliper that matters. If you used an '04 MC on the '09, you will probably have reduced the advantage the lever has over the caliper, which will require a harder squeeze, and contribute to a mushy feel because of the effort needed.

The size of the line is only a problem when it gets to be so small that it's restrictive, although a bigger line may feel mushier if the material it's made from flexes/bulges under pressure because larger diameter/longer lines have more square inch area of material to flex.

Another thing to check: Make sure your brake lever is adjusted correctly. I had the lock nut on the adjuster come loose on mine and the adjusting bolt slowly worked its way into the lever. I was ready to buy a SS line or oversize rotor until I realized the problem. Since the adjuster bolt moved in slowly, I didn't notice right away. Also, I agree with verifying rotor/caliper alignment, although if a different MC worked that is unlikely the cause of your problems.

The bike has a stainless steel line on it. The 04 mc feels great!!! I want my new 09 mc to feel like that. The 04 has great feel and alot of stopping power. I am having the local shop call yamaha tomorrow to see what they say. Will try draining the whole system and start over. Thanks for the advice, and will keep posting until it is right.

Hmm.. been back reading. Had all the complaints you guys have. What I did with mine was took off the pads, burned it on top of a stove for 10 minutes. You can clearly see dried contaminants on top of the burnt pads. With an emerald cloth, sand the face of the pad on a flat even surface. Bead accordingly using appropriate methods. That should do the trick even if the pads got soaked with FORK OIL. Did all on my road bike, dirt and even on my mountain bike.

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