Motorcycle Repair: 1982 VF750C Clutch Problem, tiny air bubbles, v45 magna

Question
Hey Chris,

    I've got a '82 V45 Magna.  The last time I rode it, it was riding pretty well.  I then didn't ride it for several months.  Now, the clutch won't disengage and the clutch lever is spongy.  The bike has about 22, 000 miles on it.

    First of all, I'm a complete newbie at motorcycle repair.  I wanted to work on my bike to learn more about it.  So, I bought the manual -- *grin* -- and am going to town.

    As you probably know, it's a hydraulic clutch.  There are no external leaks in the system that I can tell.  I've rebuilt the master cylinder.  I've disassembled and cleaned the slave cylinder – the piston seems to slide well.  Bleeding the clutch releases tiny air bubbles.  It seems that no matter how much I bleed it, I still get tiny bubbles.  I think I've gone thru ½ a can of Dot 3.  (And given the original problem – the clutch failed by just sitting – I don't think the problem is really air in the line.)

I've disassembled the clutch itself and found the plates were stuck together.  But, they came apart with only a little effort and the surfaces were clean.  I coated the plates with oil and reassembled the clutch – no joy.

    At this point, I've hit all three pieces of the system and haven't fixed the problem.  The fact that the level is spongy seems strange to me.  If the plates being stuck together was the problem, wouldn't the clutch level refuse to move?  If I had a hydraulic leak, wouldn't I see dripping somewhere?  If the slave cylinder gasket is not holding, I should fine fluid outside the cylinder, right?  (I don't seem to be losing fluid from the reservoir.)

  I'm stuck – and in need of some expertise.

Thanks,
Bob


Answer
Hi Bob.
 Your problem is not in the clutchplates.  It is in the hydraulic clutch assembly.

 The manual gives you a fairly easy to understand walk-thru of the bleeding proceedure for the clutch and brakes, But, here's the part they don't tell you;

Some bikes have an additional problem with both the clutch and front brakes, including my own on my V65 Magna.  The problem stems from the configuration of the master cylinder, which is that the connection to the hydraulic line at the master cylinder creates a pocket that air bubbles like to hide in (this is called a reverse trap) and the method for bleeding that section is a little tricky if you've never done it before.

 Here's the proceedure;

1) Bleed the system like normal.

2) Put a wrench on the banjo fitting and squeeze the lever.

3) (NOTE: Use a box end wrench for this) While holding the clutch/brake lever in, crack loose the fitting and reclose it quickly. Have a rag over the fitting connection that you are working on because it will spit at you as pressure expells the air and a little fluid.

<<<<<<<IMPORTANT NOTE: DO NOT release pressure on the lever till the fitting is tightened back up or you will suck air back into the line.>>>>>>>

4) Test the clutch/brake again.  If done correctly, you will have pressure near the beginning of the lever movement, like it should be, rather than at the end.

5) repeat as needed, but you should not need more than 2-3 times to get the system working correctly.

If, after 4-5 attempts you cannot get the clutch working correctly, then you may need to rebuild the slave unit of the clutch.  That is an easy fix that will take less than an hour to do once you have all of the parts.

Good luck.
FALCON