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A little bit of luck, the jugs are in good shape. Not a single scratch inside on the cylinder walls. Just shy of 49k miles on the odometer and I can still see some cross hatch. It IS faint so I will probably hone the jugs when the time comes.
Motor spins free now. Can't detect anything bent or loose, including the damaged piston. Bottom still has to come apart for cleaning of any metal particles that came down thru the piston. A couple of the studs came out with the head bolts.
The tan color on the spark plug and also the condition of the heads and valves ( no real buildup of carbon ) looks pretty normal to me for a bike with that many miles. To me it looks like you had the A/F mixture close. I wouldn't call what I see as the motor running lean. As to the cause, something kept the valve open and when the piston contacted it, it broke. As you've mentioned likely due to something with the pushrod/lifter.
The tan color on the spark plug and also the condition of the heads and valves ( no real buildup of carbon ) looks pretty normal to me for a bike with that many miles. To me it looks like you had the A/F mixture close. I wouldn't call what I see as the motor running lean. As to the cause, something kept the valve open and when the piston contacted it, it broke. As you've mentioned likely due to something with the pushrod/lifter.
Oh... I would suspect like someone already said... "Hung a Valve"... Not fitted properly my bet!! Been Really Hot here anyway..sure that didnt help
As I mentioned earlier about blowing thru the push rods like a straw. Very difficult to blow thru the rear intake pushrod so i took it apart the best I could and sure enough there is something in there. Hard to get on camera but there is something in there. With the discoloration around the rear intake valve area and the gaskets being cooked, I'm starting to think that restricted oil flow to the rear intake is the cause.
Also found a couple pieces inside the breather gear. These are aluminum and color matches the inside of the case. Spark plug is there for size comparison.
Holy sh*t!!!
Rear cylinder! When I put the new S&S adjustable push rods in I blew thru 2 of them like blowing thru a straw. I should have tested all 4. the rear intake push rod had almost no passage. Looks like almost no oil flow to the rear intake. Got hot enough to break/seize/crack the intake valve and destroy my top end.
Seen a number of trashed motors from a dropped valve the way that one stuck is a first. Usually they don't have as much stem left on them, heads will pop off where the friction weld was closer to the bell curve, That's why she locked up and didn't rattle around chewing everything else up bad. Combustion chambers usually look like somebody took an air chisel to them.
It just dawned on me that when I rebuilt the 80" shovelhead the cylinders where 3.50? bore so I ordered pistons that where 3.498".
Now I'm wondering why my evo jugs are measuring at 3.498 . . . ?
Because OEM stock bore pistons measure 3.4963 (+) or (-) .00002. Wiseco stock bore forged pistons will measure 3.4955 with the same variance of .00002
The little secret people will not tell you - the proper piston/cylinder clearance is manufactured into the pistons. A cast piston will be larger than a forged because you're supposed to bore and or hone to the precise called-for size and the pistons will have correct clearance.
I know this is gonna ruffle some feathers and never hurts to double check, but that's the way it's supposed to be done and most people are too lazy to measure precisely with calibrated tools.
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