83 vf750s - hydraulics, manual, etc.

[Shuriken]

Anyone have experience with brakes and clutch on an 83 vf750s?

My friend wrecked his bike a couple of years ago and smashed up the master cylinders. I have some used replacements. Is there a trick to bleeding both systems? I can't get any pressure in the hoses; I'm beginning to wonder if both MCs are no good.

The only other thing I can think of is to vacuum pump the fluid through the system from the lowest screw.

Ben

[petejw]

Hi Ben,
Have u tried bleeding the master cylinders first,
U can do this in 2 ways, either with it installed
on the bike or secured in a vice on a bench.
fill the master cylinders with fluid, either cover the
hole with ur finger or crack the bango nut, apply the lever, then block the hole up to prevent air gettin back in before releasing the lever, do this a cpl of times till all air is out of the master cylinder, then bleed the rest of the system as usual.

hope this helps.

[John]

Ben, I have found that removing the M/C from the handlebars, and tipping it so that the banjo fitting is pointing straight down will eliminate that last little air bubble that may be stuck in the very top of the banlo bolt. You will need some help with this, though...What you will need to do is use a C clamp, and while the M/C is tipped, use the clamp to compress the piston back into the caliper. You may need to remove the caliper from it's mount to get the clamp to work. That forces the fluid back into the M/C and that last pesky air bubble will be gone. Just a few days ago, I replaced the front M/C on the Bag lady, and by using this method, the system bled out on the first attempt.

[Shuriken]

Thanks for the replies.

I'm most concerned that I can't seem to get any pressure build-up at all. I'm really starting to question the master cylinders....

Ben

[petejw]

You wont get any pressure until
you bleed the mastercylinder,
not to say that the rubbers could b buggered.

[Shuriken]

Thanks. I'll try these suggestions. I did find rebuild kits if I don't have any luck.

Ben

[Miti-Babe]

Ben

Rebuild kits have their place, but in my experience, they're rarely needed...

I'd pull the master cyl(s) down and take a look see to check that there is no obstruction to the fluid getting into the cylinder...

There are two holes in the bottom of the reservoir, leading into the cyl... The larger of the two holes is where the cyl gets fluid through, the smaller is the "bypass" which allows the fluid to return very slowly as the pads back away from the rotors...

If these are clear, and the cyl is clear, the only other thing to look out for is dirt or damage to the cyl wall or piston seals... If it all looks OK, it probably is OK...

I've also had good results from letting the system "bledd itself"...

Connect the system together, all bolts tight...

Loosen the bleed nipple at the slave cyl...

Attach a bleed hose and jar to collect fluid...

Make sure the reservoir is full

pull the lever back to the bars... tie it there (I use a slice of inner tube a warp it around tha bar/lever a few turns...)

Leave it a few hours - overnight is good...

When you come back, like as not there will be fluid in the jar...

Tighten the bleed nipple prior to releasing the lever and add fluid to the reservoir too...

I actually bled my XS1100 using this system and it needed no other tweaks..!! Most probable result is that it'll need final bleeding afterwards, but it's always worked well for me...

Hope this helps & Good Luck!

Miti

[Shuriken]

Thanks for the reply, Miti. I will see what I can do tonight and tomorrow and will post back.

Ben

[Shuriken]

Hi everyone,

Thanks for the replies.

I used a hand-held vacuum unit and was able to get the clutch MC working very well. Now that the clutch is back to life, the only real issue left is the front brakes. But no matter what I try, I can't pressurize the system. I tried all of the suggestions and even used the vacuum pump, all to no avail.

I can press hard on the brake master cylinder exit port. When I squeeze the handle down to almost the handle bar, I can start to feel some pressure on my finger. I don't know how much pressure a new master should make.

I'm not sure how these vf750 masters are adjusted, but I may be looking into disassembling it for inspection/cleaning, including the hoses and the balancer device as well. The other thing I was considering is to remove the front calipers to compress the pistons.

I really don't think the lines have enough fluid in them. That of course is the purpose of bleeding the lines, but I'm beginning to wonder if there is a serious blockage of some kind in the lines. I believe I should be able to connect the pump and be able to draw the fluid out of the reservoir, but I can't.

Ben

[Shuriken]

I'm pretty sure the front brake master is faulty. Not sure if it's worth a rebuild.

Ben

[MacMcMacmac]

If you are sure all the air is out, put the cap back on the reservoir when you pump it. You might be pleasantly surprised.