Maybe. Maybe not. The ugly sound was immediate.

Heads off 

If this bike is loved, now is an opportunity to make it perfect. (And for us to enjoy the story and photos of the repair)

Quote from: stopintime on Today at 11:27:13 AMOoops - not so good - sorry for you and the bike.

You will need more luck than usual for the piston not to be damaged. If/when the piston hit that plug it could very easily end up hurting parts behind/under it ( = seized engine? )

New plugs; which plugs are they? (maybe too long?)

I'd agree that maybe plugs too long, but he said it started and ran...then got noisy and stopped. If the plugs were too long it would have locked up on cranking...no?

Ugh.

Was supposed to have my water heater serviced this morning.  Part of a package for HVAC components.  Took the technician 15 minutes to find a street parking space (somehow he drove past a few of them...).  Can't figure out callbox to gain entry to building.  Starts the "service".  Claims W/H is "clearly plugged full of sediment". Claims service can't continue as such. I didn't like his attitude, so I sent him on his way.

Checked the University of Youtube. What do you know...I was able to very easily get the unit to drain.           

Ooops - not so good - sorry for you and the bike.

You will need more luck than usual for the piston not to be damaged. If/when the piston hit that plug it could very easily end up hurting parts behind/under it ( = seized engine? )

New plugs; which plugs are they? (maybe too long?)

One thing is certain. There's something in that cylinder that doesn't belong.

It's really difficult to know. I think people are waiting for more info...like images.

Flounder, thank you. I'm going to pull the cylinder head and hope for minimal damage. I'll upload more videos once I have it off.

In the meantime, does anyone else have a different perspective or anything to add? I'd appreciate any extra insight to ensure I have a complete diagnosis before I dive in.

I believe you're going to see a broken valve, with some possible damage to the top of the piston and combustion chamber in the head. It's also possible there's some scoring on the cylinder wall. Let's hope that the damage is minor and you don't have to dig deeper.

I had a similar circumstance several years ago, although mine didn't lock up as the valves just bent on a race motor from an over rev.

Get the head off, take some images, and the guys here will be able to give you some choices regarding the best course of action.

What should I see when the Cylinder head comes off? What else do you suggest doing to finalize a full diagnosis of the problem?

Flounder, thank you for your help. By the way!

Your diagnosis of something hitting the plug is spot on. The cylinder head will need to come off.

Before that, pull the belt covers. I think one broke, a valve hit the piston, then broke, stopping any further rotation.

You can do a bunch of messing around, but the basic fact is that head has to come off.