What is "clutch drag"??

Post by **KDXGarage** » 03:13 am Oct 01 2005

What does "clutch drag" mean?? Why would a lighter oil be used to prevent "clutch drag"??

Thanks.

m0rie · Post by **m0rie** » 11:34 am Oct 01 2005

I'd think clutch drag would be the clutch not fully dis-engaging when the clutch is pulled in.

skipro3 · Post by **skipro3** » 12:07 pm Oct 01 2005

I'm going to assume you know how the KDX clutch works and have taken it apart a few times. If not, then I hope this still helps.

Clutches work on a friction principal. Alternating discs, some with brake pad-like material are sandwitching steel or aluminum discs. The ones with the brake like material are called friction plates and have tabs that engage the outer clutch basket that they fit in. The steel or aluminum plates are notched on the inside edge and egage the inner clutch hub. The hub is connected to the rear wheel via the transmission and chain. The basket is connected to the crank and motor's top-end. Springs compress the friction plates to the steel plates enough that the motor can drive the rear wheel. The clutch spring tension can be overridden by the clutch lever which counters the springs tension holding the plates together. Oil is used to lubricate and cool the clutch because the slipping action generates heat. Oil with friction modifiers are too slippery and the clutch springs are inadiquate to hold the plates tight enough together to transfer power from the motor to the transmission. When the assembley used to engage the clutch is out of adjustment and won't overcome enough of the spring tension, then the plates are still partly in contact and the clutch "drags" one set of plates over the other. This results in a creeping of the motor's power into the transmission and the bike can move forward or the motor stall out. Oil viscosity is important in clutch drag as well because even with a correctly adjusted clutch mechanisim, where the plates are fully disengaged from each other, they are still spinning through oil. This oil is like a current and will pull the clutch plates along. Think about news videos of a river where a mud flow has occured. During normal water flows, things in the river stay stationary. But when the water is thickened with mud, objects in the river's current are now swept away. Same with the cltuch plates and oil. A thick oil will move plates that would not normally move with a lighter oil.

Post by **fuzzy** » 12:15 pm Oct 01 2005

Clutch drag is an integral feature of the KDX tranny.

Post by **KDXGarage** » 12:29 pm Oct 01 2005

Thanks for the information, kind sirs. skipro3, thank you for your explanation! I never had any clutch problems with my '87 or '94, so I never had to learn much about the clutch. Though my post was based on a comment I saw in a Kawasaki service bulletin, your comments apply to my 1991 KDX250.

Are you saying that when I pull in the clutch lever, the friction plates keep spinning, but the metal plates coast to a stop? When I let out the clutch, the metal plates start spinning again?

While test riding the bike, I stalled it. I was in first gear, and I did not put it in neutral before kickstarting it. I just pulled in the clutch lever and kickstarted it. When the engine cranked, the bike crept forward. I let the clutch lever out, then pulled it in again and revved it a little. It barely crept forward this time. I did it a couple times more just to check it. It was maybe half as bad as when I kickstarted it. skipro3, can you further explain how the clutch action is happening in that situation? I took the pressure plate and plates out of the basket. The friction plates do not look damaged, but I have not dried the oil off them and examined them. I saw some plates from a Yamaha TT-R125 that had been super clutch abused and the plates were warped, streaky and glazed off/over. Mine don't look like that, as far as I can currently tell. The metal plates (aluminum?) look good. The basket finger edges are somewhat notchy, but not as bad as some I have seen pictures of on the Internet. I plan to flat file them just a little bit. A new basket is $225 or $250, with no Hinson or other aftermarket option.

Thanks again for the information. It feels like Clutch 101 and class is in session.

KDXer · Post by **KDXer** » 12:36 pm Oct 01 2005

Has it got something to do with the plates sticking together when it stalls ?? I dunno really, I'm just guessing.

C'mon Mr Skipro schools in...

Post by **KDXGarage** » 12:42 pm Oct 01 2005

I am wondering how the little notches in the basket affect it. Shh! Here comes the professor!

skipro3 · Post by **skipro3** » 04:03 pm Oct 01 2005

Jason wrote:
Are you saying that when I pull in the clutch lever, the friction plates keep spinning, but the metal plates coast to a stop? When I let out the clutch, the metal plates start spinning again?

While test riding the bike, I stalled it. I was in first gear, and I did not put it in neutral before kickstarting it. I just pulled in the clutch lever and kickstarted it. When the engine cranked, the bike crept forward. I let the clutch lever out, then pulled it in again and revved it a little. It barely crept forward this time. I did it a couple times more just to check it. It was maybe half as bad as when I kickstarted it. skipro3, can you further explain how the clutch action is happening in that situation? I took the pressure plate and plates out of the basket. The friction plates do not look damaged, but I have not dried the oil off them and examined them. I saw some plates from a Yamaha TT-R125 that had been super clutch abused and the plates were warped, streaky and glazed off/over. Mine don't look like that, as far as I can currently tell. The metal plates (aluminum?) look good. The basket finger edges are somewhat notchy, but not as bad as some I have seen pictures of on the Internet. I plan to flat file them just a little bit. A new basket is $225 or $250, with no Hinson or other aftermarket option.

Thanks again for the information. It feels like Clutch 101 and class is in session.

O.K. Let's see if I answer all the questions:
Q: Are you saying that when I pull in the clutch lever, the friction plates keep spinning, but the metal plates coast to a stop?

A: Mostly true. The metal plates will coast to a stop if the bike is in gear and coasts to a stop. Remember: Those steel plates are tabbed to the hub and the hub is in direct connection to the tranny. If you pull the clutch lever in and lock the rear wheel, then the steel plates likewise will stop instantly. Some bikes even stall doing this if the clutch lever is out of adustment. If the bike is in neutral, the oil, moving around by the friction plates will usually spin the steel plates and hub. Then, when you nudge the shifter into gear, you will feel and sometimes hear a thunk as the plates start to spin and not spin in relation to each other. You may even hear the engine RPM drop with the drag as well.

Q: When I let out the clutch, the metal plates start spinning again?

A: Yes. And if you let out the clutch only part way, then they spin at an RPM less than the friction plates. That's called slipping your clutch. By careful control of your clutchlever, you can keep the engine RPM's in the powerband and control your speed. For example: A hill climb and your bike starts to load down. You slip the clutch by pulling in on the lever part way, allowing the motor to build RPM's and more power but at the cost of rear wheel speed. That gives your more power but at a lower speed.

Q: Test ride stall, restart in gear w/ noticeable drag, stop and start again in gear a couple times, revved motor and drag is reduced. Why?

A: What I think happens is the plates are held together by a vacuume. You said you removed the plates. I bet it wasn't that easy, eh? They are usually pretty tight fitting with a suction lock between plates from the oil. With the plates out of the clutch but still oiled up, try seperating them by lifting the top plate straight up. It won't go. It sticks!! Vaccume is holding it to the other plate. It will slip across and you can slide the two plates apart that way though. That suction is like a suction cup. A suction cup, wetted and applied to a glass window will slip and slide quite easily. But try and pull it away from the glass and it's stuck. Same with the clutch plates. They should slip across each other, but if pulled apart, like when the clutch lever is pulled in, and you are trying to seperate them, they will hold on tight to each other due to the vacuume being created.
Other causes are plates warped, friction materials worn unevenly or damaged, notched basket. Contamination in the oil is a biggie. Anything in the oil that could cause one plate to drag against the other will be noticed. You may have noticed I skipped over the notched basket situation. I have no experiance with a notched basket so I've never esperianced what that might feel like.

If you are in the market for a new clutch basket, then keep your eye on eBay. Also check buykawasaki.com and see what other models use the same basket.

And if you want to get rid of all clutch creep and poor performance, send your clutch to Garry at EFM. I feel like a preacher hounding his congregation, but I tell you; that auto clutch has given me more riding pleasure and performance than all the other mods put together. If I only had one mod to do or had to choose between the autoclutch and all the other mods ever, I'd choose the auto clutch hands down. That's how much I enjoy riding with it.
A test bike is sitting in my garage for anyone wanting to come out to California!
O.K. that's the end of my autoclutch sermon (for today, anyway)

skipro3 · Post by **skipro3** » 04:10 pm Oct 01 2005

Back to my vaccume senario:

As a clutch spins, the oil is flung away from the space between the plates. Like a suction cup to a window, when the water used to initiate the suction dries up, the cup won't slide across the glass anymore. Your clutch plates are also drying up just a little and there's not as much oil between the plates to allow proper slipping. With the EFM auto clutch, Garry drills several holes in the hub to allow oil to flow in between the plates. And it does work. I start my bike in any gear any time and there is no drag. I push it around in the garage in any gear and I can't tell the difference between in gear or neutral.

skipro3 · Post by **skipro3** » 04:16 pm Oct 01 2005

Oh yea,

There's lots of photos of my clutch in the gallery in their own album. Many of these photos will help anyone reading this understand what the parts look like and how they fit together.

Post by **KDXGarage** » 05:33 pm Oct 01 2005

Thank you again for all the infromation!! It sounds like the metal plates are tied to the output shaft and the friction plates are tied to the input shaft. That helps to make a better picture.

The plates did have suction to each other when I pulled out the stack.

I am going to clean all of them, then check them out.

Unfortuantely, the basket is 1991 - 1994 KDX250 only.

I will keep an eye out, though.

Thanks again!

Jason

canyncarvr · Post by **canyncarvr** » 01:58 am Oct 03 2005

No reason to assume the clutch 'travel' in the EFM setup is the same as the OEM lever job. That may be part of why the EFM'd bike is easy to push in or out of gear.

Also, note that the EFM clutch 'sits' enaged all the time (plates loose). It only hooks up under power. An OEM clutch is opposite..the plates are stuck all the time IT is sitting around.

Thus, they tend to STAY stuck, even when you engage the clutch (pull the lever).

You won't be pushing an OEM clutched KDX around much engine off, in gear and clutch engaged. Not easily anyway.

I wouldn't want aluminum plates in my clutch. IMO and all that.

DRAW file those hub fingers. You don't want to leave any flashing hanging around. At least bother to ensure and flash is gone.

Make sure you have the clutch assembled to spec...with/without washers under the bearing to give the acutator lever the correct º of movement. It's in the book!

Post by **KDXGarage** » 02:23 am Oct 03 2005

stay stuck...stay stuck...hmmm

I am curious to see how a good cleaning and fresh oil will affect it.

What exactly does "draw file" mean?

What bearing are you talking about??

skipro3 · Post by **skipro3** » 10:24 am Oct 03 2005

Good points carvr.

m0rie · Post by **m0rie** » 10:43 am Oct 03 2005

canyncarvr wrote:only
You won't be pushing an OEM clutched KDX around much engine off, in gear and clutch engaged. Not easily anyway.

Make sure you have the clutch assembled to spec...with/without washers under the bearing to give the acutator lever the correct º of movement. It's in the book!

I've wondered about the clutch in, engine off, in gear, no push bit. My E series KDX doesn't have that problem. I think you even remarked about about being able to push it in gear while we were @ Prospect. I've seen H series KDX's have issues with moving the bike in gear. My sisters 220 and your 200 both had that "feature". Is this just a H series problem?

Jason - Under the clutch lever there is a post that come out of the center of the clutch. You can remove that post and place a washer(s) under it to change the activation angle.

-Maurice

canyncarvr · Post by **canyncarvr** » 11:04 am Oct 03 2005

Bearing: The throwout bearing.

Draw file: A matter of movement. Instead of pushing the file 'in' toward the center of the basket, draw it 'out', away from the basket. That will leave the ragged edge left over as a result of the filing easier to get to. That 'edge' depends on materials used and the quality of the file...but you will likely have a bit of flashing left over in spots.

My 'no push' comments were in regard to an 'H' model. Maybe the 'E' has more travel someplace....either in the linkage or clutch innards.

A 'good cleaning' may indeed effect it..and it may be short term. Servicing a clutch commonly includes abrading the flat plates (not friction). That 'resurfacing' will effect the 'stick' part.

...for awhile.

Take two pieces of wet window screen, place them together and you won't get much sticking going on. Do the same with a couple pieces of glass...different issue.

...an exaggeration to make the point.

Post by **KDXGarage** » 01:47 pm Oct 03 2005

m0rie, thanks, I will check the buykawasaki diagrams.

I will pull the file to me. Thanks for the tip. I am going to order one of those Motion Pro clutch holding tools and take it out of the engine before I start filing it. I don't want the shavings (flash) to get in the engine.

canyncarvr, sorry to throw more letters at you, but if you didn't catch it, all these clutch comments as it relates to my bike is for the "D", not the "E". It's a 1991 KDX250-D1, with the clutch actuation like a KX250, where the cable goes over to the left (behind the stator and rotor cover), then a long rod goes through the engine to the clutch on the right side.

Thanks.

skipro3 · Post by **skipro3** » 02:46 pm Oct 03 2005

Carvr's reference to screening and glass is exactly the issue I think. I notice that on my KDX metal (steel) plates that they are smooth finished on both sides. The KX plates are modified with small grooves. It looks like those graphics you put on gas tanks with the little slits in them. These are used to break up the suction effect I believe. I wonder if KX plates would fit a KDX or if any after market plates have these vaccume breaking little slits. The slits are only surface and do not go all the way through the plate BTW.

Post by **KDXGarage** » 02:54 pm Oct 03 2005

My KDX250 metal plates have some little dimples in them.

skipro3 · Post by **skipro3** » 06:08 pm Oct 03 2005

I bet that's the reason you never had a problem. Would your plates fit a new model H motor?

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What is "clutch drag"??

What is "clutch drag"??