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yz 250 front brake problems/ can you read this old piston

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M0102

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I bought a bike and it appears the front brake master cylinder is empty
IMG_2834_zpsk3ozr4fl.jpg


I started to try and get the screws off but I can feel them turning mush when I go to loosen them. Rather then completely strip them. does anyone have any ideas? the front brake is very squishy but it still works
 
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Re: yz 250 front brake problems

Get a syringe with a hose that will fit the bleeder screw on the caliper and then pump brake fluid up to that until it's full just make sure you don't cycle the lever while you have the bleeder screw open
 
Re: yz 250 front brake problems

Or get a screw impact driver. Very cheap at orielys or pretty much anywhere, the kind you hit with a hammer. A must have for all motorcycle screws.
 
Re: yz 250 front brake problems

Jeepman said:
Or get a screw impact driver. Very cheap at orielys or pretty much anywhere, the kind you hit with a hammer. A must have for all motorcycle screws.
Click to expand...

I'll pick one up tomorrow and give it a go
 
Re: yz 250 front brake problems

Ditto to the impact driver, but also you can just put the screwdriver into the screw and give it a few decent light strikes on the back with a hammer. For those little threads, sometimes that is all it takes to loosen them up.

Oh, and might I add; invest in good screwdrivers. You only really need 4 of them, so they might as well be good ones. I have seen more than a few screws stripped because a cheap screwdriver was used and it made a mess of things.
 
Re: yz 250 front brake problems

The trick is getting bit small enough for that screw. Keep in mind the driver should fit 3/8 sockets so you can install a 3/8 by 1/4 socket and drive any screw gun bits you might need to make it work.
 
Re: yz 250 front brake problems

The $11 impact driver worked :clap:

I found this piece of I guess foam inside
IMG_2835_zps6ubkzfir.jpg


Is this supposed to just be sitting in there? I can't seem to find anything online. I watched a couple guys rebuild master cylinders and when they take them apart I don't see it

It's little notches seem like it wants to belong somewhere but I can't find a way that turns a light bulb on in my head
 
Re: yz 250 front brake problems

I found someone saying its to control the fluid from moving around so I'll just toss it back in
 
Re: yz 250 front brake problems

IMG_2838_zps0yw2gd6w.jpg

IMG_2839_zpszctc56bp.jpg

IMG_2840_zpsrm5ota5y.jpg


Here's my old piston too. according to the hour meter should have about 81 hours on this. I have no idea if this looks good or not honestly. any die hard 2 stroke guys that can read this?
 
the first photo tells me he was running too rich or to much low RPM. Run the same jetting for now and check the plug after each ride. The second and third photo don't show to much. The thrust side skirt is what I would like to see if it is scored. But I would not put that piston back in unless you clean it good and check the clearances. Including the piston pin.

Sam
 
greeneggs&ham said:
the first photo tells me he was running too rich or to much low RPM. Run the same jetting for now and check the plug after each ride. The second and third photo don't show to much. The thrust side skirt is what I would like to see if it is scored. But I would not put that piston back in unless you clean it good and check the clearances. Including the piston pin.

Sam
Click to expand...

I don't plan on ever reusing it. I was just curious if anyone thought it looked weird because I have no idea. The guy I bought the bike from used it for TORCS which I'm not really familiar with so it has a fmf gnarly and the turbine or whatever one has the spark arrester. it's set up for single track stuff and although it been "washed" if been finding lots of pieces of trees everywhere so maybe he did a lot of really low rpm riding
 
Hitting trees is part of it. ;-) but I would repeat don't change any jetting just yet. Figure out what you want to run for a mix brand and a mix ratio and once you start reading the plug you will know whether you need to re jet leaner/richer or just modify you oil ratio to get a clean burn. And a clean burn with little left over oil in the exhaust and on the piston/plug is what you want.

Check the reeds for cracks or for not laying flat on the cage while you have it apart.

Sam
 
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