Clutch acting up even after fluid flush and clutch pack replacement

Discussion in '3rd & 4th Generation 1990-1997' started by DrMacDaddy, Aug 17, 2020.

  1. DrMacDaddy

    DrMacDaddy New Member

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    Essentially what's happening, is the clutch is functioning perfectly when the bike if started cold...but once the bike is warmed up to the point where the radiator fan kicks in...the clutch begins to act up. It's almost as if I've pulled in the clutch lever...but I haven't. When I'm riding steady in a gear, like 4th, and give the throttle some acceleration...I see the tach rev up but I do not feel the acceleration via the back wheel. It's as if the engine and transmission are barely connected. If I leave the bike to cool down overnight and fire it up the next morning, the clutch works perfectly until the bike reaches normal operating temperature. The clutch fluid has been replaced with new synthetic DOT 4 brake fluid...and a new clutch pack has been installed....and yet the problem still continues. I see no signs of leakage at either end of the clutch hose, and the fluid level is right where it should be in the reservoir window. The bike starts and runs beautifully, and accelerates strongly when the bike is still cool. The problem always occurs when the fluids are hot. With the plastics off the left side of the bike, I have noticed a section where the clutch hose lies right next to the hot radiator hose. For about an inch, they are literally touching. Could this be heating the clutch fluid to some critical level that it expands...and ends up partially engaging the clutch in the process? If I re-routed the clutch hose, and perhaps wrappyed the radiator hose in thermal exhaust tape, could this keep the clutch fluid cooler...and perhaps stop the problem? Thanks for any help you can provide!!
     
  2. Captain 80s

    Captain 80s Member

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    Sounds like your bleed hole (or both small holes) in the Clutch Master might be plugged, or the M/C needs a rebuild. It's the TINY hole under the little press in "hood". Perhaps when the clutch hyd fluid gets hot, it can't bleed off properly and starts expanding and pushing on the clutch slave cyl?

    Idk... no bad ideas... spitballin'
     
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  3. squirrelman

    squirrelman Member

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    it's important not to fill the mc too full, leaving space for expansion.
     
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  4. Terry Smith

    Terry Smith Member

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    Listen to the Captain, for he speaks the truth!
     
  5. raYzerman

    raYzerman Member

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    Good idea to isolate from heat source, but your reservoir is likely overfilled.
    +1 on checking the bleed hole while you're in there.
     
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  6. DrMacDaddy

    DrMacDaddy New Member

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    Thanks Captain,...and the rest of you jumping into the conversation. Any ideas at all will be appreciated. When I was walking the dog this morning, I thought of the possibility of the master reservoir having too much fluid in it. I will definitely remove some of the fluid giving more room for expansion. I will also look for that bleed hole or holes...and make sure that it/they are not plugged. I'm assuming that your phrase "press in hood" is referring to the rubber diaphragm that is located right underneath the metal cover, and that the bleed hole or holes are located right underneath that. Let's collectively keep our fingers crossed that this works. I will take the bike for a test ride after these 2 steps and let you know how things go. Thanks again for your help!!
     
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  7. Terry Smith

    Terry Smith Member

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    There is a small steel shield that is pressed in, in the floor of the reservoir. If you pick that out, you will see the tiny port in the floor of the reservoir through to the piston bore below, plus the larger fluid intake port. When you activate the lever, you should see a little jet of fluid come up through that port (the shield stops that squirting in your face normally). With the reservoir half full, you should see the disturbance on the liquid surface from the jet. If the jet flow is weak or non-existant, that would indicate a blockage.
     
  8. DrMacDaddy

    DrMacDaddy New Member

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    Ok...feedback time. I removed the clutch reservoir cover, plastic plate and rubber diaphragm. At the bottom of the reservoir, it appeared as if there were 2 holes, but no visible shield. A larger diameter hole closer to the hand grip, and a small hole closer to the clutch fluid hose. I used a hypodermic needle and carefully cleaned out the holes as best I could. I definitely saw some rust-colored debris coming off into the fluid. The needle was connected to a syringe, which I used to suck up the debris along with 2 ml of fluid which I discarded. I could see where the level of fluid in the reservoir had dropped. I reassembled and took the bike for a ride. Unfortunately, the exact same thing happened. The bike clutch worked perfectly until the bike was fully warmed up.
     
  9. squirrelman

    squirrelman Member

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    :eek:

    looks like you proved it's no hydraulic issue.

    how many miles on her ? weak clutch springs ? dija check total thickness of new plate stack ? oem or aftermarket ?
     
    Last edited: Aug 18, 2020
  10. Terry Smith

    Terry Smith Member

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    You might still have a piece of crud in the piston bore/lines that is getting back to the bleed hole when the clutch has been worked a few times. Always do the easy stuff first, I'd suggest you disassemble the master/piston and give the parts a good clean, then flush lots of new fluid through the system and out the slave bleed. Your other option is pulling the engine cover off and pulling the clutch back out to look for a mechanical cause. I know which I'd rather do...
     
  11. DrMacDaddy

    DrMacDaddy New Member

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    Thanks for the feedback. Last night I took another look at the inside of the reservoir, and this time I did see the shield. It was laying in the corner of the reservoir. Does that small chrome clip or shield play any functional role in the clutch mechanism? Could it lying in the corner of the reservoir be causing the problems? I tried pulling the clutch lever in several times, and saw absolutely no disturbance in the fluid itself. That may provide backing to your theory that it's plugged up.
     
  12. Captain 80s

    Captain 80s Member

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    I wouldn't be pulling apart my clutch pack until I was 100% sure my master was working properly.

    It sure seems like yours is not. As Terry stated before, without that hood, the fluid disturbance should be very apparent.

    Even after your fluid "flush" the first time you still had rusty debris come up? Take it apart and clean/rebuild it properly.
     
    Last edited: Aug 19, 2020
  13. raYzerman

    raYzerman Member

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    Listen to the Captain... no fluid splashback is an indication that m/c needs a cleaning. The hood just prevents backsplash as you bleed. As fluid heats up, it can't return to equalize the pressure build-up so instead your slave moves thus partially releasing clutch.
     
  14. Terry Smith

    Terry Smith Member

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    upload_2020-8-20_9-40-51.png
    Sorry about the resolution, diagram is from the Honda common service manual. When you press the clutch lever, the piston assembly moves right to left. Before you start, compensating port isopen between the reservoir and the pressure line and the main intake is open to the non-pressure side of the primary cup. As you press, the compensating port gets closed allowing you to pressurise the system. As you can imagine, as the pisoin starts to move, fluid pressure will push out through the compensating port and hence you get the jet; the only purpose of the shroud is to stop that squirting right out of the reservoir when the cap is not in place during maintenance. The primary cup (piston seal) allows flow one way from the reservoir when the fluid needs to be replenished, so can't release pressure back to the reservoir itself, this has to occur through the compensating port. If that port is clogged, then as the clutch fluid heats up with use and expands, you start to generate pressure even though you are not moving the lever = clutch slip.
     
  15. DrMacDaddy

    DrMacDaddy New Member

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    Thanks for everyone's input. I will definitely have the clutch master cleaned and rebuilt. The kits are not that expensive, and I have a friend who is a very talented mechanic....so I'll ask him for help. I appreciate everyone's help.
     
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  16. Captain 80s

    Captain 80s Member

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    Go at least K&L quality on the kit. Honda OEM is best. Buy the cheap kit and experience our wrath.

    Good luck!
     
  17. COS_VFR

    COS_VFR New Member

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    I found that the hardest part of rebuilding the master cylinder is getting the internal snap ring out. I recommend that you have a quality set of snap ring pliers when you tackle this job. The rest is relatively easy.
     
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  18. DrMacDaddy

    DrMacDaddy New Member

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    My mechanic friend ordered the K&L rebuild kits for both the master cylinder and the slave cylinder. Now we're just waiting for them to show up and for our schedules to align.
     
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  19. zapp916

    zapp916 New Member

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    I had a similar thing happen recently when I attempted to repair the slack in my clutch lever. I made a brass barrel to replace the worn one. This fits into the clutch lever where the push rod is inserted. And while I allowed 2mm free-play, when things warmed up - 5 kms down the road, my clutch started disengaging to the point where I had to take off in 2nd gear to move at a snails pace.

    i took the barrel out drilled it a bit deeper and increased the freeplay by another 1.5 mm. Since then it's been fine.
     
  20. DrMacDaddy

    DrMacDaddy New Member

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    I'm happy to inform everyone helping out on this thread.....that the problem has been fixed. As you successfully diagnosed, the problem was the master cylinder for the clutch. My mechanic ordered and installed both the master and slave kits, as well as thoroughly cleaned out the master reservoir. Apparently, it was quite dirty...and was literally plugged at the bottom. Now that everything is fixed and the bike is running strong, I am going to sell it. If any of you know someone who's in the market for a pristine VFR...here's the link... https://kansascity.craigslist.org/mcy/d/gardner-honda/7189297051.html
    Thanks again for all of your help in resolving this problem. I am so thankful and appreciative for your assistance.
     
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