Clutch Bleeding

Resurrecting an old topic here, but . . .

This morning I started up the 1984 VF750F, pulled in the clutch lever and realized the lever was more ornamental than operational. I removed the clutch reservoir cover and saw that the fluid level was low - so low that the holes in the bottom are exposed when the bars are turned to the left lock. The line down at the slave cylinder bulges when I engage the clutch lever, so something is happening, but there isn't enough oomph to fully engage the clutch. So, I reckon I have air in the clutch line.

In your experience(s), is it worth filling the reservoir and trying to bleed the system at the top banjo bolt (where the line attaches to the reservoir), or should I just go to the bleeder valve and do the whole procedure?

Alaskan, Apr 22 2008, 07:05 PMThe line down at the slave cylinder bulges when I engage the clutch lever, so something is happening,

Visibly bulges? I would replace it.
I don't know how to bleed at the top banjo bolt (without a bleeder being attached to it) so I'd bleed at the slave cilinder.

Well, not visibly bulges. Perhaps it's more accurate to say that I can feel the line moving when I hold it while I pull the clutch lever.

Just a quick update. I wrapped rags around the clutch line below the master cylinder banjo bolt and bled the system from there. After 4 squeezes, BINGO! The air bubble must have been sitting just at the top of the system. It was a little messy, but the rags caught all the fluid. Interesting that the shop manual only describes bleeding from the nipple on the slave cylinder.

Alaskan, Apr 24 2008, 09:45 AMJust a quick update. I wrapped rags around the clutch line below the master cylinder banjo bolt and bled the system from there. After 4 squeezes, BINGO! The air bubble must have been sitting just at the top of the system. It was a little messy, but the rags caught all the fluid. Interesting that the shop manual only describes bleeding from the nipple on the slave cylinder.

The shop manual wouldn't describe it because it does not bleed the system. It may release air trapped right at the banjo but will do nothing for air trapped elsewhere in the system. it is not a substitute for bleeding the clutch.

Alaskan, Apr 24 2008, 07:45 AMJust a quick update. I wrapped rags around the clutch line below the master cylinder banjo bolt and bled the system from there. After 4 squeezes, BINGO! The air bubble must have been sitting just at the top of the system. It was a little messy, but the rags caught all the fluid. Interesting that the shop manual only describes bleeding from the nipple on the slave cylinder.

Bleed at the nipple on all the hydraulics. Did mine last weekend and ended up with about a pint of fluid that looked like dark rum and that's on a 2005. chased a few little bubbles out of the system, system is a little firmer as a result. Oh and by the way color of fluid through the sight glasses on the handlebars is very deceiving. Also bleeding at the slave end is way less messy.

Right. I understand you can't fully bleed the system at the master cylinder. I was looking for a shortcut to get my clutch back. I found it when I bled a tablespoon of fluid - and air - at the top banjo bolt. Worked like a charm and took about 2 minutes.

I'd still bleed the system properly. Just because it's your beater bike doesn't mean it don't need love...

SEB, you are my conscience! lol

Alaskan, Apr 24 2008, 06:35 PMWorked like a charm and took about 2 minutes.

With a miti-vac, you can do a clutch full flush in under 5 minutes (no kidding).

Now that's a good idea! Which Mityvac model do you use? There are quite a few listed on the company's webpage.

Whichever one they had at the autoparts store when I bought it several years ago. (IMG:style_emoticons/default/biggrin.gif) It's pretty nasty now from numerous uses plus numerous cleanings with brake cleaner (gauge face is opaque) so I've been thinking about getting a new one too.

I'm getting some late and abrupt clutch engagement once in a while.....almost like I release the lever and get on the throttle where I expect it to engage and nothing....than just as the revs climb, bam....engagement and a launch. Could it be air in the system?

Car54, Apr 25 2008, 09:37 PMI'm getting some late and abrupt clutch engagement once in a while.....almost like I release the lever and get on the throttle where I expect it to engage and nothing....than just as the revs climb, bam....engagement and a launch. Could it be air in the system?

i get this in 1st gear on my track bike.....i am interested in the reason too... (IMG:style_emoticons/default/lurk.gif)

Bump for some tips!

I have the Mityvac "Silverline," and it's worth every penny of whatever I paid for it many years ago:

Mityvac Silverline

Here's my clutch bleeding technique:

1. Remove left fairing to gain good access to the clutch slave cylinder bleed screw.
2. Turn the bars all the way to the right with the bike on the center stand.
3. Tie a rag around the perimeter of the master cylinder reservoir in case of spillage.
4. Remove the master cylinder cover and diaphragm.
5. Using a 10 ml plastic syringe (baby oral medication syringe, available at drug stores), and suck out all of the old fluid from the master cylinder.
6. If there is sediment in the bottom, use Q-tips tips to carefullly swab out the sediment.
7. Fill the master cylinder to the upper line with new Honda Pro Dot 4 Brake Fluid.
8. Attach PVC tubing from the Mityvac receiver cup to the bleed screw.
9. Pump a vacuum with the Mityvac and then open the bleed screw 1/4 turn, allowing the old fluid to flow into the Mityvac plastic receiving cup. NOTE: Tighten the bleed screw while still drawing a vacuum and BEFORE all the fluid is drained from the master cylinder.
10. Refill the master cylinder and repeat step 9 until the fluid bleeding into the Mityvac cup is the same color as new fluid.
11. Be sure to tighten the bleed screw while holding a vacuum and drawing fluid into the receiver cupto prevent air from being introduced.
12. Fill the master cylinder reservoir to the upper line and reinstall the diaphragm and cover.

Note: You will see bubbles in the Mityvac PVC line during the bleeding/filling process. This occurs because air is being drawn past the PVC tube/bleed screw connection. Don't worry about this, as the process above removes all air in the system, even though you don't see a bubble-free flow in the Mityvac PVC tubing.

Follow the same process for brake bleeding/filling per the sequence in the Honda Service manual.