Master Cylinder on my 800?

[bedrich7]

Hey,

I'm putting a front brake set-up on a vulcan 800 A that I bought without one (don't ask why). So I bought a full set-up (caliper, brake line, and master cylinder) off ebay from a wrecked vulcan and i think the master cylinder is busted. I didn't know how to bleed a brake line so I had a mechanic friend of mine walk me through it and together we got some pressure to the front brake. But after letting it sit for about 20 seconds, the pressure isn't there anymore and you have to pump it to get it back in the line. And on my other 800, you can't even pull the lever all the way to the grip. This one pulls all the way to the grip even at it's top pressure.

I have another caliper I can throw on there to narrow down the problem, but i'm pretty sure it's the master cylinder because it's got some pretty good road rash on it. Seems like the bike it came off of was layed down pretty good on its right side and could have jammed something pretty hard in the master cylinder. There isn't any leaks or anything.

Does anybody have any ideas?

Also, can i use a different master cylinder from a honda or yamaha on my bike as long as it's a similar weight size or cc size bike it's coming off and the bolt for the brake line fits?

[endl98]

sounds like it still has some air in there. what i do .
(1) i take the cap off the master
(2) fill the master to the top
(3) i open the bleeder on the caliper, let gravity bleed while topping off fluid
(4) i close the bleeder then open and slowly pull the lever in then close bleeder. repeat 4 times, fill fluid
(5) pump the lever 5 times and while holding in , open the bleeder, fill fluid and repeat twicce,
usually good after that.

you should have a firm lever. if it fails again after a few minutes than the master needs to be rebuilt , a very easy task.

[bedrich7]

how easy?

Originally Posted by endl98

sounds like it still has some air in there. what i do .
(1) i take the cap off the master
(2) fill the master to the top
(3) i open the bleeder on the caliper, let gravity bleed while topping off fluid
(4) i close the bleeder then open and slowly pull the lever in then close bleeder. repeat 4 times, fill fluid
(5) pump the lever 5 times and while holding in , open the bleeder, fill fluid and repeat twicce,
usually good after that.

you should have a firm lever. if it fails again after a few minutes than the master needs to be rebuilt , a very easy task.

[Bob Myers1]

Sounds like air to me as well.Another method;Go to Home Depot/Lowes and buy a length of small diameter hose small enough to fit over the nipple end of the bleeder, run the other end up to the open top master cylinder and secure it where if any fluid comes out it will return to the master. crack the fitting open about ½ turn and slowly squeeze the brake lever as far as it will go watching the hose. When you see no more bubbles being expelled tighten fitting . Make sure master is full to within ¼ of the top during this.

[bedrich7]

I'll certainly try that. I bled the emmer effer for like... 20 to 30 minutes though.. just seems like it's busted to me.. But thanks for the tips. I'll definitely try them all. Probly tomorrow. I'll report back. Thanks guys.

Originally Posted by Bob Myers1

Sounds like air to me as well.Another method;Go to Home Depot/Lowes and buy a length of small diameter hose small enough to fit over the nipple end of the bleeder, run the other end up to the open top master cylinder and secure it where if any fluid comes out it will return to the master. crack the fitting open about ½ turn and slowly squeeze the brake lever as far as it will go watching the hose. When you see no more bubbles being expelled tighten fitting . Make sure master is full to within ¼ of the top during this.

[Joram]

Bedrich,

1. look for any leaks. If it has lots of road rash, the aluminum casting could be broken. Rebuild will not fix this.

2. I plan on changing out my Master Cylinder on my 800 this weekend. Putting in a new one with a clear sight glass. My original Master Cyl is working fine right now, just the sight glass is scratched and foggy and I am a bit of a perfectionist.

If you are interested in purchasing, send me a PM with address so I can get a quote on shipping. I will sell with or without the lever bar (your choice)

I will post pics so you can see what I am offering. I perfer PayPal.

[mcwrath]

There are 2 tiny holes at the bottom of the master cylinder that may clog if your fluid is not clean, thus not allowing the fluid into the line where it is needed. Underneath these tiny holes is a tiny plunger that forces the fluid down the line. It could be the plunger is malfunctioning too. If a good thorough cleaning fails, then I would replace the master cylinder. I would also not recycle brake fluid. Its cheap enough, you should use fresh fluid every time.

[endl98]

Originally Posted by bedrich7

how easy?

as easy as removing the c-clip and pulling out the plunger/ spring and replacing the 2 rubber cups and reinstalling it. if it sat there could be a jelly like crude in there gumming up everything.

[moparman]

Sometimes just pulling it apart and cleaning the parts and reassembling etc. is enuf to fix it. New fluid and bleed as Bob suggested. Tapping the metal/line so the air works its way up helps too.

[bedrich7]

I'll try that. Joram offered me his working master cylinder so I think i'll go with that. But I am going to tear into this one and see what the problem is. Maybe I could fix it up and have it as a spare, but I'm kinda on a time crunch with this bike. So yeah. Thanks for all your suggestions guys. Always such good information, especially when I am stuck and need help with something difficult to the learning guy like I am.

Originally Posted by endl98

as easy as removing the c-clip and pulling out the plunger/ spring and replacing the 2 rubber cups and reinstalling it. if it sat there could be a jelly like crude in there gumming up everything.

[moparman]

This place is the VERY best for that, for sure. Without the great folks here helping and encouraging me, I might still be working on my 800 trying to make it to Red Lodge (started back in 2005 BTW).

[Joram]

Originally Posted by bedrich7

Joram offered me his working master cylinder so I think i'll go with that.

Did it come in the mail yet?

[bedrich7]

I don't believe so. I'll check and let you know when it arrives. thanks again.

[Joram]

did you receive the master cylinder yet??

[bedrich7]

I believe he did (gun). He hasn't had a chance to install it though. Thanks a ton! He says it looks great. This forum came through on a lot of great things for that vn800A project. Handlebars, grips, master cylinder, cables.. and endless amount of help with other things as well. Great place with great people.

[speedntriple]

New river cycle salvage offers replacement glass lens for your brake or clutch master cylinder if you ever need one. I've sent my buddies there after they've had theirs powdercoated or chromed and the old lens went to peices.