Clutch engagement point - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 14 (permalink) Old 10-11-2011, 09:48 PM Thread Starter
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Clutch engagement point

I bought my '03 RC in July and have performed most of the basic maintenance tasks on it. Since I bought it, the clutch felt like it was seriously worn, as the engagement point was basically right with the lever all the way released. I did a fluid replacement and bleed for good measure, with no improvement (wouldn't expect it to).

I replaced the entire clutch pack and springs recently, and bled it again, but the engagement point is the same! I've got to have the lever about 2mm from fully released to get some bite. I tried adjusting the lever, to no avail. Anybody got any ideas? Is the master cylinder toast? I'm at a loss.

Thanks in advance.

2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
2002 ZX-7R (sold)
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post #2 of 14 (permalink) Old 10-12-2011, 09:50 AM
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Hydraulic clutches have no free-play adjustment. The lever has very little travel from fully engaged to fully disengage. If you consider the total lever travel (approx. 4 at lever end), the first -1 is lever free play, next can be considered slippage and the last 2 fully disengaged.

Most problems are slippage caused by worn discs, springs or piston sticking, or creeping caused by air in system, warped plates, and fluid or oil problems. Corrosion is also an issue on systems that are neglected.
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post #3 of 14 (permalink) Old 10-12-2011, 10:03 AM Thread Starter
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The rubber boot for the master cylinder piston pin is torn. So there could be some damage there. What's the chances that the spring in the master cylinder has been compressed over its life? Is that a typical wear item? Is it worth it to tear down to master cylinder, or just replace the assembly? I've found them on eBay and rc51parts for between 80 and 100 dollars.

2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
2002 ZX-7R (sold)
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post #4 of 14 (permalink) Old 10-12-2011, 10:30 AM Thread Starter
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Hydraulic clutches have no free-play adjustment. The lever has very little travel from fully engaged to fully disengage. If you consider the total lever travel (approx. 4 at lever end), the first -1 is lever free play, next can be considered slippage and the last 2 fully disengaged.

Most problems are slippage caused by worn discs, springs or piston sticking, or creeping caused by air in system, warped plates, and fluid or oil problems. Corrosion is also an issue on systems that are neglected.
I understand everything you said, and I've applied most of that troubleshooting already. I own a Ducati as well, so I understand how hydraulic clutches work and feel.

I assumed the reason for the engagement point being so far out was worn plates and possibly worn springs, so I replaced the pack and springs. The old plates were negligibly close to the wear limit, and the free length of the springs was slightly longer than the wear limit. I had all the parts in the kit, and everything under the cover is brand new. The oil was changed less than 1000 miles prior to the clutch, and I soaked the new friction plates in the same grade and brand of oil prior to installing them.

If there was air in the system, I would be unable to disengage the clutch. I'd have to pull the lever further in than the bar allows to stop drive to the rear wheel. That is the opposite of my symptom.

2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
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post #5 of 14 (permalink) Old 10-12-2011, 11:12 AM
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I went completely thru my master and slave cylinder recently. I did replace the spring in both the master and slave. Some people argue that springs don't wear out. I don't know, but after the rebuild, my engagement and disengagement were right in the sweet-spot again.The only exception is when the weather is hovering around 100 degrees, then my handle comes out further to engage the clutch, almost to the end like you said. But only when the bike is around 210-220 degrees for prolonged times.

So my opinion is change the springs when you change the cups/seals and o-rings.

John, 2000 RC51 #000100

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post #6 of 14 (permalink) Old 10-12-2011, 11:44 AM
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So my opinion is change the springs when you change the cups/seals and o-rings.
/\ Good advice.

The rubber boot is a dust cover.

The spring does not have a spec limit (but I agree with jondog9), but the piston/piston cups do.
Piston re-build kits are less than $60.00 and include the spring.
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post #7 of 14 (permalink) Old 10-12-2011, 01:56 PM Thread Starter
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Alright, so assembly number 3 should be all I need for the master cylinder, right? I'll probably order the O-rings for the reservoir as well (28 and 29 in the figure).



For the slave cylinder, I just need 6, 8, and 9, correct? Should I replace the pushrod oil seal (part 13) while I'm in there?

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2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
2002 ZX-7R (sold)
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post #8 of 14 (permalink) Old 10-12-2011, 11:50 PM
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Alright, so assembly number 3 should be all I need for the master cylinder, right? I'll probably order the O-rings for the reservoir as well (28 and 29 in the figure).



For the slave cylinder, I just need 6, 8, and 9, correct? Should I replace the pushrod oil seal (part 13) while I'm in there?

That's exactly it! And do replace the pushrod seal while you're in that deep. I did. You'll get a new dustboot with that kit in 3 for the master. Dont be surprised if the new cups look too small. It freaked me out a little how over sized my old stuff got. That reminds me, I'd say get a new diaphram for the clutch resevior too. That goes right under the cap.

John, 2000 RC51 #000100

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post #9 of 14 (permalink) Old 10-13-2011, 09:08 AM Thread Starter
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One other thing I didn't put in my first list I just wanted to add for anybody who ends up finding this thread later. Don't forget the copper crush washers for your banjo fittings. They're cropped out of my screenshot for the master cylinder, but that's the page of the parts fiche they're under.

What does the diaphragm in the reservoir cap do? Seal out moisture? Also, do you mean the "diaphragm" or the "diaphragm plate"? See the parts fiche here. Part 5, part 8, or both? Mine seemed fine when I bled it the other weekend.

2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
2002 ZX-7R (sold)

Last edited by Crarrs; 10-13-2011 at 09:57 AM.
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post #10 of 14 (permalink) Old 10-13-2011, 05:10 PM
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One other thing I didn't put in my first list I just wanted to add for anybody who ends up finding this thread later. Don't forget the copper crush washers for your banjo fittings. They're cropped out of my screenshot for the master cylinder, but that's the page of the parts fiche they're under.

What does the diaphragm in the reservoir cap do? Seal out moisture? Also, do you mean the "diaphragm" or the "diaphragm plate"? See the parts fiche here. Part 5, part 8, or both? Mine seemed fine when I bled it the other weekend.
Ditto on the crush washers for both banjo bolts. Good call.
I re-use mine a couple times then replace them all.

Diaphram. Part 5. seals out moisture, and keeps the system closed, so no new air can enter the resevoir as the fluid level drops over time. Dont overfill your res, you probably already know that.
I use indy oem. much better prices.
http://www.indyoem.com/fiche_section...2001&fveh=3620

John, 2000 RC51 #000100

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