XB12 engines

[Heavy18]

Can someone explain to me, or point me to a succinct explanation, on the differences between the XB12 engines?

I *think* they were all modded Sportster 1200 engines, but I have read several times where people allude to, say, a 2006 XB12 being different from a 2009 XB12.

What year was the change?
What specifically changed?
Performance wise, is one better than the other?

I have read people claim that the 2009 engine was more "refined" and that leads some people to prefere the earlier engines as they are more ... i don't know, raw, rowdy, lumpy ???

I'm looking for data BUT personal opinions also welcomed, naturally!

 

[Barrett]

XB9 is 984cc....all 2003 models are XB9
XB12 is 1203cc
XB12 debuted for 2004 model year
XB9 and XB12 both share same 89MM cylinder bore size
XB9 has 79.4MM stroke
XB12 has 97MM stroke...identical to 1200 Sportster models
2003-2007 engine architecture with a few subtle differences is all the same.
2008 engine complete architecture and oiling-fueling-charging-ignition-EFI systems all completely revamped
2008-2010 engine internals strengthened from all prior years

Watch this

 

[Heavy18]

@Barrett thank you - despite having watched that a few times I somehow missed the central point that they were talking about all the updates for the 2008 engine... (Amazing that I can even tie my shoes some mornings!)

OK, so I am interested in some subjective inputs here: If a guy wants to buy the Buell XB12 he'll keep 'till he dies, would you make it a pre-2008 or 2008+ ??

That video makes a very compelling argument for 2008+, but at the same time I haven't heard stories of pre-2008 engines just blowing up either... (But I don't get out much.) Also, at the Daytona interview, Paul James says "We've NEVER failed an engine here at Daytona." - and that would imply neither pre or post 2008's failed at that event?

 

[Barrett]

Yes Sir my pleasure.

OK, so I am interested in some subjective inputs here: If a guy wants to buy the Buell XB12 he'll keep 'till he dies, would you make it a pre-2008 or 2008+ ??

2008+

 

[34nineteen]

Let dive a little deeper here... the XB motor is more closely related to a Blast than a Sportster.

An XB motor will NOT fit a Sportster, nor will a Sportster motor fit the XB... unless someone did A LOT of customizing. A LOT.

A tube frame Buell... yes, that was a Sportster motor (rigid mount). A rubber mount Sportster motor will not fit a tube frame bike without a lot of customization.

Also, the difference between the XB9 (984cc) and the XB12 (1203cc) is in the stroke. So, to convert a 9 to a 12, you will need to replace the crank.

On a Sportster, the difference between the 883 and the 1200 is the bore. A lot of people have converted their 883's to 1200's (or 1275's) using a big bore kit.

You can put a big bore kit on an XB motor, but you'd only increase an XB9 to about 1050cc or the XB12 to 1250 or 1275. Granted, there are larger kits out there, but they require the engine to be completely disassembled and the case machined to accept the larger cylinders. This is just the "slip in/bolt on" kits that done require all that work.


And yes, Barrett is correct (as always!) and the 08+up is more desirable.


That said, if you want to build a monster motor, most people stick to the early case due to greater availability of cam choices.