Keeps destroying woodruff key, why?
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Joined: 21 Nov 2017
Posts: 45

Tue Jun 30, 2020 9:16 am quote
Hi folks, I have a vbb motor with pinassco head kit. This project has been a nightmare to say the least, the last two things that I've had to replace just to appease my curiosity was stator plate and the flywheel. I could not remove the old flywheel so I had to cut it off from the crank and in doing so I took a little meat from the crankshaft, so I dunno if this has something to do with it. Upon modifying my own Woodruff key from the local hardware store, they keep shearing in half. Is the material of the Woodruff key the problem or is the size that I'm making allowing there to be too much play causing it to shear? Please any help! Thanks everyone


Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2132
Location: London UK
Tue Jun 30, 2020 9:30 am quote
the key just holds position. It's the taper that holds it on. And that taper is finished. New crank is probably the only option.
Kymco Downtown 300i
Joined: 12 Jan 2012
Posts: 51
Location: Hillville, TN
Tue Jun 30, 2020 9:32 am quote
That taper looks pretty rough. The taper provides most of the holding torque and retaining resistance (to sliding off). The woodruf mostly indexes the relative position between the flywheel and the crankshaft. Boogered tapers will lead to constant failures of the key and keyway.
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2557
Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Jun 30, 2020 10:09 am quote
Yup. That taper is DONE.

And if your VBB is anything like mine, the port timings are going to be painfully low with the Pinasco kit if you don't fit a spacer, but then you have squish issues, so it's kind've lose-lose
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5299
Location: So Cal
Tue Jun 30, 2020 10:15 am quote
That crank is toast.
The woodruff key doesn’t hold the flywheel on. The flywheel is held in place by the taper of the crank. The woodruff only locates the flywheel for timing purposes. Grinding off taper has compromised the fit. Sorry, but new crank time.
Molto Verboso
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 1394
Location: california
Tue Jun 30, 2020 10:24 am quote
One thing you might add to your tool kit if you don't own already, a fly wheel puller. It makes the on and off fairly easy and will save a lot of frustration - and dremeling - on the new crank.
Propper key is likely offered with your new crank.

Just out of curiosity - can you fire a picture of the slot side of your crank with the slot in nice focus?
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