On the 4101st km...

[brenton.roy]

Had a call from my mate Simon to say that the VH had holed a piston.
If you've ever wondered what might happen if it pings for too long...
The amazing thing is that the bike did over 4000 km, often under big loads for good distances. Within 10 km from arriving home, it did this - apparently on a warm day with a strong head wind.
I was aware of the possibility of damage from pinging and was careful about jetting. I think I have posted a photo of a tan spark plug, and did go one size larger on the main before leaving.
A guess on the cause is high compression (9:1) combined with low octane petrol. For the bulk of the trip, it was filled with 95 or 98.
I will now aim for the richest setting I can get it to run well at and see how it goes.
There doesn't look to be other damage, but there is some cleaning to do.

[nevhunter]

Holey piston!. She looks a bit sad around the ring lands. Nev

[adrie.degraaff]

I think you need a colder plug.

[brenton.roy]

Thanks Adrie - yes, I'll try that.
The compression rings are glued in and there is a neat blob of aluminium welded into the small end oil hole.
The head looks like it has been metal sprayed and the exhaust valve has blobs of ally under it.
I'm glad there wasn't a lot of damage, but you can see it was very hot.