How far did it overshoot and what was the configuration.. EFI or Carbed. CR, fuel type.

 

it was my 98 Fatboy..
​​​​​​220 rpm over as logged on my WegoIII, Dynatek 2ki set to 6500.. 213 ccp, S&S G, PUMP GAS 93, First gear hard take off did nothing but spin. It happened to me twice. The first time it whipped out the valves.. The pistons survived. The second time a was lucky, did not bend any valves, only collapsed a couple of lifters that did pump back up in a couple minutes.... I now keep the rev limiter set to 6000 rpm. A couple years ago I had a thread running about trying to find better lifters because it was just happening too often never did find any and just decided Harley's are not good for 6500 Plus... Unless you have a lot of money...

 

IF 220 rpm over has the valves kissing the pistons it's not lifters it's a loss of valve train control. Your springs ain't up to the task.

 

While it's physically impossible for a crank to continue to accelerate after power is cut, one has to wonder how the ignition determines when and how to shut down spark. Some might do by what is called a soft shutdown, say retard the timing, They likely do this instead of cutting the ignition as it keeps the motor from backfiring out the exhaust do to the carb still feeding gas.

I'll agree with Larry tho.. You either don't have enough clearance or enough spring..

One thing that was interesting about my 116 build was that even tho the piston to head clearance was both at 0.030, the rear cylinder head had evidence of the piston squishing carbon build up into the head. It didn't dawn on be until the motor blew up that it's possible the rear rod was flexing / stretching to cause the issue.

 

The springs were new BeeHive. I was told, if I remember correctly, spring pressures were 180 on the seat and 360 at .600".. I was also told the P-V clearance was .060".. I never clayed my setup.. I trusted the shop that did the work... I do know that no manufacturer will give positive proof that their lifters will hold up after 6200 rpm...

 

Were you able to see where the valve contacted the piston?

 

I'm not disagreeing with Larry either, definitely one or the other.. I also kept the squish at .030"..

 

I think this is what I found, I'm trying to remember.. I believe I did find a clean spot on both exhaust valve pockets in the pistons, no carbon when there should have been.. it looked like it was nicked.. I don't believe the pockets were opened enough.. So I open them both up a little..

 

So it probably wasn't a valve spring.. You should have clayed it..

 

Without a doubt I should've when trying to build it as much as I did.. but like I said I trusted the shop that did the machining.. As it is I'm very happy with it.. I had to have the crank balanced and went with a different cam.. More like and old school build with long duration.. Haven't had an issue since I got it back... But I really don't take it over 6000 rpm and the cam has .030" less lift.. Insurance..