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Wenmac Rotomatic issues Empty Wenmac Rotomatic issues

Post  miked Fri Aug 09, 2019 2:39 pm

I have found that while trying to revive a stuck engine, the problem might involve the rotomatic starter. If the crankshaft will rotate in both directions, but locks up after a few degrees,first remove the backplate and check the rod integrity. Since you are smarter that I am you will probably have done this already for cleaning. If all looks OK, then the centrifugal clutch in the drive hub is likely stuck or broken. Remove the hub and examine the back side. You will see the inner edges of the cam which lock on the spring hub. Use WD 40 or something similar and gently move the cam around inside the disc. You will be able to see if it's broken. Once free, hopefully the flyweights will be, too. It is then possible to hold the hub against the spring housing and check that it engages clockwise, and spins freely counter clockwise. Putting things together lightly with a prop and letting the spring spin the crank might throw the weights free of the cam. I have not found a way to disassemble the drive disc for cleaning.
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Wenmac Rotomatic issues Empty Re: Wenmac Rotomatic issues

Post  ticomareado Fri Aug 09, 2019 7:02 pm

Yes, it is virtually impossible to disassemble a Rotomatic clutch plate w/o destruction. The main thing is removing the clutch disc assembly w/o crimping to outer black steel shell against the innards. That is easiest to do if top end is completely off the engine by putting a junker nut on crankshaft with a prop hub for filler and gently tapping the crankshaft out the back of crankcase. However removing top end is not always necessary or desirable. (especially with Mark IIs through Mark Vs). In those instances, the stiff flat blade end of a window glazier's putty knife is the way to go if you don't have a suitable miniature gear puller, although the process of gradually prying around the circumference of the clutch is a bit tedious.

Once clutch is off and it is determined that the innards haven't been crimped, the problem usually lies in the accumulated gunk and rust inside the sealed assembly. First, the crankshaft engagement collar from a broken spring should be permanently affixed to a section of wooden dowel. We'll call this our "spinner" tool. Then we start with some hot soakings in a Dawn detergent solution to loosen things up. Rinse and repeat however many times necessary, always using the spinner tool on the clutch while it is held submerged in the solution. It will soon begin to excrete its bilge. Once the detergent solution yields diminishing returns, time for a final rinse with water and then into the acetone bath for the final purgings, again with the spinner tool. When finished, dry out in toaster oven and give it a good dollop of air tool oil.

I suppose the spinner tool could be chucked into a drill for all of this, but beware of electrical sparks setting off acetone vapors.
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