After an extended warmup, the oil/petrol mixture would have been even worse as a lubricant - when still cold you'd have had more protection. When it warmed................
I'd put money on it being directly related to the oil/petrol mixture, whether it's a bearing in the clutch or a ring issue or even a cam which stuck slightly I can't tell you.
I just hope with the new oil you don't hear it ever again..............

 

thx pete, I agree.. I hope to never hear it again.. now reply to my damned float height question thread!!!!

 

Dean0 answered it better than I ever could !
But for my 2c worth, replace the needle and set/parts/o-rings whatever on the 4th carb at least............

Happy now ? hehe

 

I'm going to echo Juliet's post.
What have you spent all that money on? What have you done to her in the first place? It's always good to have some history. C'mon..... spill the beans!

This is a very weird symptom and if it isn't complete coincidence that the noise started when you tweaked the pilot screw of No. 4 then it does indeed point towards piston ring screech caused by massive fuel floding, especially as it only appears to happen between a fairly narrow rev band. Was #4 running very rich before you adjusted it?
When you first started it up and the noise appeared did you have it on the side stand? Having the engine out of level can make it harder for the oil pump to get oil to the high spots, which would be everything to do with #4.

It'll be interesting to see what you find in the carbs.

When you take the rocker cover off it is possible to run the engine with it removed. All you need to do is put some kind of shield over the cam chain to stop the oil being thrown all over your clocks, and you. This will give you a real insight into anything untoward happening in the top end.
If you're going to do the valves, check them real carefully but that noise is nothing to do with valves IMO.

My first thought on hearing it was a dry camshaft.

 

Ebinz. Just caught up on the latest posts. It certainly sounds like one bore was being washed clean of oil. Hopefully there's no major damage, just run the motor in again like you would a new one. If it was my baby I'd run low revs and light loads for the first 500km, gradually increasing and varying both (to prevent glazed bores) over the next 1000km at least. It's hard to be restrained but well worth it in the long run..Just my opinion..I hope you've got away with it mate otherwise it's a hone and new rings. fingers crossed .