If it were better than a Twin Cam, I would have one.

 

All M8 crankshafts that come from the factory in new motorcycles are cast, press fit cranks; just like Twin Cams.

From 1999 to 2002 Twin Cam crankshafts were hot forged as opposed to cast. In 2003 and 2004 they were cold forged; after 2004 they are all cast steel cranks. All Harley big twin cranks are press fit since 1999 with the caveat that the Softail line didn't get the Twin Cam until the 2000 model year (the Twin Cam B). In 1999 the Softails had the Evo engine.

In summary, in 2003 Harley was looking for methods to make production faster and cheaper, that started with the loss of the Timken left side crank bearing, a change to the forging process and ended up with cast steel cranks that forced them to increase the service limit for TIR from .003" to .012".

 

The M8 crank is better than the TCs in a few ways but the number one thing to note is the crazy amount of HP people are now making with the new engine and the lack of discussion of twisted cranks. That in itself should tell you something.
Many people are finding them to be at or near .003 in runout as well - which is much better than we've seen in the past.

The M8 has had some growing pains sure, but the crank anyway seems pretty good in comparison.

 

As an engineer I reckon the change in service limit is entirely down to reducing assembly time and cost, nothing to do with what the crank is made of. To run a set of mating cam-drive gears requires minimal run-out in the crank-shaft and skilled people to achieve that, which is expensive on labour costs and the time required to do that task. Using a cam-chain enables the crank run-out to be relaxed and the task of crankshaft assembly can be reduced to an unskilled job, probably using nothing more complicated than a simple assembly jig.

 

Starts at 1:01

 

Well it might be, if that video wasn't blocked over here!

 

That's what we should do to all you Red coats.

 

Careful what you wish for! The Harleys and Davidsons were all British old chap! In fact the Harleys still live here.....

 

Poppycock! [Nearly] everyone here started out elsewhere first but by Jove they wanted to be American since their families moved here.
The "Harley" and "the Davidsons" we know today were Milwaukee/American born Old Bean... They didn't move here.

Pip pip!