It’s been about 5 years since i have pulled a flywheel and a clutch from an airhead engine. I do remember the process being slightly ‘dangerous’ in that if you don’t remove the clutch properly, the force of it could cause harm to yourself or your motorcycle. I don’t have the BMW ‘special’ tools at my disposal to do so safely… so i figured i would make my own. Total cost – $10 from my local Ace Hardware store (which happens to have the best spare bolt, nut, screw selection i’ve ever seen).
No need for the BMW Special tools.
Clutch Removal
You will need to purchase three M8 x 1.00 thread (fine thread) bolts about 2 inches long.
i also purchased a small piece of aluminum tubing that fits around the bolt:
M8 x 1.00 bolts and aluminum tubing. Bolts cost $1.50 each(damn pricey metric fine thread bolts)and tube was $2.20
The first step is to remove every other bolt on the clutch disk that secures it to the flywheel:
I cut the aluminum tubing into three sections about 3/4 inch.
Then screwed in the 2 inch long bolts with the tubing on it into those every other holes:
Bolts with spacers on them
The reason for the bolts with the spacers is to safely alleviate the pressure into a ‘second’ stage. When you remove the three remaining ‘factory’ bolts, the disk’s pressure releases itself outward, safely, onto the spacers:
Clutch pressure now lessened and on the bolts with the spacers.
Now it is simply a matter of removing the remaining 3 bolts, evenly, until the clutch disk is released.
If your bike has these spacers, Keep them! Some clutch disks don't.
Clutch bits, friction plate, etc...
Flywheel Removal:
To remove the flywheel, you have to prevent the engine from turning while removing the flywheel bolts that secure it to the crank shaft.
Also, without securing the flywheel, you can also run a risk of knocking the inner thrust washer (around the camshaft) off the pegs within the inside of the engine block. SERIOUS damage could occur within your engine case if that happens.
BMW recommends a ‘special tool’ but it is merely a device that locks the flywheel in place.
I made my own from a piece of steel for $2.00.
12" piece of steel.
After some quick cutting and drilling, I have my very own version of the ‘special tool’.
Use the original flywheel bolts, and finger tighten them as much as you can and you are now free to use a nice breaker bar, a 17mm socket(i think) and crank out those flywheel bolts.
Some suggest using a center punch and making a small score on the crank shaft and another on the flywheel so you can put the flywheel back in the exact same position and your TopDeadCenter mark is still accurate. Using a permanent marker might do the trick for a short term solution.
Piece of steel, cut and drilled out to prevent the flywheel from moving.
That’s it! Now that the flywheel is removed, time to send it off to get lightened!
Another note while the flywheel is out… some people put white paint on the timing marks so you can see them better when timing. Just a tip….
Oh… and remember to THROW AWAY the 5 flywheel bolts. They are torque specific bolts and once they are torqued to spec, the can’t be used again. If so, they may wiggle back out and cause some SERIOUS damage.
For more info on clutches and flywheels, look here:
http://bmwmotorcycletech.info/flywheelremovalwarning.htm
http://bmwmotorcycletech.info/clutch.htm
Measure your clutch parts – http://w6rec.com/duane/bmw/clutch/index.htm
Northwoods airheads sells a $4 crankshaft blocking bolt to prevent the crankshaft from moving forward when removing the clutch / flywheel.
it is located here. http://www.northwoodsairheads.com/Tools.html
Before you start the job, my friend Mike had this to add after reading my initial post.
One of my links refers to the crank blocking.
Here is what he has to say.
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I just saw your blog on clutch and flywheel removal. To add:
Block the crank! some people unscrew the rotor bolt and then bolt up the cover so it pushes on the nose of the crank. I use a piece of angle and bolts and snug to keep from moving. Forward movement of the crank can drop the thrust washers.
The clutch bits should be marked and re-assembled in the same orientation to each other as they came out. BMW put paint marks that should be oriented at 120 degrees of each other when assembled correctly.
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Hey Man thanks for the nice write-up. I am doing the same thing right now and don’t feel like dropping hundreds on tools that I will only need once every 5 years or more. I have also read about the “blocking the crank” warning as relates to losing the thrust washers. My understanding is that the movement that is being guarded against is not rotational but lateral, or in this case transverse? That is forward and backward. I have yet to find a proper diagram that explains this, but the tool I’ve seen is the one on the Cycleworks webpage that is a nylon bolt that is crammed into the front of the crankshaft allen head, and then the front engine cover is threaded on and tightened, but not all the way, so the crank is secure against moving forward. Surely if this is correct, there is no concern about rotational movement because no little wimpy nylon threaded bolt is going to stop rotation of the crank.
Yes, you are correct. you do need to prevent the crank from moving forward and backward. I have never seen it happen, but if it does, you can be in a big mess. In my case, i ended up removing the crank from the engine so i wasn’t too concerned. My engine case is currently completely empty, painted, and almost ready for a complete rebuild.
If you are not planning on tearing the engine down, and need to remove the flywheel, then play it safe and block the crank. You can read more about it here: http://bmwmotorcycletech.info/flywheelremovalwarning.htm
The inner and outer thrust washers control the crank’s lateral play. The inner washer is between the crank and case, not the cam, and is subjected to the most wear. If it’s excessive then it’ll fall off the two pins that hold it in place. It’s wear is measured by setting a dial micrometer against the alt bolt then pushing the flywheel forward. BMW makes two larger sized outer thrust washers to take up the slack. The various shop manuals give the specs to determine which one to use.
I checked out my 73 R75/5’s @ 51k and found it barely worn so reused the original red outer washer. A buddy’s 71 R75/5’s didn’t require the first size over until 179K. Maybe ours lasted longer because we changed oil more frequently and didn’t ride like crazy.