Bleeding Vulcan brakes a royal PITA - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 05-08-2012, 12:55 AM Thread Starter
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Thumbs down Bleeding Vulcan brakes a royal PITA

Now I know why so many guys complain what a PITA it is to bleed the brakes on the Vulcan! Maybe all motorcycle brakes are a pain I don`t know. This is the first bike I have ever worked on. My cars and trucks were never this much trouble to bleed. I never had an auto that took more than ten minutes to bleed after opening the system to replace some component. I spent an hour or more bleeding the two front brake lines on the bike and they are still spongy.

My first mistake was letting the fluid get too low in the mc after opening the left bleeder valve to try a gravity bleed. The fluid flowed well just from gravity. TOO WELL, apparently, because the small mc only holds about 2 ounces of fluid and it drains pretty fast. I discovered a little bit of dry crusty stuff inside the mc which cleaned up well with some scraping with a pocket knife, sucking up the crud and liquid with an eye dropper, and wiping the balance out with a few Q-tips.

I will let it sit until tomorrow and see if any air bubbles rise and disappear over night. Yeah, right, that will never happen for me.

I hope I don`t have to do the reverse bleed I have read about, where new fluid is squeezed in the bleed valve from a plastic bottle, and fills up to the mc.

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

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post #2 of 13 (permalink) Old 05-08-2012, 01:02 AM
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...and I have to replace the MC on my 90. I have it ready to go, but I don't want to deal with all that!

1986 Kawasaki Vulcan 750
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post #3 of 13 (permalink) Old 05-08-2012, 06:56 AM
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Quote:
Originally Posted by OlHossCanada View Post
Now I know why so many guys complain what a PITA it is to bleed the brakes on the Vulcan! Maybe all motorcycle brakes are a pain I don`t know. This is the first bike I have ever worked on. My cars and trucks were never this much trouble to bleed. I never had an auto that took more than ten minutes to bleed after opening the system to replace some component. I spent an hour or more bleeding the two front brake lines on the bike and they are still spongy.

My first mistake was letting the fluid get too low in the mc after opening the left bleeder valve to try a gravity bleed.
Well, it's alot easier if you don't make mistakes....

The real problem with the system is the "junction block" that splits the lines... It seems to like holding bubbles. If you think the Vulcan brakes are a bitch to bleed, you should try doing a set of ABS brakes that have a linked front/rear......

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post #4 of 13 (permalink) Old 05-08-2012, 09:29 AM
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Hoss, I'd say that motorcycle brakes are worse than automotive brakes. IMO, they are all a pain unless you've got a second set of hands/eyes. I've been fortunate to have a wife who is a pretty fair hand out in the shop. She does a lot to keep my cussing to a minimum, both through her assistance and mere presence

You can bleed extra air by loosening the banjo bolts just a hair. Have the bleed valve closed (so you build pressure). Start at the top and work your way down. Squeeze the lever and hold/tie it. Loosen the banjo bolt so it just seeps some fluid. Air, of course, will come out easier/first. Once you get the first couple drops of fluid forming, you should be good. Tighten the bolt then release the brake lever. Repeat, working downward. Be sure to keep an eye on the master cylinder as you work.

Back when I first got started with bikes, I was told they put a banjo bolt in all the places air likes to collect for just that reason.

Best of luck,
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post #5 of 13 (permalink) Old 05-08-2012, 10:11 AM
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I will let it sit until tomorrow and see if any air bubbles rise and disappear over night. Yeah, right, that will never happen for me.
Did you tie the lever back? I couldn't believe how much that firmed it up for me.

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post #6 of 13 (permalink) Old 05-08-2012, 10:55 AM
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Do as Roach says if you are leaving it over night tie the brake lever back in the on position and leave MC top loose, sometimes works a treat as it lets the air out the MC
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post #7 of 13 (permalink) Old 05-08-2012, 12:21 PM
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They do suck when trying to bleed them ,I usually skip all the torture and reverse bleed them from the start. Seems like a lot less hassle and I end up saving time overall.Don't forget how good a paint remover brake fluid actually is.That can ruin a good day quick.




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post #8 of 13 (permalink) Old 05-08-2012, 02:26 PM
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when i got my 86 last week the front brakes didnt even work i opened my bleeder on the right side pulled the brake lever and held it while i used a socket on a long extension to tighten the bleeder then i let off the lever opened the bleeder and pulled the lever and all i got was fluid no air
then i filled the mc and repeated the same on the left side never letting the mc go dry

it took all of about five minutes and the brake is perfectly firm

on a car you tend to pump up the brakes when you bleed them on a bike that creates more bubbles
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post #9 of 13 (permalink) Old 05-08-2012, 10:45 PM Thread Starter
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Thanks for all the responses guys. I talked to TommyV8 today, (a local independant mc mechanic and member of the local bike forum), and got a few tips from him. I went out and slowly squeezed the lever many times while watching tiny bubbles rise in the brake fluid reservoir. The bubbles eventually quit rising, so I tied the brake lever back and am going to leave it again tonight.

Tom suggested prying the brake caliper pistons back too. I tried that with them still mounted on the forks, but it didn`t work.

Maybe I need to take the calipers off and use a "C" clamp to push the piston in.
I need to take the forks off anyway to rebuild/service the tubes, replace seals, etc., and want to polish the lower/outer aluminum sliders at the same time.
What do you all think?
Should I do the fork service/polish and finish the brake bleed when I reassemble it?

Denny, I have two questions for you. What size hose do you use for the reverse bleed?
I have a piece of 1/4" clear plastic hose, but it doesn`t grip the bleeder valve tight enough and leaks even when just trying to gravity bleed through it.
I can`t find any 6mm tubing, which may be what I need.
Just had another idea. Clamp the 1/4" hose tighter with a small automotive fuel line hose clamp. (screw type)

And two, what do you use for a nozzle on the bottle of brake fluid?

One more question. The fluid level sight glass on the master cylinder is crazed and somewhat discolored, making it somewhat difficult to determine how full the mc reservoir is. I know there is a place on Ebay where I can get a new one, but what is the best way to put it in? Crazy glue? silicone? epoxy? or ????

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15


TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/showthread.php?t=9127
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post #10 of 13 (permalink) Old 05-08-2012, 11:56 PM
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Quote:
Originally Posted by OlHossCanada View Post
Thanks for all the responses guys. I talked to TommyV8 today, (a local independant mc mechanic and member of the local bike forum), and got a few tips from him. I went out and slowly squeezed the lever many times while watching tiny bubbles rise in the brake fluid reservoir. The bubbles eventually quit rising, so I tied the brake lever back and am going to leave it again tonight.

Tom suggested prying the brake caliper pistons back too. I tried that with them still mounted on the forks, but it didn`t work.

Maybe I need to take the calipers off and use a "C" clamp to push the piston in.
I need to take the forks off anyway to rebuild/service the tubes, replace seals, etc., and want to polish the lower/outer aluminum sliders at the same time.
What do you all think?
Should I do the fork service/polish and finish the brake bleed when I reassemble it?

Denny, I have two questions for you. What size hose do you use for the reverse bleed?
I have a piece of 1/4" clear plastic hose, but it doesn`t grip the bleeder valve tight enough and leaks even when just trying to gravity bleed through it.
I can`t find any 6mm tubing, which may be what I need.
Just had another idea. Clamp the 1/4" hose tighter with a small automotive fuel line hose clamp. (screw type)

And two, what do you use for a nozzle on the bottle of brake fluid?

One more question. The fluid level sight glass on the master cylinder is crazed and somewhat discolored, making it somewhat difficult to determine how full the mc reservoir is. I know there is a place on Ebay where I can get a new one, but what is the best way to put it in? Crazy glue? silicone? epoxy? or ????
use a new tip off an 80w90 rear end lube bottle,cut it off to fit your tubing ,they usually screw right on the the brake fluid bottle or a clean oil can , one of the little ones with the trigger to squirt oil with the trigger pump works great too.
There are a couple of threads on here about replacing the sight glass,my advice is if it ain't broke or leaking don't mess with it.

The fork polishing ids a couple of days of sanding and polishing work,I'd replace the seals on it ,ride it and save that for next winter.The clear coat is a bear to get off before you can even begin to polish them.I start with 600 grit on a palm sander move to 1000 grit and then 2000 grit wet or dry and then finish them with Meguirs or mothers metal polish and a cloth buffing wheel one clean and one to apply it with,the aluminum will turn black as it pulls the oxidation off and then polish out to a high luster like chrome,after you get them shining, a hand polishing and waxing and they look like new and it only takes a couple of times a summer to keep them that way,polish out your levers and engine covers the same way but you don't have to deal with as much clear coat




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X
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