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Clutch Slipping

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Kelsen

Kelsen

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Got on my Bandit for the first time in a couple of months (just too **** hot in Alabama lately). After the first half-mile, any acceleration more than very gentle increases the RPMs without increasing my road speed. In a few seconds, it catches up, but the clutch seems to be slipping regularly.

The manual doesn't give much information on this. Can anyone tell me what kind of work I will need to do to test/fix this problem?


Dave Kelsen
 
Open up the clutch and measure the length of the clutch springs and compare to the speds in a shop manual. They 'creep' over time and thus can't fully push the plates together. I guess it could also be worn plates or discs in there, but if it went from fine to slipping quickly (while just sitting in a hot garage, etc), then I'd bet on the springs.
 
Did you recently change oil? Energy saving oil will cause that, 28K seems too early to have worn out clutch parts.
Smoky
 
I did not recently change oil. and I use the same brand and weight of oil each time I change it (Rotella T-5, I think).

I agree about that being early for worn clutch parts; and I do not use the transmission for slowing, or ride the clutch at all. I don't even sit at a light in gear with the clutch lever pulled in.
 
10 year old springs that are partially compressed all the time are gonna creep. It only takes a couple millimeters for their effectiveness to decline. If I were you, I'd buy replacements before pulling the clutch cover - just so I could have a fix in place same-day. Note: I know exactly nothing about bandits, so feel free to ignore me :)
 
You may want to try bleeding the the Clutch System first.
Air in the system can cause slippage. Also a bad slave cylinder, or gummed up rod.
The clutches are plenty strong, hence drag racers like Suzuki’s so much....and the power ;)
 
Jeff S said:
10 year old springs that are partially compressed all the time are gonna creep. It only takes a couple millimeters for their effectiveness to decline. If I were you, I'd buy replacements before pulling the clutch cover - just so I could have a fix in place same-day. Note: I know exactly nothing about bandits, so feel free to ignore me :)
Click to expand...
I know this will be a tire or Oil thread like comment, but there is a ton of actual research and data to support my statement vice oil and tire beliefs :giveup:

Springs 'wear" or fail to be at the designed spec though cycles or heat above design range. Its been shown time and time again, age nor time compressed do not materially effect the spring unless the spring was compressed or stretched above teh design range.

That said you have a good idea and point to check...10 year old bike the clutch springs likely do have significant number of movement cycles on them, so they may very well be shorter free length then the spec calls for.

Creep as I understand it from materials science course Iv taken, (nope, Im not an engineer so only know what I think I know, Ive never had to prove it to a thesis review board) Creep, as mentioned mostly affects materials at or above ~0.4x their melting point. So not likely to be an effect issue with a properly designed and produced clutch spring.

To the OP, Start with Bleed and back bleed the clutch hyd system, Air in a clutch system like the bandit has can cause either clutch to not engage or disengage.
If no luck there..

Measure the spring free length and compare to the OEM spec.
Measure the thickness of the drive and driven disks and compare to the OEM spec.
Check for flatness of both drive and driven disks.
Inspect the clutch pressure plate for signs of wear, which would lesson clamp load when assembled.
Inspect the clutch basket fingers for grooving that might cause clutch disks to hang up.
Keep in mind the bike uses three different designs of drive plates, and they can be mixed up if not careful..

Drive plate I.D. Clutch facing “D”
No.1 127 mm (5.0 in) 48 pcs
No.2 135 mm (5.3 in) 60 pcs
No.3 127 mm (5.0 in) 60 pcs

And there are two sizes of driven plate
Driven plate Thickness
No.1 2.0 mm (0.08 in)
No.2 2.3 mm (0.09 in)

Item Standard Limit
Clutch drive plate thickness No.1, 2, 3 3.72 – 3.88 (0.146 – 0.153) 3.42 (0.135)
Clutch drive plate claw width No.1, 2, 3 13.9 – 14.0 (0.547 – 0.551) 13.1 (0.52)
Clutch driven plate distortion — 0.10 (0.004)
Clutch spring free length 65.0 (2.56) 61.8 (2.43)

"The manual doesn't give much information on this"
Click to expand...

The service manual does, all the above came from the service manual and there is more, troubleshooting steps, procedures, special tools
 
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I've had this on my old Honda's and it's not been the springs. When the bikes sit for a long time, the clutch plates start to stick together. It seems they would get better when they got warm. The fix was to replace the plates or soak them and clean them.

I wonder if one of those miracles in a bottle added to the oil might clean the plates. MMO?

Edit: FYI - I am just tossing this out there cause it's a fairly easy test and repair. Marquez is a mechanic and you would be wise to listen to him.
 
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SL350 said:
I've had this on my old Honda's and it's not been the springs. When the bikes sit for a long time, the clutch plates start to stick together. It seems they would get better when they got warm. The fix was to replace the plates or soak them and clean them.

I wonder if one of those miracles in a bottle added to the oil might clean the plates. MMO?

Edit: FYI - I am just tossing this out there cause it's a fairly easy test and repair. Marquez is a mechanic and you would be wise to listen to him.
Click to expand...

Interesting idea; in my case, the slippage seems to increase as it warms up, although I haven't done enough testing to be really sure of that.

I might look in to some Marvel Mystery Oil. thanks.
 
E.Marquez said:
<interesting stuff deleted>

The service manual does, all the above came from the service manual and there is more, troubleshooting steps, procedures, special tools
Click to expand...

My reference that the service manual doesn't say much about this was to clutch slippage.

The manual contains this:

Clutch slips.
Weakened clutch spring. Replace.
Worn or distorted clutch pressure plate. Replace.
Distorted clutch plate. Replace.

I appreciate what you have said here, and I will try to determine what is causing this. Thanks.
 
Kelsen said:
My reference that the service manual doesn't say much about this was to clutch slippage.

The manual contains this:

Clutch slips.
Weakened clutch spring. Replace.
Worn or distorted clutch pressure plate. Replace.
Distorted clutch plate. Replace.
.
Click to expand...
Well that would be because other than bleeding the clutch, those are the only reasons it is slipping.
The OEM assumes you used OEM parts, only recommended oil, proper tools and procedures.
So the above reasons are it for slipping.

But add in as a variable aftermarket clutch disks and you get to be concerned about the total stack height
Install a new Oberon Slave cylinder (I just did and I'm giddy about it) and then have slipping, well you need to look at that non OEM part
Follow some forum internet advice about removing 4 drive and three driven discs replacing with two wooden blocks and piece of gum wrapper and ....well you get the idea.

Luckily for you,,,it sounds like you have a nice easy diagnosis to work though and you should find definitive observable reasons and thus solutions for your clutch slipping.

As long as you have the proper tools to take accurate measurements with....your golden .
 
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I would agree with much of the above. Having the plates stuck together would not make them slip, quite the opposite actually. Time to buy a gasket and pull it apart.
 
brcol said:
I would agree with much of the above. Having the plates stuck together would not make them slip, quite the opposite actually. Time to buy a gasket and pull it apart.
Click to expand...

In over 55 yrs of riding and working them there motorcycles, Yep!
 
Thanks, guys. Got the springs, was going to do this tomorrow, the 11th, starting with changing the clutch fluid entirely.

But I forgot to order a gasket. I'll still do the fluid tomorrow, and it may solve the problem.


Dave Kelsen
--
2008 Suzuki GSF1200S
 
iv been in and out of a couple bikes many times and have been able to reuse the side cover gaskets, just the luck of the draw though. just be carefull pulling it apart.
 
brcol said:
I would agree with much of the above. Having the plates stuck together would not make them slip, quite the opposite actually. Time to buy a gasket and pull it apart.
Click to expand...

I might not be good at describing what I am talking about but a bit of gunk on the plates will make them stick together while at the same time, not providing the same friction as the disk surface which is a bit like sand paper on mine. That gunk has to be cleaned off or the disk replaced. Only way to tell is to examine the plates.

This is a fairly common condition in the old Hondas I look at.
 
I'm surprised no one has brought this up....Anything restricting the movement of the clutch lever to a fully resting position with almost zero contact with the master cylinder piston will cause this. As the engine warms, and the fluid heats up, it tries to return excess volume to the master cylinder reservoir. A partially restricted piston travel blocks the bleeder hole to the reservoir. So the system has a finite volume. And the expansion makes it act like one finger is slightly pulling in the clutch.

A lack of lever pivot and contact point lubrication will do the same thing by blocking the bleeder hole.

A particle blockage in the bleeder hole does the same thing as well.

On the brake side, I've personally witnessed a friend crash on the track due to a lever installed with the lever adjustment not allowing full piston return. One the clutch, I've seen a crash damaged hand guard restrict lever travel and cause a lockup. We had a brake issue last Mextrek from a hand guard restricting lever travel as well.

In the base case, it is super easy to check...other than looking at the physical lever assembly...just take off the cap on the reservoir. Pump the brake / clutch. If fluid swirls in the reservoir when you release the lever there is no blockage. 1 min check. Easy peasy.
 
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Good tip, Shadman.

Today I changed the fluid, and the problem seems to be alleviated. I'll be sure when I get a chance to take a longer ride, and everything gets to and stays at full operating temperature -- but it happened almost as soon as I left my driveway before, and I rolled around a couple of miles, giving it some sudden throttle, and did not notice the problem, so I think it's solved.

Thanks all for the advice and support. Keep on rollin'!


RFT!!!
Dave Kelsen
 
So, changing the fluid turned out not to solve the problem. I want to learn more before I take off the clutch cover, because to do so, I have to remove my crashguards (Renntec), and I remember what a pain it was to put them on.

Can anyone give me more information about the 4 position rotary switch next to the clutch lever? Can this be related to a possibility of clutch slippage?

Thanks.

RFT!!!
Dave Kelsen
 
I did wind up having to replace the clutch master cylinder; it was not allowing the proper movement of fluid, and the clutch lever was not completely disengaging. All good now.


RFT!!!
Dave Kelsen
 
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