front brakes are "grabby" - any ideas? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 05-19-2010, 09:19 AM Thread Starter
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front brakes are "grabby" - any ideas?

I've found that the front brakes on my 1994 VN750 are pretty grabby. I only have to pull the lever in about 1/4 of the way for a lot of braking, by halfway it's like fully locked. I've bled out the brake fluid but it didn't help. It's been like this for a while - probably since the bike was knocked over while parked in the street by assailants unknown about a year ago (who then picked the bike up at least).

I mentioned this last year to a dealer mechanic when I brought it in for a carb cleaning after it got gummed up from rust in the tank and he said, "seems normal to me". (Of course this is the same dealer mechanic who said "seems normal to me" about my 2004 VN750's vibration issues that turned out to be a factory-misinstalled balancer, where the vibration actually was bad enough that the fuel tank had developed a hairline crack near the mounting point to the frame...)

I did some Googling on this topic and found this on an H-D board: I Had to replace the Master Cylinder the inside walls were out of round (had a low spot on one side). wouldn't let the brake back bleed in to the cylinder.

Huh, that hadn't occurred to me. Does that ring true? The bike fell onto its left side, where I replaced the bent clutch lever and then straightened the fork, so I didn't think about why the right side of the bike might have any problems, but maybe it was actually hit on the master cylinder by whatever car or truck clipped it to knock it over.

How would I test for this, and how hard is it to replace the Master Cylinder? (Bleeding the brakes is kind of a time-consuming pain as it is.)

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Last edited by robardin; 05-19-2010 at 09:30 AM.
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post #2 of 16 (permalink) Old 05-19-2010, 09:23 AM
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Well, Robardin. Myself, i would spray the surfaces with brake clean and make sure its not contaminated...and inspect the pads if possible. I put speed bleeders on my bike so its easier to bleed them...i put all new brake fluid in mine ...it was easy just put a tube on the nipple and drain the excess into a beer bottle. I would just make sure its good and flushed and replenish with proper stuff. There is a thread on here somewhere about it. Dont forget to tie the brake lever down overnight...helps get the air out.

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post #3 of 16 (permalink) Old 05-19-2010, 12:01 PM
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Ya sure you don't have too much fluid in the master cylinder?
Also could be cheaper brake pads causing them to grab.
Have you measured the brake discs? Don't know if those being below safe levels would cause issues, but wouldn't hurt to check.


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post #4 of 16 (permalink) Old 05-19-2010, 03:43 PM
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I'm all for the "too much fluid" theory myself. That will give you exactly what you are experiencing assuming nothing is actually broken or worn out. Bonus - it's the easiest thig to check via the sight glass.

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post #5 of 16 (permalink) Old 05-22-2010, 04:29 PM Thread Starter
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Well the brake fluid level looks OK based on the level sighting on the master cylinder - it's right at the LOWER line in fact, if I drain significant amounts it'll dip below that... Maybe after a trip to get some DOT 4 at AutoZone tomorrow.

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post #6 of 16 (permalink) Old 05-22-2010, 05:02 PM
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I've found that the front brakes on my 1994 VN750 are pretty grabby. I only have to pull the lever in about 1/4 of the way for a lot of braking, by halfway it's like fully locked. I've bled out the brake fluid but it didn't help. It's been like this for a while - probably since the bike was knocked over while parked in the street by assailants unknown about a year ago (who then picked the bike up at least).
-----------------------------------------------------------------------------------------------------------------------------------------------------

OK this is just happening since the bike was knocked over, and the grabby brake is the primary problem.

I tend to agree with Kimmerling about cleaning the disc. I would also pull the calipers and take a good look at the brake pads. You can try cleaning them, but if they are contaminated with brake fluid or oil, etc., you will probably have to replace them to eliminate the grabby condition.

I don`t think any excess amount of fluid in the reservoir will affect hydraulic pressure developed by pulling the brake lever, which acts against a master piston in the master cylinder. The fluid in the reservoir is not under this pressure.

Is the distance your brake lever moves now a problem? Has it changed since the tip over? I just checked my brake, and it seems to move about 1/4 of the way to start feeling significant resistance, and 1/2 way would be a lockup. Yours seem to be about right.

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post #7 of 16 (permalink) Old 05-23-2010, 12:10 AM Thread Starter
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Quote:
Originally Posted by OlHossCanada View Post
Is the distance your brake lever moves now a problem? Has it changed since the tip over? I just checked my brake, and it seems to move about 1/4 of the way to start feeling significant resistance, and 1/2 way would be a lockup. Yours seem to be about right.
OK then I guess it's my 2004 bike that has overly soft brakes. On that bike, I have to pull about halfway to feel a lot of resistance and pretty much nearly all the way to the grip to get a lockup.

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post #8 of 16 (permalink) Old 05-23-2010, 08:15 PM
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I have a couple posts on here about replacing the master cylinder and brake bleeding. I would be rebuilding the calipers, especially if it's never been done. The fluid turns to gel over the years and if you haven't taken the calipers apart I bet you find a gel-like substance in there. I rebuilt mine, it's extremely easy to do. I bought new pistons and seals at cheapcycleparts.com (where I bought all my VN750 parts). Then I'd rebuild the master cylinder and pay particular attention to that ultra tiny hole in the shallow dimple in the master cyclinder; this is thre return hole and if it gets plugged you will have problems. Blow everything out with compressed air, clean real well with fresh brake fluid and put everything back together. Get yourself a set of Speed Bleeders and you can bleed the wheel cylinders yourself, bleeding the master cylinder is also easy, the Clymers Manual has a good section and instruction on it (or look up one of my earlier posts). Good luck - don't mess around second guessing the brakes - tear it down and rebuild them, they are 16 years old and need a good cleaning.

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post #9 of 16 (permalink) Old 05-24-2010, 06:21 PM
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I can't believe I missed it first time around. Have you checked your fork alignment? If it happended since a knock over, maybe the forks are just a tad off, causing some binding?

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post #10 of 16 (permalink) Old 05-25-2010, 04:23 AM
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First of all, this is just my opinion, not advice, so please don't take it that way. I noticed the front brake was grabby from the first day I bought my brand new '93 Vulcan 750, and it stayed that way for over 80,000 miles, and several sets of brake pads, cleanings, and fluid changes. Different tires made no difference. I decided that the Vulcan 750 simply had too much front brakes for it's size.


When I bought my '02, it felt the same way. Just barely squeeze the brake lever, and it wanted to lock the front wheel. Very touchy. Rear brakes on both bikes were fine. Finally after putting about 20,000 miles on the '02, I decided to try something. I completely removed the left front caliper and hose. The brake suddenly felt normal, and worked fine. I did extensive testing at a large open area free of traffic, including controlled stops from an indicated 100 mph with the front wheel held on the verge of lockup. It worked fine every time, and stopping distances were uneffected. I went ahead and removed the rotor, and have since put over 25,000 miles on it, under all kinds of conditions, including a lot of stop and go city riding, mountain riding, and long trips. The brakes have performed flawlessly. They do not overheat, they do not fade, the pads do not wear out any faster (and now the front brake only requires one set of pads) there has been no noticeable rotor wear, I have been in a lot of close calls since then, and the brakes worked perfectly every time, holding the wheel right at lockup, where it would have locked up before, with both discs.


Quite simply, I think dual front discs are overkill on a bike the size and weight of the Vulcan, though they could have been made less touchy. Many much larger bikes have less front brake swept area than the Vulcan 750 does, and stop just fine.


Now, under no circumstances am I even suggesting anyone do this, only that it has worked fine for me, and has been proven safe (IMO) by 25,000 miles of day to day use. As with any other modification, if you do it, you do it at your own risk. But I can't see how what I did is any more dangerous than a brake that almost locks the wheel (not a good thing) every time you touch it. Jerry.

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