Doesn't this over-ride the shearing "safety" function and potentially put other parts at risk?
well, i guess if you consider them as a backfire safety valve, i would say yes. can't say if any of my failures were caused by backfire, but i can definitely say i experienced failure just engaging the starter.
They won't/can't stop the backfire, but shear to stop potential damage from a backfire, should one occur.
MM - this is just speculation on my part, but here's the way i see it -- it's not Norton OR Alton, it's BOTH. the norton components had a +/- tolerance factor. lets say, the notron assembly went together and stack up ended up the shy side. alton comes along, designs and builds with similar +/- tolerances, and alton's final assembly tolerance stack up also ends up on the shy side. even though both assemblies are within design tolerance, the tolerance deviation of the two assemblies may be compounded to the point where the final norton/alton assembly just ain't quite right. this wouldn't happen across the board, but only in a few cases where both assemblies are at one extreme side of a tolerance limit. my hunch is the core issue lies within the alton spacer or a component of the sprag clutch assembly. a fix may be as simple as adding a washer to the crank nut. it's not an alton fault - in fact, it's nobody's fault. the problem is, two separate companies designing two complex assemblies that should bolt together, that were designed 50 years apart. did alton have access to original norton engineering drawings? my guess is no. alton may have designed it on the fly around an existing commando without the use of original norton design data. today, there a science and a spec to all this, it's called Geometric Dimensioning and Tolerancing, but for it to work, it would have to be incorporated by both.
You mention sprag strength, but my understanding is that the nub of the issue being discussed here is that Alton uses, instead of the self-resetting Belville/ball clutch on the Mk3, a set of plastic shear pins to protect the bike against damage from kick-back. With the Mk3 you hear "click-click-click" then have another go. With the Alton it's time to pull the primary cover off.
correct! problems seem far and few between. from a piece/part and quality standpoint, the alton kit is excellent, there's something just not quite right between my 74 Mk2 and my alton kit. anyone buying an alton starter, i would suggest, at a minimum, adding a serrated bellville lock washer, thread locker, and bumping the torque to 70 ft.lbs. on the crank nut.
Does anyone have any suggestions to help me when I put the new parts back on? I cannot get the Yves fix. Have purchased new sprag clutch assembly, primary chain, starter chain and new stator woodruff key. Pullers would not remove the assembly as it was unbelievably tight on the crankshaft. The last time before this when I removed it, it came off easily.
