Tappets playing maracas?

[Triton Thrasher]

Others may know better, but I think that pretty much rules out the head gasket.

Richard L.

It does not rule out a blowing gasket.

Combustion pressure is much higher than compression pressure.

That's why the engine runs and powers a bike.

[Butch (cb)]

So that was a pointless test then?

If I was going to pull the rocker box to tighten the head bolts I'd pull the head for a look at this point anyway.

[RichardL]

Others may know better, but I think that pretty much rules out the head gasket.
Richard L.

It does not rule out a blowing gasket.
Combustion pressure is much higher than compression pressure.

TT,

Appreciate that excellent point, but trying to reckon the mechanism in a blowing head gasket that leads to intermittent  "maracas". On the other hand, pinging is something that occurs intermittently. I wonder if that's something to consider as the noise source?

Richard L.

[muskrat]

Good point Richard, it could/might be pinging (detonation). Otto, retard the ignition timing a few degrees or use a higher octane fuel (or a booster for your fuel).
Cheers

[roadrocket]

Yes, I know how pinging sounds in my MG, and I have had the problem on my B 40. If this is pinging however, it is a much metallic sound than the clicking sounds I have experienced before. I will try to adjust the cam ring, a pour some octane booster in.

[Joolstacho]

I once had a similar problem, which sounded a bit like excessive tappet clearances but different. I checked and re-checked them, I was running dural pushrods so at first I suspected something there, but in the end it turned out to be as follows. When I got the bike the camshaft (357) was worn, so I had a local cam-grinding company (Wades, Melbourne, remember them?) to regrind my camshaft, -they had a 357 grind pattern so all seemed ok. But what I hadn't realised was that, although they reground the cams correctly (I checked using a timing wheel), the grinding process had removed a touch too much height off the camshaft, resulting in the tappets not following the cam profiles at the lowest point of the cams, and the tappets were clattering against their 'stop' screws on the base circle positions. More to the point, I think I may also have had Wades regrind the tappets too (wish I could remember exactly what it was, sorry I can't be more precise, but I know it was one or both of these things).
All fixed when Bob Joyner sent me a shiny new 357 camshaft!

[bsa-bill]

If this is pinging however, it is a much metallic sound

Pinging in my experience on my RGF (alloy head) was a very metallic sound, I'd go as far to say that it's a sound that you would not associate with combustion,

[duTch]

 That's good point JoolsT, and something that was discussed a couple of years (or so) ago- I can't remember if I addressed it on my rebuild or not, but always in the back of my mind

 Can you do me a favour and edit/modify this..?...sound like you 'wrecked it'.. makes me think of any Wreckless Eric song

.......excessive tappet clearances but different. I checked and recked them,.....

[Joolstacho]

Har, har Dutch, you are so right and I am suitably admonished!!! Spelling fixed. Sorry. (Though I might have 'recked' a few things in my time this wasn't meant to be one of them).

(The funny thing is I used to work as an Art Director in ad agencies, and used to have a whale of a time going 'round looking over copywriter's shoulders correcting their crap spelling.
Point is that I was a supposedly an illiterate arty bastard, and they were supposed to be the literate good spellers! They actually knew sweet F.A. about the Queen's English!

I was in a major national retail store yesterday, and was amazed to see a large row of very expensive lit signs displaying some tosser's confusion with the plural and the apostrophe.
How do these people get away with it? It's gone all the way from basic design through artwork to lightbox backlit signage without anyone picking it up.

Don't get me started!!!!

[muskrat]

Any more than 60 thou off the cam base circle or followers (or both combined) will give you that Jools.
An old fella once described pinging as sounding like a stick being rattled around in a jam tin. Not far off.
Cheers

[RichardL]

B,b,but, the overzealous cam grinding would not seem to explain intermittent maracas (or, are they really castanets and Roadrocket's bike is haunted by Flamenco poltergeists?)

Richard L.

[muskrat]

The intermittent bit sugests pinging. Under load up a hill or acceleration.
Cheers