Keyway damage on flywheel and timing cam

[David Fallang]

OK, I just made it back out to the tank ranch where all this stuff is located and I have to retract a few statements. The photo is a bit deceiving – it fooled me anyway-. I guess it’s the angle I took it from. Upon further inspection in person, the key does look like a Woodruff key and the flat side is facing outward like it’s supposed to. I think the deception was because the photo was end-on. Just at the top of the timing cam the crankshaft begins to taper and from the end view the taper cannot be appreciated. Therefore, it looked (to me) like the key slot was extending to the end of the shaft but that was not the case at all. Some of the slot was more visible than I expected because the tapering crankshaft exposes it. Sorry. The sideview makes it easier to see.

I also measured the length of the key above the timing cam at about 0.53 inches. The length of the keyway in the flywheel measured to about 01.92 inches, so most of the flywheel keyway is not engaged by the key. In fact, the length of the keyway that is visibly damaged corresponds pretty well to the 0.53 inches that is actually engaged by the key. That destroys my hope that the normal appearing keyway in the flywheel would somehow result in normal positioning and function of the flywheel on the crankshaft. Maybe time to look for another flywheel as Mumbles suggested.

[David Fallang]

Mumbles, that looks fantastic! Something for me to aspire to. It looks like you used decals for the “Golden Seahorse” and I’m guessing for the front plate as well. Where did you get the rubber gaskets for the cowling?

[dave-bernard]

Make sure you LAP the new flywheel. And proper torque.
that is what holds the flywheel on not the key. the key is only for alignment.

[labrador-guy]

Dave it looks to me like your flywheel is cracked at the key slot. When you reassemble the torque value will open that crack up some and everything will be out of wack! The previous owner probably tried to over tighten after he found the key way was whopped out. Find a different flywheel, that old motor deserves to run properly. I have one just like it and it is one of my favorites

dale.

• This reply was modified 3 years, 5 months ago by labrador-guy.

[JOHN HOLBIK]

Most people do not believe it is true that the key is for alignment not to hold the flywheel on.I have several chain saws that I advanced the timing on and they now are keyless but if your flywheel is cracked put on a new one.

[Mumbles]

David Fallang wrote:

Mumbles, that looks fantastic! Something for me to aspire to. It looks like you used decals for the “Golden Seahorse” and I’m guessing for the front plate as well. Where did you get the rubber gaskets for the cowling?

The cowl gasket is original but Peter at nymarine has them and everything else needed including the correct decals for the FD-12.

http://nymarine.ca/

http://nymarine.ca/58JO18WEBPIC.gif

http://nymarine.ca/cowlgaskets.htm

[fleetwin]

Yes. you need another flywheel, cam, and key….Shearing the key even that small amount is enough to lose spark altogether. Like everyone has said, you remove the mag plate, retainers etc, then lap the new flywheel to the crank using mild lapping compound with the crankshaft key removed. Please be sure to tape up/seal off the crank/seal area below before lapping. Like John says, the key is only for initial alignment, it really doesn’t hold the flwheel in place, proper crank/flywheel taper fit does that job….
Don’t know what caused the cam to shear also, that is peculiar. This problem is probably due to improper flwyheel fit, under or over torquing the flywheel nut.

[Author]

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