I performed an fork oil change on my bike and the lower triple yoke snapped when I torqued the bolt. I purchased the bike from an elderly man who kept it under a shed. I was just going through it to get road ready when the pinch bolt snapped the alumium. My question is if the technical manual torque spec is wrong (30 ft-lbs) or if the cast alumium becomes brittle after 30 years. Note that the area we live in is coastal SC.

 

What my manual says.

Maybe overtightened in the past?

See any sign of darker area in break.



What does it look like? Hope you can find that part.

 

It was really tight when I loosened it. It may have been overtightened before. The break looks clean but I found a site about airplane frame aluminum weakening with age in salty environment. I ordered a new one from JP cycles but I don't like aftermarket parts because you don't know what quality controls are used if any. Also I don't like just changing parts without understanding the cause of failure. Navy OCD. Thanks for all ideas. It's helpful.

 

I programmed the wire EDM machines at Newport News Shipbuilding. One of the machines was a Navy Veteran. Machinist Mate is the term he used for his career I recall. Think you, him and I think alike.

 

Maybe someone thought the gap had to close that exists in the clamp to fork tube which of course would put tremendous stress on the metal.

 

I would get a used OEM from eBay. You need a press to get the stem out unless you get a used one with the stem still in it.

 

The triple tree brackets are cast, so there is a possibility that air bubbles can form in the finished casting, that especially happens when components are cast from "monkey metal", also known as "pot metal", it is a mixture of what's available in left over low melting point metals which are thrown into the melting pot and cast. The resulting metal has a grainy internal texture which is easily fractured.

I don't think for a moment that H-D would use monkey metal, but I remember the fork axle clamps on Triumph twins and triples were cast from monkey metal and they were frequently cracking. I had to regularly replace the axle clamps on my T140E and T160V due to fractures.

A fractured Triumph front axle clamp.

 

There's no 'monkey metal' in Harley Davidson's aluminum triple trees. That's structural grade aluminum. Now ever material has a limit before cracking. Being a casting, that elastic limit when reached will be unforgiving.

Harley's motto is same as the #1 aircraft carrier and nuclear sub builder is, only good motorcycles, at a profit if we can, at a lost if we must, but only good ships.

Someone overtightenen it, and probably like Dan said tried to close the gap. My model requires anti-seize to that bolt and 35-40. All other 04 Softails 30-35 and no anti-seize

And the lower axle clamp will do the same on a Harley Softail if you don't bottom the front one 15-21 lbs and the rear torques last.

One needs a OEM service manual to SAFELY work on different motorcycles. This kind of stuff can get you worst then dead

Now I am referring to later model Harleys'. Not the bowling ball ones! Interestingly, my friend has a Sporty with the bowling ball logo on the tank. Way over 100k on it. I put the belt and drive pulleys on it long ago.

Still runs like new, other then the 3rd belt and second set of pulleys and maintenance, never missed a lick.

I know, save you the trouble....