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Proper clutch thickness measurement - used clutch looks toast


Trobinson

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I just got a used clutch asssy (springs, plates, clutch disk, flywheel) and the guy I bought it from (along with transmission from a '99 R1100RT) said it was 5.1mm. In doing some research it looks like the measurement is done across both discs and while this one does measure ~5mm it looks worn out to me (see pics).

 

Clutch disc

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I just got a used clutch asssy (springs, plates, clutch disk, flywheel) and the guy I bought it from (along with transmission from a '99 R1100RT) said it was 5.1mm. If I've read the BMW manual correctly this measurement is supposed to be done from the rivet head to the disc surface and not from one side to the other. Is this correct? The disc I have looks worn out to me (see pics).

 

 

Afternoon Trobinson

 

Not exactly, you do measure AT the rivets (due to rivet retention that is usually the thinnest place) but the measurement is total clutch disk thickness at the rivets with the caliper tips held somewhat tight to the disk surface with your fingers.

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Thanks DR, I just found that in some other thread I found. Does it look ok as far as the pics? I haven't measured the one on the bike yet, likely in a couple of weeks, so I don't know the condition of that one although engagement is fine.

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Thanks DR, I just found that in some other thread I found. Does it look ok as far as the pics? I haven't measured the one on the bike yet, likely in a couple of weeks, so I don't know the condition of that one although engagement is fine.

 

Evening Trobinson

 

It looks OK but I'm on a shop computer that has the resolution of an Etch-A-Sketch so don't put too much stock in that observation.

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Well, I re-measured after getting new batteries for the micrometer and it is 5.08 - 5.1mm and ~.02" from the rivet head to surface so it's well within spec. If I need it I'll use it. Thanks for the input.

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Replace the cage bolts and the lock washers when you install it. Once you put the cage and friction plate back on, check your clutch play and set it before installing the drive shaft housing. 12 mm on the thumb screw and 7mm gap to pressure between the lever and its stop on the handlebars.

 

If you squeeze completely and cannot get tension on the cable, when the thumbscrew is 12 mm from its base there is an adjustment on the back side of the transmission. (real easy to get to before the drive shaft is back on...real difficult to do without a special tool if after assembly.

 

 

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Per my previous adventures in R1100 transmission/clutch land.......a new BMW clutch disk measures about 6mm. The one I replaced was wearing into the rivets at about 5mm after 101k miles of use. BMW's minimum spec is 4.5mm. Take all of that for what its worth.

 

Replacing a clutch/transmission on these bikes is not difficult, but it is a decent amount of work. Saying that, I wouldn't bother with a used clutch disk. The last thing you would want to do is tear the bike in half again after 30k miles when a new one should last 100K+.

 

I don't know what you are planning, but here is a link to what I found when the clutch started slipping in my old RT

LINK

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Even if the cage surface looks smooth, take a metal ruler across the entire diameter and you will see the inside edge has a large gap. New ones have a very slight bevel to the center but not as large as one that has seen 100K. Using the same cage can also greatly shorten the life of the friction plate and is recommended to replace both. As Oopezo said...not difficult but a lot of work to get in there. Better to start fresh.

 

Depending on how many miles your bike has on it, you may want to opt for the oil proof clutch friction plate in case one of the seals begin to weep in the rear of the engine or the front of the transmission. They are not cheap....$260 for the plate alone.

 

I haven't seen anything on the forum as to how people like them or to their longevity.

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Even if the cage surface looks smooth, take a metal ruler across the entire diameter and you will see the inside edge has a large gap. New ones have a very slight bevel to the center but not as large as one that has seen 100K. Using the same cage can also greatly shorten the life of the friction plate and is recommended to replace both. As Oopezo said...not difficult but a lot of work to get in there. Better to start fresh.

 

Depending on how many miles your bike has on it, you may want to opt for the oil proof clutch friction plate in case one of the seals begin to weep in the rear of the engine or the front of the transmission. They are not cheap....$260 for the plate alone.

 

I haven't seen anything on the forum as to how people like them or to their longevity.

 

Morning Rx_Mich

 

I have removed 2 "oil resistant clutch friction plates" from bikes of friends as they couldn't stand the poor chattery (sp) launch characteristics on those clutch disks. In both cases I'm not sure who the supplier was so they could have both been from the same supplier or from different suppliers.

 

I don't know if they are all like that but so far I haven't talked to anyone that is real happy with the oil resistant clutch disks in the solid-centered-disk BMW applications).

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Thanks for all the responses. I have done the clutch adjustment so I'm very familiar with that and do plan on setting that up before putting anything else on.

 

As for replacing the clutch my plan is to do so only if the splines or disc currently on the bike are worn enough to warrant it. Engagement is fine right now and most of the miles I've put on the bike have been highway (used to have a 140 mile commute) so the wear may be less than expected. I'll be taking pics during the teardown so we'll see.

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