The first time I rode my 17 on a really hot (105 degree) day on the interstate at 72-75 mph it balked when attempting to pass (accelerate more) and at some point blew a rear head gasket.

Talking with builders and reading forums leads me to believe that rear cylinder gaskets blowing at their weakest spot (back of cylinder toward the center) is not an uncommon thing with the 17's , mine blew at 10,600 miles.

A question in my mind is whether sumping created the issue with the head gasket due to reduced cooling oil flow, a well known builder thinks the head gaskets blow due to cylinder studs loosening. 6 of the 8 cylinder studs on my bike tightened either a smidge or as much as 1/2 turn when I torqued them to 20 ft lbs, so maybe it was just things coming loose.

If you have a 17 service manual it has an outdated procedure for tightening the cylinder head flange nuts. Technical service bulletin M1509 was issued in 2020 I believe, it instructs you to only use brand new flange nuts as well as "An additional change is the lubrication of the flange nut. Verify that only the bottom of the flange nut receives lubrication. Do not allow lubrication on the cylinder stud or on the internal threads of the flange nut. " . What prompted the change (a rash of problems? , just someone having a better idea, ??) has me curious. If you switch to s and s flange nuts they say you can re-use them and they provide a different tightening procedure.

 

That is my guess, but it would be worth a try for him to call HD and get a reference # from them about the issue and take that to a dealership with his bike and see if they can diagnose it. When I talked to the factory, first off beat me to the punch when I said 17-19 she finished my sentence about the oil pump issue. They know and knew about it at the time, they went through 5 revisions within the first year and half from when they were released in 17, **** I think within the first month they already knew there was an issue hence the revised oil pump within 2 or 3 months. Make sure they don't try to trick him up when talking to them, they did that to me, instead of taking responsibility for there known issue, they played word games with me. I made the mistake of bringing up the other issue about building oil pressure in my primary that they fixed with a recall in 19. In my case both issues are causing issue

 

Good info, and interesting question. Makes you wonder

 

Will do , he called the dealership today , they told him not to ride it , or start it for any reason , until they look at it . They're going to pick it up in a couple of weeks and do what they have to do . I haven't spoken to him yet about what they had to say , but I'll pass along the information . I hoping the best for him , hope he doesn't get stuck with a huge bill and has to go a long time without it , he loves to ride .