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sounds to me, you have a sheared woodruff key. question, is your primary chain the original OE, or a aftermarket replacement? IF the cause is a failed wookruff key, i have a theory that it stems around the crank nut and the alton spacer. the crank nut has a step flange - that step flange corresponds to a mating step on the crank. IF those mating surfaces make contact BEFORE full clamping torque is achieved on the nut to sprag clutch surface, you'll get a false torque reading on the crank nut. i'm thinking this is all caused by a tolerance stackup issue between the alton spacer and various norton OE parts. the whole alton design relies on the clamping force of the crank nut, and i'm thinking the problem only affects a very small number of bikes. i personally have had two failed woodruff keys. the first failure, i literally had to destroy the alternator rotor during removal. dodged the bullet on the second failure. i then opted to incorporate the famous "yves" fix. since then, no further issues and problem solved. good luck with the repair. keep us posted as you dig into this - post some pics if possible. an easy fix requires adding a serrated belleville spring washer, thread locker, and upping the torque on the crank nut to 70 ft.lbs.

<blockquote data-quote="joe czech" data-source="post: 632954" data-attributes="member: 10039"><p>sounds to me, you have a sheared woodruff key.&nbsp; question, is your primary chain the original OE, or a aftermarket replacement?&nbsp; IF the cause is a failed wookruff key, i have a theory that it stems around the crank nut and the alton spacer.&nbsp; the crank nut has a step flange - that step flange corresponds to a mating step on the crank.&nbsp; IF those mating surfaces make contact BEFORE full clamping torque is achieved on the nut to sprag clutch surface, you&#039;ll get a false torque reading on the crank nut.&nbsp; i&#039;m thinking this is all caused by a tolerance stackup issue between&nbsp; the alton spacer and various norton OE parts.&nbsp; the whole alton design relies on the clamping force of the crank nut, and i&#039;m thinking the problem only affects a very small number of bikes.&nbsp;&nbsp; i personally have had two failed woodruff keys.&nbsp; the first failure, i literally had to destroy the&nbsp; alternator rotor&nbsp; during removal.&nbsp; dodged the bullet on the second failure.&nbsp; i then opted to incorporate the famous &quot;yves&quot; fix.&nbsp; since then, no further issues and problem solved.&nbsp; good luck with the repair.&nbsp; keep us posted as you dig into this - post some pics if possible.&nbsp; an easy fix requires adding a serrated belleville spring washer, thread locker, and upping the torque on the crank nut&nbsp; to 70 ft.lbs.</p></blockquote><p></p>

[QUOTE="joe czech, post: 632954, member: 10039"] sounds to me, you have a sheared woodruff key. question, is your primary chain the original OE, or a aftermarket replacement? IF the cause is a failed wookruff key, i have a theory that it stems around the crank nut and the alton spacer. the crank nut has a step flange - that step flange corresponds to a mating step on the crank. IF those mating surfaces make contact BEFORE full clamping torque is achieved on the nut to sprag clutch surface, you'll get a false torque reading on the crank nut. i'm thinking this is all caused by a tolerance stackup issue between the alton spacer and various norton OE parts. the whole alton design relies on the clamping force of the crank nut, and i'm thinking the problem only affects a very small number of bikes. i personally have had two failed woodruff keys. the first failure, i literally had to destroy the alternator rotor during removal. dodged the bullet on the second failure. i then opted to incorporate the famous "yves" fix. since then, no further issues and problem solved. good luck with the repair. keep us posted as you dig into this - post some pics if possible. an easy fix requires adding a serrated belleville spring washer, thread locker, and upping the torque on the crank nut to 70 ft.lbs. [/QUOTE]

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