clutch master cylinder puzzle

Hi, all.
So the bike I just acquired (2003 VFR 800 Interceptor) had been dropped in a garage (before I got it) and suffered a broken clutch lever and minor fairing scraping. I could see hydraulic fluid had been leaking from the clutch lever seal which told me it also was damaged.

Not one to shy away from a job like this I purchased a cylinder master cylinder rebuild kit and clutch lever and away I went. The lever was easy once I remembered to re-use the bushing for the pushrod. The cylinder rebuild turned out to be a bit more of a challenge than I had anticipated. Bear in mind, I am flying by the seat of my pants (without a service manual). Here's how it went-

The inner piston, spring and seal rings all went together just as the old ones did so I'm pretty sure I have all that correct. The snap ring was seated properly and I made quite sure there are no leaks around the housing seal area. Likewise with the banjo bolt; I installed two new crush washers, too, and tightened it up. No leaks there.

Two issues arose: there is this little 'L' shaped metal part that was in the bottom of the reservoir, the orientation of which I was not previously aware. I'm told this part is a 'guard'. I re-installed it with the three prongs facing down into the recessed portion on the floor of the reservoir and the 'blade' portion covering but not blocking an orifice. It seemed to fit ok.

The second issue, assuming the first has absolutely nothing to do with it, is that I have gone through about half a quart of hydraulic fluid tring to bleed the system. No matter how many times I pump the lever and crack open the bleeder valve at the slave cylinder, I can't get the pressure up enough to engage the clutch. I can see fluid being expelled into the jar and I watch some bubbles escape the hose, so I assume the piston is pressurizing the line somewhat, but the process doesn't yield the expected result.

I may just be too tired or not as smart as I thought but is there some special technique to this seemingly simple procedure? It should be like any other system that uses brake or hydraulic fluid, shouldn't it?

 

The clutch system should be easy to bleed as the bleeder is mounted on top of the slave cylinder so air naturally rises to that point. If you're not getting any pressure and you're getting fluid pumped out when you break loose the bleeder, then my thought would be a problem with the master cylinder assembly. Maybe a nick in one of the seals/o-rings when you assembled everything? Maybe when the lever broke it also caused a slight distortion in the bore of the master cylinder area.

In any case I would look closely at the master cylinder as the likely culprit.

Here's what the master cylinder looks like:

 

Thanks for the advice. I have rebuilt a few brake cylinders so I took the usual care in re-assembly and inspection.

As it turns out, and this may be purely coincidence, the 'guard' or 'protector' that sits in the bottom of the reservoir can be re-installed two ways. Initially I installed it with the 3 tangs facing downward into the recess on the floor of the reservoir. When I inverted it, I was finally able to get the pressure up and engage the clutch. Maybe just chance.

Anyway, thanks again for the feedback. Next problem, here I come!

 

Forget about the "spit guard," as it can be deleted and hasn't anything to do with your pressure issue.

Anytime a MC, brake or clutch, has beed drained of fluid you should bleed it at the banjo bolt hole and build pressure before hooking it to the rest of the system.

Sure you installed the seals facing the right direction ??

 

I just flushed my old clutch fluid. Below is the process I followed.

1. Use a vacuum bleeder to purge lines and get clean fluid flowing
2. Cycle the clutch lever 10-20 times
3. Perform the traditional process of pump/hold/bleed/release with an assistant to ensure all air is out of the line
4. Cycle the clutch lever another 10 - 20 times and you will start to get pressure
5. Traditional process of bleeding brake line a few more times to ensure compressing fluid is totally air free
6. Cycle the clutch lever and normal function is restored

Jose

 

Most definitely have the seals in the right orientation. Was able to get the system pressurized but it seemed to take way longer and with more fluid than I expected. Clutch operation is now nominal.

So about bleeding it at the banjo bolt hole... just how does one do that? If it is disconnected, I don't see a way of pressurizing the line as it is downstream of the MC itself (where the pressurization begins, I thought). I obviously have a lot to learn.

Thanks...

 

You don't really disconnect the line at the banjo bolt, you just crack the bolt while the line is under pressure. Be very careful to protect any paint or plastic of course. I've not had to do this before but some people have.

 

I did not bleed at the banjo. The key was to get fluid completely in the circuit and pump the clutch handle to get the fluid to start compressing and squeeze out air from the piston. I saw some bubbles coming up when I did the first series of clutch lever cycles.

Jose