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Friday, November 28, 2014

A Royal Enfield mystery: Case of the busted alternator

Everybody loves solving a riddle, although perhaps not when it leaves your Royal Enfield stopped by the side of the road.

Since 2000, the Royal Enfield "guru of the East" B.R. Gurunandan — call him Nandan — has offered advice to the "Bullet-eers" on his Bulletech Yahoo group.

Often his advice comes as a challenge to figure it out for yourself.

His latest riddle started Nov. 5, with a comment from one member on the subject of "Alternator Clearance."

"May I add my two cents?" he wrote. "Please use nyloc nuts or a dab of medium strength thread sealer on the nuts that hold the stator. I lost my entire primary side and screwed up a crankshaft due to the alternator loosening and locking up the crank."

Nandan was incredulous.

"Gross misinformation with grave consequences to unsuspecting readers can't be left uncorrected," he replied, and he posed this challenge:

"Let's see how many SUSPECTING readers, aka real Bulleteers are here. Anyone (except Pete and Tim) who sees what is wrong in his diagnosis/advice please tell him and group."

Another member offered this explanation:

"I'm sure he was just testing the attention of the group; anyone who's repaired anything in general or an Enfield in particular would know THAT wouldn't happen. In his defense, the advice of using 'thread sealer' and/or 'nyloc nuts' is a good one — his suggested consequences are a bit 'far-fetched' however!"

But this didn't give us the answer to Nandan's quiz, and the original member replied that "Just because you ain't seen it doesn't mean it can't happen."

The victim expanded on the mishap:

"I made the mistake of letting a mechanic change the primary side chain. When he fitted the alternator back, he apparently didn't tighten the nuts enough... I felt a slight grating in the primary, didn't think much of it. At this village we stopped for tea and after a few minutes I started the bike, engaged gear and let go of the clutch. There was a crashing noise and the bike stalled. Tried to kick the engine, engine started. It seemed to be in neutral but it was in gear. Gearshift wouldn't budge. Rocked the bike to and fro, got it into neutral. Engine running, gear shifts, but no drive. Opened the primary case. Alternator mangled, chain piled up behind the clutch drive. All three bosses in which the alternator studs screw into ripped from the primary case inner cover. Crankshaft sheared just at the nut. Enough grinding seen on the inner part of the stator to know it had been rubbing for quite a distance. Seemed like somehow it failed to snag for so long."

So something went wrong. But further responses to Nandan were tentative.

"I really do not think your alternator nuts were lose," offered one member. "If the nuts were lose the alternator would have stuck to the magnet."

So Nandan offered a hint:

"How many of you asked this question: If rotor rubbing the stator can shatter the casing, how come nothing breaks on braking?"

The original poster replied: "The nuts fell off due to vibration. There are only two explanations — one is that the crankshaft snapped first and let the magnet slip out, but that seems unlikely. The other is that the stator got snagged somehow."

Nandan still had not accepted an answer by Nov. 12.

"I'm getting some replies, a tiny handful; by direct email because they fear they may be wrong," he reported.

"All were right about being wrong, sad to say."

And in this post he finally began to reveal the answer. Don't hesitate to join the Bulletech group if you must to view the post. You'll be glad you did, next time your Bullet presents you with a mystery.

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