Keyway damage on flywheel and timing cam

[David Fallang]

I acquired an FD-12 (1958 Johnson 18 hp) with no visible damage. Getting the flywheel off was a real challenge. I used two different kinds of pullers, whapped the top of the crankshaft a couple times, used penetrating oil, even heat. I rotated the flywheel and tapped it from the bottom upward with a rubber hammer. After two days, it finally “popped”. Now I think I understand why it was so difficult. It appears that sometime in the past the motor struck something and slightly damaged the keyway in both the flywheel and timing cam:

So, I’m asking for input… Is this damage severe enough to attempt some kind of remediation? From what is visible, the key itself appears undamaged.

1. The timing cam shows the key is slightly deviated in a clockwise direction with a little visible damage to the clockwise edge of the slot but I don’t know if this is enough to cause a timing problem. I found a replacement cam online just in case. Any suggestions on how to get the old cam off? Can it be repaired?

2. The flywheel keyway also shows slight damage on the clockwise edge, but at least half of the keyway appears normal. Does the visible damage need to be addressed? If so, how? A tiny weld? Some kind of filler like JB Weld?

3. If I get the cam off, does the key itself need to be replaced? If so, any suggestions on how to get the old one out and a new one it? (Hint: Orthopedic surgeons motto: “If it won’t fit, FORCE it. If it won’t force, get a bigger mallet.”

Ps. I’m missing the “Golden Seahorse” medallion. I know I can get a decal to replace it but that’s so lame. Anyone know where I can get a real one?

[crosbyman]

not pleasant but how does the engine run with these ” imperfections” ?

Joining AOMCI has priviledges 🙂

[dave-bernard]

seems to me the key is the wrong one. get the correct on cleaan things up aand you should be good to go. JMHO.

[frankr]

Very interesting. I’ve seen lots of motors with similar damage to the flywheel and crankshaft keyways, caused by running a loose flywheel. But never have I seen such damage to the cam.

Whatever the cause, in my opinion, the flywheel and cam need to be replaced. And the shaft needs to be cleaned up shiny clean and inspected. The cam and key are no problem, there are lots of them around. I probably have a couple of them lying around myself. Flywheel might be a bit harder to find, but there were a couple of trainloads of those motors made and stuff is out there.

Cam is no problem to remove. Beat it off however you have to. Key is supposed to be tight, but will come out with a little persuasion.

This is important to avoid repeat damage–When you put it back together, make sure the shaft and flywheel tapers are clean and dry and use a torque wrench to tighten the nut to 45-45 foot pounds.

[David Fallang]

Don’t know. I just picked it up last week. I tested the spark and got strong spark on one lead and weaker spark on the other. The leads were very corroded so I’ll change them. Of course, opening of the points is not an instantaneous event – it follows the outline of the cam. The question is whether the timing could be thrown off enough to affect performance. My guess is that it would not, but I’m not sure.

[David Fallang]

I noticed that also. I looked it up and it is supposed to be a “Woodruff key” – half moon shaped. I agree that the key in the photo does not look correct. Interestingly, the keyway extends all the way to and through the end of the crankshaft which I suspect it is not supposed to do based on the shape of a Woodruff key. Did someone extend this slot and then put in an incorrect key??? If that is the case, will the “correct” key actually not work? My guess is that you are correct – clean it up, put in a new key (replacement timing cam has already been ordered) and it will work fine. Time will tell. frankr’s comment above notwithstanding, I thing the flywheel will be OK. Half the keyway appears intact. Besides, I couldn’t quickly find a replacement flywheel, although I didn’t search for long.

[dave-bernard]

Lap the fly wheel before installing.

[Mumbles]

I’d definitely replace that flywheel as it is starting to crack next to the keyway. Flywheels from 18 and 20 horse motors thru the early seventies will fit although they are a different design. The same 316583 cam and 120395 key were also used on later 5.5, 6, 10, 18, and 20 horse motors so there are plenty of them out there.

Here’s a ’58 FD which I used a later flywheel on as the original one was NFG to.

[frankr]

David Fallang wrote:

Don’t know. I just picked it up last week. I tested the spark and got strong spark on one lead and weaker spark on the other. The leads were very corroded so I’ll change them. Of course, opening of the points is not an instantaneous event – it follows the outline of the cam. The question is whether the timing could be thrown off enough to affect performance. My guess is that it would not, but I’m not sure.

Actually, it is an instantaneous event—within reason, of course. The points are supposed to just barely break contact at a certain time as the flywheel magnets pass by the coil laminated core. Yeah, thanks to OMC’s reliability, it will run to some degree, even if it is out of spec—but how far out of spec and how well it runs is the question.

[dave-bernard]

just noticed the key is in backwards flat should be out ib the cam and flywheel and curved in the crank !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

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