I.T 200 woodruff key

I've sheared 3 keys on this bike. The 1st is a mystery. 2nd and 3rd it turns out that I read the torque spec wrong. :bonk: So, that's most likely the cause. My buddy told me to put valve grinding compound on the shaft and slide the rotor on with no key, and snug the nut and spin, spin, spin it. Remove it and putmore on and repeat. So, I'm doing that and I noticed this small nick. Is that a problem? 

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is the key a really tight fit - which it should be

Yes it is. I fired it up and ran it for a few minutes. Tomorrow I'll take it for a little ride thru the orchards. When it goes, it usually doesn't take long. 

slot on the rotor very worn ?

If you are relying on the key to keep the flywheel located in a running engine, you are doomed to fail.

The key shears because the flywheel spins.

Lapping the flywheel  to the crankshaft is important as is using an impact wrench (carefully).

The key snapping is a symptom and not the cause. Basically the fault is one of two things. Either the nut is not tight enough, or  the split washer is not there/flat. On a 30yr old bike, it’s alarming the bodges you see, so it coul be a cannibalised crank/magneto

My PE had a helicoil within a helicoil, a lighting coil missing, imperial nuts and bolts all over the place. All the good stuff you don’t find out until after you’ve bought

20 hours ago, S.O.A.N.Z said:

slot on the rotor very worn ?

No. 

I didn't take it today as there was nobody home to come get me if......

I did start it and run it up and down the street a bit. So far so good. 

When you put the flywheel on give it a few good taps with a steel hammer to seat it. It's the taper of the shaft that locks the flywheel, the key is just there to locate it. (And act as a failure point when you have another problem, so instead of breaking the crank or another expensive piece you end up with a snapped key).

45 minutes ago, smirmeister said:

When you put the flywheel on give it a few good taps with a steel hammer to seat it. It's the taper of the shaft that locks the flywheel, the key is just there to locate it. (And act as a failure point when you have another problem, so instead of breaking the crank or another expensive piece you end up with a snapped key).

EXACTLY! Just parroting previous post to help drive home the importance of understanding the function of the taper and the key. The taper is what holds and maintains the clocking of the hub when propely seated, key is for alignment during assembly only. 

Surface prep of the taper on both crank and hub, cleanliness of surfaces, proper installation with new or good condition crush/belville or ? washer as factory recommended, and proper torque with clean lubed threads ARE critical! Key is merely for alignment only and designed to shear if something is amiss, sudden engine stoppage, etc. 

Hope it turns out well and many good riding miles ahead.

 

Edited by BRAAPZ
Typos

Also make sure there is no crap like old thread locker on the inside of the flywheel, that got me once. Apparently someone thought that was required, it didn't seem to do any harm but it was just a pain to get it all off and I missed a thin, translucent bit of it. 

Edited by DirtShow

Your buddy has the right idea. The Woodruff key is there more for flywheel positioning than for accepting spinning torque. The taper is an interference fit. That's why a puller is needed to remove a flywheel. If you're familiar with drill presses, think of the taper fit of a Morse taper drill sleeve. Your crankshaft looks worn from the flywheel spinning on it, but you might be able to save it. This looks like a good link to reference. Make sure to use Prussian blue paste, not layout blue. Don't worry about the nick.

http://www.pbase.com/mainecruising/fitting_a_prop

Edited by 76xtdrvr

Very clever way of using valve paste. Save a ton of money having built up and honed at a machine shop:thumbsup:

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