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Thread: Rebuilding a clutch without special tools.

  1. #1
    Rally Rat
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    Rebuilding a clutch without special tools.

    so I put a 3.00 rear end in, and took it for a test drive. ('It' is a mutant beast, most closely resembling an r90/6 of the mid-70's vintage)

    It liked the new rear end, but the tall gearing is causing the clutch to slip. Or the clutch has started slipping on it's own, take your pick.

    I have the parts to replace it, but I don't have the specialty tooling.

    Any thoughts on getting past this, other than 'buy the special tool'?

  2. #2
    Administrator 20774's Avatar
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    What tool? I had no special tools when I did my clutch. You will need some long metric bolts and nuts to back off the spring pressure.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Superkraut typ181r90's Avatar
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    All you need are long metric bolts/nuts/washers to back off the compression plate/re-compress it. The only special tool involved is the clutch centering tool (I think I got mine from Northwoods Airheads) but I've heard of plenty of people using screwdriver handles to do the same thing, or not using anything at all - honestly whe I used my "my special tool" I also thought that I could have easily used something else instead
    // 1975 BMW R90/6 (cafe'd) // 1957 BMW R60 (in pieces) // 1967 Aermacchi/H-D Sprint 250 SS (custom special) // 1973 VW Type 181 Custom SOLD )

    http://symphonyofshrapnel.blogspot.com

  4. #4
    Rally Rat
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    As I understand it, there are some issues with clutch alignment while re-installing the diaphram spring, pressure plate, and friction disc.

    According to Clymer,(chapter 5, page 208, not sure which printing, but at least post 1981, perhaps 1985?)

    "Do not attempt to reassemble and install the clutch assembly without the clutch-plate centering tool (BMW special part No. 21 6 650)(Figure 32)
    the Alignment of the friction plate to the transmission shaft is very critical. During transmission assembly installation, slides through the friction plate's center splines. If this alignment is not correct, you will not be able to install the transmission assembly."

    That's the part I'm concerned with. without the tool, how does one align the friction plate correctly? I would rather figure this out -before- I take things apart, than have to do it on the fly.

  5. #5
    Administrator 20774's Avatar
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    I've done clutches on all my bikes without "the tool". What I've done is first look at where the clutch disk is before taking it apart...even take measurements from the outside compression ring to specific points on the disk. When putting it back together, replacate those measurements as closely at possible. I try reassemblying a few times and maybe make an adjustment on the disk if necessary. If the transmission won't slide home onto the studs, I put the tranny on as far as it will go and see if I can hook up the clutch cable and actuate the clutch a time or two. Usually I don't have to go that far.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
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    Clutch alignment tool http://www.northwoodsairheads.com/Tools.html is nice to have, but as already mentioned, not utterly critical.

    I have one from years ago, so I use it.
    Ride Safe, Ride Lots

  7. #7
    Registered User melville's Avatar
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    A centering tool can be made quite easily. From the Haynes manual:



    Find a socket that approximates the 20.7mm diameter, and a bit of all thread and some nuts and washers:





    Grind a taper on the end, running both the grinder and the drill so the point is centered:





    Test:



    And success:



    Nothing to it.

  8. #8
    Registered User R100RTurbo's Avatar
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    Quote Originally Posted by 20774 View Post
    I've done clutches on all my bikes without "the tool". What I've done is first look at where the clutch disk is before taking it apart...even take measurements from the outside compression ring to specific points on the disk. When putting it back together, replacate those measurements as closely at possible. I try reassemblying a few times and maybe make an adjustment on the disk if necessary. If the transmission won't slide home onto the studs, I put the tranny on as far as it will go and see if I can hook up the clutch cable and actuate the clutch a time or two. Usually I don't have to go that far.
    +1 with what Kurt said - don't really need the tool although its professional. A bit of care aligning things prior to torque up, and then the ability to relax the disc by having cable connected and releasing clutch during the final slide home of tranny.

  9. #9
    Monza Blue 1974 R90/6
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    Here is another source for the alignment tool and the removal bolts.

    http://www.cycleworks.net/index.php?...cPath=29_33_52

    For sure, the three bolts to release the spring tension are easy self source.

    It's true, you don't "really" need the alignment tool. But, it makes the install much easier.

    I like the above fabrication suggestion. Really nice and I had not seen before.

    Final thought is the other "special tools" you probably need are a micrometer to measure the clutch thickness in a couple of places, a depth gauge to measure the diaphragm spring height, and a rule or other short straight edge to see if the wear surfaces are "cupped".

    Just replacing clutch might not solve slipping problem if the spring is worn.

    Barron

  10. #10
    advrider.com
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    I have serviced probably 10 airhead clutches and a Honda CRX clutch, manuals of which said you need the centering tool.

    I have never used it.

  11. #11
    Curmudgeon nrpetersen's Avatar
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    If you don't have a precision alignment tool, dont snug up the transmission-engine bolts without first releasing the clutch. IOW also assemble the clutch release stuff and be sure the clutch is releasable by trying to rotate things engine-off using the rear wheel. Keep the clutch released while tightening those engine transmission bolts.

    I even started the engine with the transmission slightly loose & then felt between the engine and transmission while re-engaging the clutch to get better alignment. You might feel a little "breathing" between the two (once/revolution) if the clutch disk isn't properly centered.

    What you are trying to do is be sure that in tightening things up, you are not dragging the clutch disk across the flywheel face and bending everything in that part of the drive line. You want the transmission centerline to be exactly aligned with the spinning crankshaft centerline. Otherwise, you might lock in a radial load that will wear your transmission input spline excessively. If the engine and transmission are not aligned perfectly, the clutch hub spine really catches the radial scrubbing every engine revolution.

    This is not a procedure specifically endorsed by others, but it can't hurt and only takes a couple of minutes to do. I'm not sure a precision tool even helps that much. There is a case pilot diameter system that helps, but you can still lock in an alignment error of a couple of thousands. Remember that the crankshaft rotation centerline will move around in the clearance of the rear main bearing. That's one advantage of doing a final tightening with the engine running.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  12. #12
    Administrator 20774's Avatar
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    Quote Originally Posted by nrpetersen View Post
    What you are trying to do is be sure that in tightening things up, you are not dragging the clutch disk across the flywheel face and bending everything in that part of the drive line. You want the transmission centerline to be exactly aligned with the spinning crankshaft centerline. Otherwise, you might lock in a radial load that will wear your transmission input spline excessively. If the engine and transmission are not aligned perfectly, the clutch hub spine really catches the radial scrubbing every engine revolution.
    I suppose this couldn't hurt but it was my understanding that there is no relative movement of the transmission when it is mounted. This is a "trick" suggested by Duane Ausherman on the earlier /2s, but I don't think there is any room for the transmission to move laterally when it is mounted in place. It must be pulled down squarely to the engine...that is easy to see by looking at the mating crack between the two. But side-to-side...I just don't see it. The clutch disk of course aligns itself to the transmission shaft and if the transmission doesn't move laterally with respect to the engine, I don't see the issue.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  13. #13
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    I did mine by eye. The transmission slid into place without any problem. Seems to work fine.

    Chip

  14. #14
    Curmudgeon nrpetersen's Avatar
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    Quote Originally Posted by 20774 View Post
    I suppose this couldn't hurt but it was my understanding that there is no relative movement of the transmission when it is mounted. This is a "trick" suggested by Duane Ausherman on the earlier /2s, but I don't think there is any room for the transmission to move laterally when it is mounted in place. It must be pulled down squarely to the engine...that is easy to see by looking at the mating crack between the two. But side-to-side...I just don't see it. The clutch disk of course aligns itself to the transmission shaft and if the transmission doesn't move laterally with respect to the engine, I don't see the issue.
    We want to minimize micro-motion on the loaded spline teeth to prevent fretting corrosion. This is a helluva environment having no re-lubrication, high cycle loading (i. e. every engine revolution) and a very radially stiff support for both of the elements.

    On top of that, of course the engine crankshaft is being hammered back and forth thru the main bearing clearance, whenever the pistons are generating power. There isn't much we can do about loose main bearings except being sure the engine and transmission axes are maintained as concentric as possible. This all suggests the spline functionality is optimized with alignments as close as about .001 inch (the new main bearing clearance) - probably unachievable in any used engine. As a result though, a substantial and increasing fraction of the crank main bearing load will be reacted by the transmission input bearing as the engine ages. On top of that, most of the wear on the rear main bearing will be caused by radial misalignment. Piston forces are on the order of a couple of thousand pounds, and it probably takes about 1000 pounds to slide the clutch disk around the flywheel.

    Spline problems have all the elements of a cascading type failure, if the initial alignment accuracy is compromised. What goes around, comes around.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

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