Exploring clutch drag...... - Page 2 - K-Bikes.com - Excellence in Motion
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post #11 of 14 (permalink) Old Sep 24th, 2019, 7:43 am Thread Starter
Join Date: Aug 2017
Posts: 22

I agree with you, ‘Production tolerance variations could be significant.’ A collection of tolerances on one side of the range could be expressed one way on this bike and another bikes ‘DNA’ not expressed at all. It helps explain the different range of experience members have. There is also personal perception, fingernails on the black board makes me cringe. For another it could be just background noise.

I have kept that bellville washer on the hub. It is an active separation feature. As I think I mentioned somewhere, the difference between the unsprung bellville washer and it’s washer and the friction plate height is very close, I won’t say exact anymore, to the .125mm for each space. When the pressure plate is disengaged, this first plate, at the hub, has to wait its turn to separate. That bellville washer gives a little push to the rest of the plates. I have wondered about a clutch where each pair of plates had a bellville washer. Little dictators, nothing to see move along. I agree more space on the hub for the plates to shift would be where I would start.

I have to think those that designed this clutch had something in mind. The characteristics they were after resulted in some trade offs. This is pure speculation, this bike was designed to be fast through the gears. 2.8 seconds! Is the small amount the clutch lever has to be pulled to initiate a gear change, one of those trade offs? Speed over clunk.

I initially spent weeks trying different ways to add oil. Lack of oil has been the gold standard. I could not change the clunk in any way by trying to increase the oil. This embedded idea of not enough oil I think comes from the wear seen on the hub and pressure plate. I’m starting to think that the ‘clunk’ itself adds to the wear. This rotating mass comes to a sudden stop. Seems there is some sliding of the plates under pressure until they break. One of Patrique Hofmann’s early videos shows the clutch he has removed from his bike. The whole thing was bone dry. The hub and first plate as well as the friction against the pressure plate were worn bare. But all the middle plates looked fine. He remarks that he is surprised it didn’t blow up. There were a few issues with oil nozzle and oil holes. For me this pointed to where the amount of oil was important. The middle of the clutch pack needed just enough oil that it’s shear strength is easily overcome. (Shear strength, that was the word I was looking for. Fluid coupling as a term is more all encompassing. Shear strength is more specific.). At the hub and at the pressure plate is where oil is the most critical.
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post #12 of 14 (permalink) Old Sep 24th, 2019, 10:01 am Thread Starter
Join Date: Aug 2017
Posts: 22
Something of note that has wrinkled my forehead. A ways into the modifications I was trying, I noted that as the oil temperature went up, the clunk went up. I came to understand it takes about 20 minutes of riding to get the oil temperature up to its stable operating temperature. General riding, not city not highway. So why no clunk while heating up but returning when hot? My only thought has been to do with the small oil hole size I’ve settled on. Maybe the higher oil viscosity when not up to temperature can’t get through those small holes in enough volume to create drag. But when the oil is hot it’s almost water like and easily flows throughout the clutch. I don’t really know, but it fooled me into thinking I’d got it! Then when I went for a general ride there was my unwanted companion, the clunk
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post #13 of 14 (permalink) Old Sep 24th, 2019, 10:59 am
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Join Date: Apr 2017
Posts: 52
Well, there isn't much that i can add to the clunk problem besides having installed a K1300 driveshaft, which has improved the clunk a little. And having highly modified the clutch pin on a lathe to increase oil flow to the clutch..... my clunk has become acceptable. I also dont have the beville spring, but i do have a new lamellar package on shelf with one in it when necessary.......
I did notice though, that the clunk reduced significantly after replacing the caked/pasted up first clutch plate from my video.
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post #14 of 14 (permalink) Old Sep 24th, 2019, 11:58 am Thread Starter
Join Date: Aug 2017
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I wonder if the belleville spring allows better flushing of that friction plate? The elbow room it provides might open it up to easier flushing.
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