Hey! All the Techs out there...

Working on a 2007 1200 Sportster...Head gaskets have blown on me twice - Cylinder/Heads are not warped. Using factory head gaskets. Gaskets are blowing on left side "small bolt" side. Im begining to think the Cylinder studs & head bolts are weakening on me. When installed i can slighty see a gap which i know is no go from the begining - installing the heads correctly is being accomplished same with removing them.

Just wanted to get some more insight on the possibilites of having stretched studs? Its looking to be my last option. Any tech help would be much appreciated. Thanks

 

Do you have the manual, and following per instructions?

 

Are you using new head bolts, or still reusing the original ones?

 

How did you check the heads for warpage?

 

Have service manual - flat edge for warpage - Head did not exceed .006" and cylinder did not exceed -008". I am re-using head bolts, should i look to replace them?

 

Yes! Not good to reuse head bolts.

 

Acronym. These new '04+ XL's don't have "spigots" anymore, the head and cylinder surfaces are flat. Used to be it was a "spigoted" interface, looks like a sleeve, sticking up a little bit. This kept the burning gasses from directly contacting the head gasket. Sometimes this is a problem, sometimes it's not.

The gasket makers are onto this, you might try new gaskets. Harley themselves might even make a set because this "no more spigot" decision must be haunting them. It was a bad decision, made for ease of machining, they were probably hoping that it wouldn't make that much difference.....but it is proving to be a big difference.

The gap you see upon installation may be normal, having to do with the coefficient of thermal distension differences between all the various materials, gasket, steel, aluminum. I don't know. But I'd just bet that the factory engineers definitely addressed this issue, because like it or not, physics is physics. The solution may well have been to use a "loose gasket" cold, which seals perfectly once everything is all expanded by heat.

Look for signs of "combustion impingement" on your blown gaskets. Better yet, sent 'em off to NRHS, ZIPPERS, BRANCH & O'KEEFE, et.al., bet they can tell you why. It may well be "impingement", same place, both cylinders....the odd's that head-bolt stretching is the culprit is unlikely because it'd require the EXACT same flaws, on BOTH cylinders. What if the actual combustion is "weighted" towards the left, by design or accident? Lot of hot gasses, hitting the gasket, in any case. Bring back the spigots, I say. Nobody ever had these complaints before, oh, a lot of other complaints, but head-gasket blow outs were never one of 'em.

 

Did you also check the deck on the cylinders for true?
Head bolts should not be reused. They stretch in order to achieve their proper bite, and once torqued will not properly retorque with accurate readings, plus will be weaker.