xj650 master cylinder questions

my brakes are horrible... after new caliper and rotor and bleeding, im guessing its in the plunger. was looking to get a new unit, but figured the 19$ rebuild kit would be sufficent enough. problem with both is im not sure on the BORE size on the line. anyone have any ideas? last thing I want to do is buy one online to have it not work.

 

PM our parts guru Chacal, he'll get you the right parts the first time. Have you considered replacing the old rubber brake lines with new ones? Old lines can and will swell when the brakes are applied causing the brake lever to feel spongy even after repeadly bleeding. He has them also.

 

i have brakes, but they drag.... not lock up. thats why i figured it was the plunger in there. its almost killed me 50 times aand its time to fix. lol. the lever goes all the way to the bars. slows me down but not quickly.

 

i am not sure but single disc xj should be different then the rest. Chacal can tell him for sure

 

Sounds like its time for a caliper and master cylinder rebuild. Draging brakes are probably from the caliper sticking. Would not hurt to rebild both.

 

calipers new. they arent sticking.. its just that when you put the brakes on, its more like you drag to a stop rather than lock it up. caliper rotor have been done. just ordered the rebuild kit for master cyl. if this doesnt work ill try the lines

 

The stock front brake system on the 650 Maxims will rarely be able to be "locked up", even when brand new (except on wet roads, etc.).

 

were they working good before the rebuild . Some time it can be a real bear to get them bled correctly

 

you know what i mean though. when you jack the front brakes.... you should stop. this doesnt. lol. all the way grabbed at 20mph still takes 20 ft to stop

 

nothings been rebuilt yet. thought maybe it was a glazed rotor, didnt work.. thought it was the caliper not functioning, replaced that.. nothing... bled and bled and bled.. still there. now trying to rebuild master cyl thinking maybe thats it. if it isnt, and its not the lines, im sol and dont know

 

it is probably a good idea to rebuild it just to be on the safe side. Price of a kit is worth your life any day. I see a lot of people that would just forget about it. Glad to hear your trying to get it right best of luck

 

ifonly, when you rebuild take a good look at the Master Cylinder bore. After these bikes sit for a long while the bore can pit. If it pits the piston will not seal well. if the pits can not be honed out you should replace the Master Cylinder.

 

yes please let us know how your piston bore looks. i have had a post running now for a coulple of months about my brakes not working, just like yours. i have rebuilt the calipers, rebuilt the mastercylinder, and bled for a long long long time.and i still dont have brakes. i took the master apart again and with a light shined it down the bore, being as the bore is so tiny i cant conferm i i have pitting or if what im seeing is another hole thats supposed to be ther. so anyway when you get yours apart let me know how many large holes you have in the master cylinder bore. please!!!!

 

You keep mentioning you "replaced the caliper." With what?

One from eBay? It probably needs to be rebuilt.

 

These brakes are a bugger to bleed. I use a bleed kit I got off ebay - basically a big syringe to pull fluid through, saves a lot of time and effort. Otherwise get a one-way bleed valve.
I spent ages on mine after rebuilding the calipers and m/cyl - now I use this piece of kit on all my bikes - messy, but effective and quick. If your lever comes back to the bar I would think your system is full of air. Braided steel lines will make a difference and are probably less expensive than OE lines.

Nige

 

UPDATE!!! i bought the rebuild kit. to answer one question... i only have 1 hole in there.... but the resivoir looks like 2... but only one. judging by all the rust, Im hoping this is my problem. Ive yet to put it back on the bike and check. being a car mechanic, I would agree that by the lever going almost all the way to the bars, that its full of air... but it had none in it. I bled for a good half hour with a buddy, and a half of a bottle of fluid later, same thing. I replaced caliper with a new caliper. sorry im just responding, I must not have hit show when response is posted. lets hope for the best, and I will update you with wether they work or not... but i must say, by feel.... it seems alot smoother. there was a good amount of rust on everything

 

didnt work. still a nightmare!!! guessing its either the cyl has pits, or theres more problems. im done guessing... i quit!

 

My MC was slightly pitted and it would not bleed properly. I replaced the MC with on from Mikes XS. What a difference. Not to expensive when you consider it is your brakes! http://www.mikesxs.net/products-71.html#products

 

i need to know the bore size though dont i? only two i see says 12.9 and the other 13mm bore... or does it matter?

 

I have a dumb newbie question here. Why is it so hard to get air out of the brake lines, shouldn't it just rise up to the MC and bubble out over the diaphragm?