[-stew-]

So long story short, my 748 has been sitting for about two years. This morning I pull it out of the corner of the garage, change the oil and filter, put in a new battery, air the tires up and pulled it around to the front of my house and gave it a quick wash. I rode it a block to the gas station to fill it with fresh fuel and by the time I rode it a block I pretty much lost all the front brakes. It stops poorly and I can easily pull the lever to the bar. feels like the master has failed.

Are these master cylinders rebuildable? Is the dealer my only option for a new one? I am ok with buying used, but I think buying a used one I'm taking a gamble of being right back where I'm at.


Also the rear brakes don't work. they havent worked as long as I've owned the bike. Does any one have any tips for orientating the caliper to bleed the rear brakes? I'm gonna start with that and see if i can get a pedal out of the rears.

Thanks in advance!!


-Stew

 

[tye1138]

Brake fluid goes bad… first start by sucking out all the brake fluid in the system and sucking new fluid in. I use a high pressure fluid evacuation system on the bleed ports to suck new fluid through the system.

I doubt it needs a re-build.

 

[garylkendall]

master cylinders can be rebuilt if you can find the seals. never seen a rebuild kit for them. usually dont need new seals, if it has been sitting for a long while the fluid may have not only gone bad but gotten chunky. have had a few bikes that have been sitting for a long time and the fluid went so bad that there were chunks of gooey brake fluid blocking the the lines and cylinders pistons ect, had to tear apart the entire system to clean it. first drain all the old fluid out and put new fluid in and bleed the hell out of it. caliper pistons could be stuck as well. try new fluid and a good bleeding first and see what happens. brake fluid contaminates easily especially when sitting. a minivac bleeder works well or you can do it the old fashion way. make sure you see no air bubbles in the bleed tube. i bought a used master cylinder for my 748, worked no problem. to bleed the rear sucks. you have to remove the caliper and turn it right side up so the bleeder cap is on top instead of the bottom. this takes 2 people to, unless you are really talented like me ha ha ha, one per son has to pump the master cylinder and hold it while you crack the bleeder cap and hold the caliper. i was actually thinking about flipping the caliper bracket upside down and having the caliper on top for any future bleeding. you will need a rear stand as you have to remove the wheel while bleeding the rear caliper. the front brakes have a bleeder cap on the master cylinder as well, you need to bleed this first or your front caliper will never bleed out. if it doesnt have a cap on it you can just crack the banjo bolt while holding the brake lever and watch for fluid to squirt out, make sure you have rags wrapped around everything as this can get messy.

 

[-stew-]

Thanks for the info. Ordered a rear stand last night so that should make life easier for a lot of things. I'll cross my fingers and try flushing the front out with fresh fluid. What size are the Allen head screws holding the windscreen on? Looks like taking that off will give me room to work up at the master.

 

[tye1138]

Thanks for the info. Ordered a rear stand last night so that should make life easier for a lot of things. I'll cross my fingers and try flushing the front out with fresh fluid. What size are the Allen head screws holding the windscreen on? Looks like taking that off will give me room to work up at the master.

The wind screen to fairing interface is very fragile. The sun messes up the plastic. You most likely won't be able to take it off and put it back on without cracking something.

Its far easier to pull the whole nose off. There are three screws underneath, the two mirrors and then the dzus fasteners down the L/R side and the whole nose pops off. I've never had a problem doing this work with the bike assembled however.

 

[-stew-]

Thanks for the heads up. I was figuring pulling the windscreen would make filling the mc reservoir easy and would make bleeding the m/c easy. I think I need to pull the nose anyhow to clean up some clouding on the inside of my headlights.

 

[garylkendall]

you cant get to all the screws for the screen anyway without pulling the nose off. you can pull the nose off without removing the side if you are careful. the allen screws are a special size tool should be in your tool kit if you have one. if not i think the are 2.5mm or 3mm, very small. in fact mine weren't allen heads anyway, mine are t7 torx head screws. get a T7 torx screwdriver tool from sears. couldnt find an allen wrench that would work with a torx screw that size without stripping head out. its easier to remove the nose anyway. i had some nasty clouding on the inside of my headlight too. remove the head from the bucket and remove the bulbs, i used a small rag wrapped around a big flathead screwdriver to reach inside to wipe as much as i could. i bleed my front brakes with nose on enough room to work with, just make sure you keep the brake fluid filled up while bleeding or you will get air in the lines and start over

 

[-stew-]

Came home tonight and ran almost a quart of brake fluid through it, master is shit. It pumps bubbles out of the bleeder on the master constantly.

 

[-stew-]

I have some more questions.

There is a 996 service manual for sale local to me. How much info in this will be useful to me and my 748?

I just got a Pit-bull rear stand for the bike. I am amazed by the quality of it for one, but I'm just wondering if I have to have any worries while servicing the bike on the stand? Do I need to take any precautions when breaking bolts free doing valve adjustment, timing belts, pulling the rear wheel, ect.

 

[garylkendall]

they should be similar with the major difference being the engine size

 

[super dooper]

You should be fine with servicing your bike on the stand, I do it all the time. If I am going to be pulling, prying, or torquing something I usually put something heavy on the stand handle like a sandbag, child or lazy buddy. Someone said you have to remove the rear wheel to bleed the rear caliper, No you don't. As stated previously just unbolt from carrier place it higher and bleed until you are happy.

 

[garylkendall]

yes you do, first i could get the bolts off due to the wheel blocking them. second, air stays at the top and fluid stays at the bottom, the bleeder cap is on the bottom so the fluid will come out without bleeding the air out. thats why the bleeder cap is on the top of every other bike except ducati for some reason.

 

[-stew-]

BACK IN BUSINESS! Master came today, got that on and bled out. Got the rear brake bled out and I think it's working. Did not have to remove the rear wheel. Snap-on 1/4 inch drive 12MM socket is thin enough to get by the swing-arm and get on the bolt. Rotated the caliper up onto the top of the rotor, zip tied it in place. Sucked all the old fluid up and out through the caliper bleeder with a syringe. Brake pedal feels ok by hand, and the caliper clamps the rotor. Bled the clutch out the same way with the syringe. New used upper and lower right side plastics to replace the rashed up ones that came on the bike. Bike looks like a million bucks! Now its time for a test ride and find some wings!

 

[-stew-]

Are the rear brakes on these bikes terrible, or is mine not right? It works, but barely. I can't lock the rear tire.

 

[selbitz748]

Did you paint your stock wheels black?

 

[garylkendall]

my rear brake works fine on my 748. maybe you have some lingering air in the caliper, took a long while to bleed mine. you may also have some gunk in your calipers too. rebuilt mine last weekend and all kinds of junk in the caliper that you cant bleed out. brake fluid should be changed out once a year, brake fluid gets contaminated by water in the air. you cant stop it but you can prevent problems by changing you fluid every year, which means bleeding your brakes thoroughly.

 

[-stew-]

There's no air in there. The pedal is firm, and the action is instant. The fluid that came out was nasty. I'll try bleeding it a few more times to flush things. Maybe the piston is sticky and all gacked up.

The wheels were powder coated black by a previous owner. I'm adding a couple of stickers. The bike needed some color.

 

[-stew-]

Pic.

 

[juan1]

nice to see you brought it back out

 

[garylkendall]

you could have a stuck piston on the rear. had that problem, had to disassemble the calipers to clean the seals and the junk that collects in calipers