Woodruff Key Sheared

[skippy1234]

just put engine in bike techno 99 after fitting new mains bike started first go sounded sweet then came to start it half hour later and the kick start nearly broke my ankle found the woodruff key sheared the fly wheel was still firm on the crank as i had to use a puller to get it off not too tight though where to get a new one from and was it caused by not tightening fly wheel sufficient or what else have i done wrong ie timing or anything i fitted stator as it was b4 regards mick also best way to bleed the clutch wich i had to disconect to remove engine cheers

Edited April 22, 2010 by skippy1234

[mikepalczak]

This is so bizarre I felt compelled to join the forum after reading this post. Today, I was working on my 86' Beta TR33 trying to figure out why it had no spark. I popped the cover and voila, the exact same problem!!!! The key sheared off and the nut had backed out a bit.

What I did was I used a valve shim that matched the thickness of the original key, then I cut off the side of that shim approximately the same size as the original key (I used a die grinder for that). Then it was just a bit of grinding to get the size and radius exactly right (I still had the original pieces that I could use as a reference). I put the flywheel back on, put a dab on locktight on the nut and she fired right back up!

On a side note, does anyone out there have access to a rear fender for an 86' Beta TR 33??

[copemech]

These keyways are normally very standard metric sizes and available cheap. Not sure your size, but mine would be considered a standard 3x10 on a Sherco which may be similar as they have used similar ignitions such as the Ducati.

Take your measures and call the auto parts store even. Or just call your Beta rep.

[technowaldo]

always put a bit of valve grinding paste on the taper of the crank then offer up the flywheel and grind the two surfaces together until they mate perfectly then fit the woodruf key and torque it up . it is not the woodruf key thats supposed to hold it in the right place thats the job of the taper the key is only there to make sure it is correctly alligned

[eiger]

Had exactly the same problem with my lads Beta Rev 3 and after replacing the key it sheared again but that was down to me not tightening it up enough as if you look back through other threads the torque setting for the flywheel nut on the Rev 3 is around 103 ft/lbs. And since then its been fine as it was for 18 months prior to shearing.

Check what the torque settings should be but it seems if they are set as per manufacturers instructions it should solve your problem.

[feetupfun]

For the person who made a new key from a valve shim - I suspect that valve shims might be either a fancy grade of steel, or surface coated for hardness, or both.

Woodruff keys are usually made from relatively easily sheared material (something like 250MPa mild steel), so that if the taper slips, the shearing of the key does not damage the crankshaft or flywheel in the process.

[copemech]

For the person who made a new key from a valve shim - I suspect that valve shims might be either a fancy grade of steel, or surface coated for hardness, or both.

Woodruff keys are usually made from relatively easily sheared material (something like 250MPa mild steel), so that if the taper slips, the shearing of the key does not damage the crankshaft or flywheel in the process.

HeHe! this is true!

[jse]

HeHe! this is true!

Yipes!

Yea, Copey and Feetupfun are right. I just caught this thread and when I saw the cut valve shim for a key I figured I'd better chime in.

I would guess that most riders don't know that the Woodruff key is only for alignment during assembly and does not hold the flywheel

in alignment. The special tapers of the flywheel hub and the crank snout (a "Morse Taper") is what makes them "stick together" (also

called an interference fit). You could make a key out of hard plastic and it would still do it's job, probably better, as it would not scar

the taper surface if the hub spun on the snout.

I'd advise that the shim key be removed and you could file one down from a small piece of mild steel strap, which would be pretty close

to the OEM one (I've had to do this more than once). If the flywheel comes loose, the shim key will possibly cause some severe damage

to the taper surfaces and possibly other components.

Jon

[dan williams]

Make one of these to hold the flywheel for tightening. It's cheap and it works. Just be careful the bolts don't go too deep or you'll destroy your stator coils and the poor buggers are delicate enough as it is.

Edited April 18, 2014 by dan williams

[griff666]

Same here think the woodruff key is dead on mine and its now started popping bogging and even running backwards

[0007]

always put a bit of valve grinding paste on the taper of the crank then offer up the flywheel and grind the two surfaces together until they mate perfectly then fit the woodruf key and torque it up . it is not the woodruf key thats supposed to hold it in the right place thats the job of the taper the key is only there to make sure it is correctly alligned

Bingo, Ditto on the lapping and Ditto on the key being only for indexing