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[steveW]

Hi Olly B, lovely looking bike, I listened to the utube clip and it seemed to me that the tapping noise did not vary when the revs were slowing down? Not sure this helps, but I dont think it would be the valve train or tappets responsible for the tinny sound, annoying though. Im sure someone else will be able to help more. Steve

[RoSy]

Worn carb slide, back n forth movement ?

[papasmurf]

Does the noise stop if you pull the clutch in?

[Mark M]

Papasmurf, are you thinking loose primary chain? Olly, maybe you should try the "screwdriver stethoscope". Get a long screwdriver, put the tip against the part of the engine you suspect (say, cylinder head) and press your ear to the handle end. Then rev the engine. You will hear the noise much more clearly and you can move the screwdriver around to get closer to the noise. Try it in several areas, cylinder head, base of barrel next to tappets, primary chain cover etc. This way you can narrow down the location.

REgards, Mark

[Olly B.]

Thank you for the very useful tips. I'll turn over your advice on the weekend. Unfortunately, there is still the work that keeps me from repairing.

[Olly B.]

Thanks Mark, the tip with the "screwdriver stethoscope" was good.
The noise comes from the cylinder head exhaust side. It starts at a temperature of about 130 degrees. The valve springs are not broken. I will now heat the cylinder head in my oven to 150 degrees and see if the valve seat or valve guide loosens. I will inform you, if I know more.
Regards,
Oliver

[papasmurf]

Olly B. from your description I really do suggest checking the tappets with a cold engine as they are supposed to be done, before you start any dismantling. Slack tappets sound like a tin of bolts in a spin drier.

[Wheaters]

This could be the exhaust valve sticking open. When it sticks open and the cam has gone round, the tappet clearance will be huge. As and when the valve does shut, it will go with a "clack".