Damaged flywheel and crankshaft - Honda Rebel Forum
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post #1 of 17 Old 10-30-2018, 09:25 AM Thread Starter
 
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Damaged flywheel and crankshaft

Looks like I mangled things up during my oil seal repair. While removing the flywheel, I slightly bent the pin in the crankshaft. Didn't think much of it until the bike starting knocking and shuddering and broke down on me. Opened it up to find that the flywheel had rotated on the crankshaft and the pin had scored the inside of it pretty badly. Assuming I'll have to replace both parts, how difficult will replacing the crankshaft assembly be? Any other thoughts?

BTW, starter chain and sprockets look fine, but I don't know if this could have caused damage on the clutch side or to the camchain or pistons, etc...
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post #2 of 17 Old 10-30-2018, 10:26 AM
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Replacing the crankshaft is pretty major surgery. Hard to say if it is absolutely necessary when looking at the pics, but probably. The dowel slot needs to be good enough to hold the dowel in place, and the hole in the crankshaft to hold the dowel. A machine shop may be able to repair the shaft, but not with it in the bike, and it may be cheaper just to get a new/used one.

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post #3 of 17 Old 10-30-2018, 10:44 AM Thread Starter
 
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Quote:
Originally Posted by flitecontrol View Post
Replacing the crankshaft is pretty major surgery. Hard to say if it is absolutely necessary when looking at the pics. The key way slot needs to be good enough to hold the key in place. Not sure, but it looks like the key is sheared off in that picture of the hub.
The dowel isn't actually what bent. When trying to knock off the flywheel, the hole in the crankshaft that the dowel sits in deformed a tiny bit (or so I thought) which allowed to the dowel to have a little bit of sideways play. In the picture, the dowel is actually wedged in sideways in its now deformed hole in the crankshaft.

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post #4 of 17 Old 10-30-2018, 10:51 AM Thread Starter
 
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I actually found a post of yours @flitecontrol in the "How do I remove the crankshaft?" thread that lays out the major steps. I'm wondering if it's worth the trouble or if I should start shopping for a new engine?

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post #5 of 17 Old 10-30-2018, 11:24 AM Thread Starter
 
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Found someone who did the exact same thing here: https://www.google.com/url?q=https:/...Gq1bQoPKeFjrx4

Unfortunately, they never posted their solution. If I were to smooth out the shaft and the groove on the interior of the flywheel, then remount it and torque it to spec (which I failed to do and probably caused this), could it work? Is it true that it's only the taper that keeps the flywheel from rotating on the shaft and the dowel is only for registration?

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post #6 of 17 Old 10-30-2018, 12:06 PM
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I'm not sure if the taper alone would hold it on, but I can personally attest that it's a bear to get the flywheel off without the right tools. You could try smoothing out the gouged shaft and putting a new dowel in and see if it holds. Wouldn't hurt to add some weld to the dowel hole, then drill it out so the dowel doesn't wobble. Or you might be ok drilling a new dowel hole in a different position; a better mechanic or engineer should be able to answer that.

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post #7 of 17 Old 10-30-2018, 12:15 PM Thread Starter
 
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Yeah, when I was replacing the oil seal I used the single bolt style flywheel puller and it was pretty tough. When I put it back on, I made the dumb mistake of not torqueing it to spec. Hopefully someone else will chime in about the dowel...thanks for your help!

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post #8 of 17 Old 10-30-2018, 02:44 PM
 
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The taper will not hold it. You need the key. A used engine is probably your best bet at this point. A new crank and flytwheel will cost as much as a used engine, and you still have to do a complete rebuild on the engine.
If you ever do another flywheel removal, be sure to use the proper screw type puller and some impact to shock the taper free. This will get it off with no damage. Make sure it gets properly torqued and staked when it goes back together.

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post #9 of 17 Old 10-30-2018, 02:57 PM Thread Starter
 
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Quote:
Originally Posted by Duckster View Post
The taper will not hold it. You need the key. A used engine is probably your best bet at this point. A new crank and flytwheel will cost as much as a used engine, and you still have to do a complete rebuild on the engine.
If you ever do another flywheel removal, be sure to use the proper screw type puller and some impact to shock the taper free. This will get it off with no damage. Make sure it gets properly torqued and staked when it goes back together.
Well, that's bad news...and just when I thought I had it up and running properly. Thanks for your expertise, Duckster.

Just to be sure, by "key" you are referring to the pin/dowel/key that sticks out of the crankshaft to align the flywheel, correct? Someone on a related thread called a different part the "key"...

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post #10 of 17 Old 10-30-2018, 04:16 PM
 
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The pin acts as a key. normally a flywheel key is a crescent shaped steel tab that sits in a rounded slot in the flywheel and a square groove in the flywheel taper. The pin is not nearly as secure IMO, but that's what Honda chose for this.
The taper alone will eventually slip and affect timing of ignition. (sooner rather than later)

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