Clutch - Intermittent air leak ???

[Triumph1050]

I need some troubleshooting advice or ideas...

At times I need to need to bleed my clutch. I use a mity-vac and sometimes it will last for weeks and other times only a ride or two before needing re-bled.

I've replaced the slave cylinder and cleaned up the masters top edge...it looks fine so I don't even know where the air leak is coming from. A mechanic I've used in the past who knows Vmax's quite well he used to race them thought that maybe there was a puncture or leak in the hose but I haven't seen any and I'm not losing any fluid.

thoughts?

 

[[email protected]]

What about the master cylinder? Is it the original 27year old piece? If so, id consider a rebuild or more likely replacement. Plenty of affordable options on ebay. Probably the same $ as a rebuild kit or even cheaper.

Lines aren't too expensive. If you're on a budget someone here may have a gently used oem line for dirt cheap, just add new crush washers.

 

[Triumph1050]

Thanks for the sugesstions...

I believe it is the original master. the bike only has 17k miles but its an 86 and time does have its own affects regardless of usage. Ill probably replace the master and tubing soon.

Still puzzling why it leaks air in intermittently.


What about this.... once, only once I noticed brake fluid slightly seeping out around the two master cover screws. I do have aftermarket billet covers that say VMAX on them. Do you think that slight seeping is enough to compromise the air seal?

 

[maleko89]

The stock bleeders can go bad too. Might be time to remove and clean and make sure they seal.

 

[ZackDaniels]

What about this.... once, only once I noticed brake fluid slightly seeping out around the two master cover screws. I do have aftermarket billet covers that say VMAX on them. Do you think that slight seeping is enough to compromise the air seal?

The seal on the res covers is more to keep fluid in than air out. Any air that gets in the res isn't going to get sucked down into the hose or anything like that... it's going to stay at the top and seep back out because the fluid is considerably heavier than the air.

It's probably the almost 30 year old res rubber gaskets that need replacing to stop the seeping more than the aftermarket covers. That's nice just to stop brake fluid from dripping on your ride, but shouldn't affect your air in the lines problem.

 

[[email protected]]

The covers are not the problem. The brakes will build pressure with the cover removed. Gotta be an air leak somewhere. Problem is finding it.

If you're considering a new master there are many possibilities. If you are interested in having a clutch that is a bit easier to squeeze you could try a fjr master or concours master. Although they have a bit less travel till it engages. I'm running a zx14 master and like its feel better than oem, fjr, and concours.

 

[Triumph1050]

thanks for all the suggestions...

 

[Fire-medic]

A suggestion-if your fluid level in the master cyl is low, and you leave the bike on the sidestand, w/the front wheel cocked-left (right handlebar is higher than the left) you may be exposing the weep hole in the master cyl & allowing air to enter the line-and there is your issue.

Other than that, I would say, either rebuild or replace your master cyl & use new washers for the banjo bolt. You don't need Yamaha replacements, you can use generic ones from the auto parts store sized for metric fittings, cheaper & easier to obtain. Also, check your connections and consider a new flex hose in stainless steel. You may have a spongy hose internally, it could be trapping some air and intermittently-releasing air molecules into the fluid. Russell makes a good hose. Usually a spongy hose will just expand as you try to exert ressure via the lever, resulting in an aneurysm, or bubbling, of the rubber line which does not allow pressure of the brake fluid to actuate the slave cyl (clutch) or the movement of the brake caliper pistons. Sometimes it may even prevent a release of the pressure and allow the fluid circuit to not release (sticking slave cylinder or brake caliper pistons).

 

[jfeagins]

My bet is on an air bubble that never makes it completely out at the bleeder, then makes its way slowly back to the top to rest next to the banjo bolt where the line attaches to the handlebar master.

Next time it needs bled, try releasing the air bubble at that banjo bolt BEFORE bleeding the system all the way down to the wheel cylinders. See if that don't get rid of the air once and for all...

Then, PLUS ONE to making sure you have high enough fluid level in the master to cover the bottom at all times to ensure no more air can get into the system.

If your bleeders weren't sealing, I'd think you'd be seeing some mess around them from the pressure created by using the clutch long before you'd be having any air entry problems there. IMO.

 

[gamorg02]

i like the bleeder idea or the master cylinder rebuild. speed bleeders come with a thread sealant that might help troubleshoot.

 

[tugla]

a master rebuild or change to newer one im sure is gonna save you headaches in the long run. for sure by now its kinda worn out the body......

 

[Triumph1050]

Ill try that banjo bolt bleed next time.

I keep the fluid full and it doesnt appear to lose any between bleeds and I see no fluid leaking anywhere.

Ive suspected a persistent air bubble and that could explain why its so intermittent.

Question.... several of yall have mention bleeder"s" plural. I only see and bleed from ONE bleeder down there. Is there another???

 

[jfeagins]

Only one bleeder on the clutch line that I know of, at least that's the way my 85 is set up. I used to have this same problem til I found out how to release that dratted little bubble at the banjo bolt.

Traditionally, I bleed both clutch and brake lines every spring. Have been doing it since I bought my max back in 1985. My problem of a bubble would usually first present itself on or near the first day of spring (after bleeding each year) when the temps first hit near 80. My theory, for whatever reason, was that all the tiny, tiny little bubbles that get trapped into the fresh fluid during a spring bleed would be able to coelesce into a large enough bubble to cause grief when the fluid temps get warmer, and viscosity gets thinner etc. Anyway, that was my theory and I am sticking to it. lol. Also, I pay greater detail to the fresh fluid during my spring bleeds, and try not to allow it to become stirred up when pouring in the new, in addition to paying greater detail to NOT allowing the master reservoir level to get down anywhere near too low before topping off as I bleed the old for the new. Hasn't happened to me again now for a few years.

 

[Triumph1050]

Makes sense... thanks

 

[Fire-medic]

I think concensus among members is that while a mityvac works quickly & well for brakes, a syringe on the slave cyl. bleeder and flushing fluid up from there will usually work better to 'bleed' the clutch system. When changing the clutch fluid, I usually just use the mityvac to empty the master cylinder reservior ("Horrors! The plunger holes in the master cylinder floor are uncovered by fluid!") and then just push the fluid up to fill the master cyl w/residual fluid from the clutch line, and keep doing that until the fluid is clean.

The end-result is a firm, hard clutch, w/resistance just-off the initial clutch lever pull, and maximum slave cylinder piston movement to ensure full clutch diaphragm spring release.

 

[Triumph1050]

I have never tried it reversed I'm going to go try that right now.... Even though I do have a functioning clutch today it could be better.

Looks like I can reverse the ports on the mityvac to pressurize...or go to a pet store or ranch supply store to get a large syringe.

 

[jfeagins]

I don't think Mityvacs push.


I use my hand vac pump (not a Mityvac brand) to empty the darkened/dirty DOT out of my reserviors each year too. But I don't attempt to vac the new fluid down through the system, nor use a syringe to push the old up and out either. I just bleed the old fashioned way by s.l.o.w.l.y pulling the levers while opening the bleeder and letting the old run through a clear tubing and into an old fluid bottle.

I'm just extremely careful while I got the reservior empty to not budge the lever any so's to keep any air from going inside the master cylinder etc.

I likes to refill new fluid up to the middle of the sight glass window while the bars are positioned pointing the front end straight forward, and with the bike on center stand (or upright on the lift...depending on bike I'm working on)

 

[Fire-medic]

Yes, centrifugal bleeding will work, you don't even need to do anything, just open the bleeder and keep the master cyl full, gravity will pull the fluid through, slowly.

The reverse-bleed is much quicker, of-course.

 

[Triumph1050]

thanks looks like I got some better options to try out

 

[Triumph1050]

I think concensus among members is that while a mityvac works quickly & well for brakes, a syringe on the slave cyl. bleeder and flushing fluid up from there will usually work better to 'bleed' the clutch system. When changing the clutch fluid, I usually just use the mityvac to empty the master cylinder reservior ("Horrors! The plunger holes in the master cylinder floor are uncovered by fluid!") and then just push the fluid up to fill the master cyl w/residual fluid from the clutch line, and keep doing that until the fluid is clean.

The end-result is a firm, hard clutch, w/resistance just-off the initial clutch lever pull, and maximum slave cylinder piston movement to ensure full clutch diaphragm spring release.

Well this is exactly what I ended up doing....even down to using my Mityvac to keep sucking the fluid out of the master as I forced fluid in thru the slave bleeder.

I was careful when refilling my large syringe a few times to not let any air into the short tubing Im pretty sure I didn't force any air into the line only fluid. I closed the bleeder valve while still pushing the syringe plunger so Im pretty sure I didn't introduce any new air.

The last syringe full that I did pretty much topped off the master so I put the cover on and was done.

My clutch pull is pretty much the same as it was before I started I believe that either I need a new master cylinder or this is just as firm as this clutch is going to get. Id say it's about 75 to 80% firmness compared to what I think it should be. Its decent and rideable but by no means a hard pull.