08 front brake help

[stlyamadude]

PLEASE PLEASE HELP ME FIX!!!!! ok got the bike used...front brake didnt work great...fork seals were leaking so figured maybe the pads wee oil soaked..fixed seals and put on new pads...didnt help.....talked to the guys at the local shop...told him my front brake does not work great..i have a solid lever but thats with the lever adjusted all the way forward and when pulled about with in half inch from handlebar...ive bled them twice untill always feels good sitting on a stand in the garage but once out it works but....put it like this...i cant lock up the front tire...i can if i use all 4 fingers but still kinda hard....so guy says o ya u just need a stainless braided line...ok put that on...yep waste of 65$..lol kinda knew that wasnt the prob but was gana get one anyway..lol.....so rode it bled it rode it bled.....still the same....bought a rebiuld kit for master cylinder...didnt fit...come to find out it was not a yamaha master....sooooo got brand new oem master and lever oem and installed...gata say i was thinking finnally its fixed....NOPE.....got a rebiuld for the caliper...did that and bled 4-6 times over the next 2 months...still the same...lever is solid but with a lot of lever play...the master does not leak....caliper does not leak....line does not leak....i have bled the system about 12-15 times and have always got all the air out and come out with a good feeling lever when in my garage..but out in the woods it just ..........will say 65-70% works.....so what is wrong with it???? every time i bleed it i always go like 4 more pumps/bleeds past the last air i get...i have sanded my rotor...ive changed rotors...ive changed the brake lever once...read a post about the bore hole in some of the levers not being deep enough and cause the brake to drag..thats not it...i have changed back to my factory line and back to the stainless.....caliper floats fine......pads still good....i mean look.......i have a new lever..new master cylinder..new brake line...new banjo bolts....new pads....new caliper rebiuld kit...what else is there short of a brand new rotor and a brand new caliper....and i am going to buy a new caliper soon if i cant fix it...lol.....the only thing i can think of is that there is air that is some how getting trapped in the caliper and for some reason wont bleedout...like there is a pocket inside the back of the pistons or somthing...idk...please help....2008 yz450f....

[grayracer513]

There's a lot to sort out there. If I read it right, you're still using an '08 master cylinder and caliper, right? One of the complaints people have about the YZ450 in general is that they don't think the brake is strong enough, so it's probably not anything "wrong" with yours that you can correct by "fixing" what you have.

Let's look at one aspect of what you said, though: The free travel in your front brake lever comes from the master cylinder and lever assembly. Part of that is obvious and visible from outside, and part of it isn't. There should be very little clearance between the lever and the end of the MC piston that the lever bears against. It only needs to be true to begin with that the lever is not partially depressing the piston when at rest.

Internally, there is a certain amount of play built in. You know there's a port in the bottom of the fluid bowl on the MC where the fluid flows from the bowl to the actuating cylinder and line. This port also allows heated fluid to expand back up into the bowl and return when things cool off. At rest, the piston has to return far enough for this port to open. As you apply the brake, the piston can't create any pressure in the line until it crosses over the fill port and into the closed bore, so that much of the travel is "free play". The piston only needs to come back far enough to completely open the port, and if it goes farther, there will be more play than needed. If you try to adjust this out, you need to be careful that you do not close it off or the brake will lock as it heats up. To test, push the pads back and watch for fluid coming up from the port (watch your eyes).

If you can find a set of Honda CRF brake pads that match up to yours, try them as a cheap upgrade. This was a quick fix for the '07 and earlier models, but I don't know for sure on the later ones with the new caliper. On the earlier bikes, another popular mod was to use an '04-'06 CRF master cyl, but again, with the brake update, I don't think that one will work. Probably the surest thing to do would be an oversized rotor kit. That will make a significant difference.

[stlyamadude]

i will visually check for the return of fluid as u explained..thank you...i have always heard that the yamis front brake was much to be desired...specially before the cr routing of the line...so anyway...i have riden my buddies 07 and his is say 15% better than mine so will say his is 85%....and have also riden another buddies 09 and his is def 100%!!! what is the diff between the the 3 years??? or r there any?? as i said i bought mine used and found that it did not have a 08 yamaha mc....i thought and still think that it is off a honda...i tried to look up part numbers i couldnt figure out and my local bike shop couldnt help me..lol they are great here n st.louis...lol.....:{....so ...how do i find crf pads that will fit without buying a few and finding the one that fits??? any thoughts on that one?? and yes my next step after buying a new caliper was going to be go to a oversized front rotor set up....pretty pricey tho...my thought was tho that if the 07 and 09 i rode have front brakes that would satisfy me then why not try n fix mine...alough that has proved to be harder done than said...ha ha ha i know duh....caliper is around 200$ and oversized rotor kit is 260$+....so its cheaper to do the caliper...but thats only if it fixes my problem...obviously...so i could be in for a caliper plus the rotor kit on top....could be at 500$ real quick....what about if the guy before me had changed the caliper with the mc at the same time...if they weremix matched would or could this be my problem??? and how do i figure out if this is the case??my current caliper fits perfect ....are there part # ican look for and cross reference??? i ambegining to think that maybe my best bet would be to go with the oversized rotor kit becuase i would probly get the most performance out of it...yes??

[stlyamadude]

o and sorry yes i am currently running an 08 master...also...i little more info on lever feel.....normal lever feel would be say 1 inch...like pulled in 1 inch qould be full front brake lock up.....maybe a little more but just for arguement sake...so mine is say the same but at the 1 inch mark it is just starting to grab...ok and normal front brake lever feel is, will say like a wall..once u hit the 1 inch mark u really cant pull it anymore...so back to mine....my wall is at 1/4-1/2 from the bar...and thats with all fingers...so as i said inthe beg i almost cant get my front brake to lock up...using one finger it is pretty much not happening...not that i want it to lock up of course but knowing that its availible is what a guy wants... hope this helps out with understanding my problem a little better...am still thinking that the oversized rotor is the way to go...still think somthing is wrong with my set up tho.......?????

[grayracer513]

The two things that commonly cause a soft or spongy feel in the brake lever (assuming no air) are the pads themselves, or the caliper not sitting square with the rotor. Watch the caliper while you squeeze the lever. If it twists or rolls or moves much at all in any way when pressurized, try to figure out how to adjust its position so it sits more perfectly aligned with the rotor.

If you can find a busy shop that carries the pads in stock, you should be able to compare yours to them on the counter. Even a fresh pair of YZ pads may be enough.

Don't be too hard on the parts guys, though. The numbers on the part or assembly itself doesn't always tell you that much, and it can be tough to figure out that way.

[stlyamadude]

maybe i willtry some new pads..they are fairly inexpensive......worth a shot....i have had that thought about the caliper being square with rotor...becuse yes i have noticed that my rotor does move slightly when i depress the caliper...i have a solid galfer wave rotor that i usually run and i cant really notice the rotor move...i did change back to stock wich is the free floating rotor,and since i can see the rotor move...of course thats kinda the point of it tho...i am not sure how the caliper could not be square because it is also free floating an it should me itself sit where it needs to be...what doesnt make since to me is that if my caliper is bad, y doent i leak??like maybe the cylinders r warpped or uneven so to say...but if that were the case then y dont it leak rite.....??? wait....im a dummy...the pistons slide in and out of the bushings and seals...this problem wouldnt have anything to do with this...the caliper is just a housing that holds fluid and when fluid is pressuered into it,it moves the pistons out because the pressure has to be released....ok sooooooooo...i have checked to make sure the caliper does float and it does...i wonder what the chances r of getting a defective master??? if it was bad tho it should bleed off all the way...hell idk.....and as far as the part numbers go...ya i was affraid of that...well i will continue to try in sort through it...trial and error....