Another tapping topic-sorry

[Black Sheep]

Could well be detonation. Under acceleration is when it would occur. It would stop as you ease back the throttle. Not something you want long term. Sort the ignition timing and you may well find all is well.

[BSA500]

That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  )

[Greybeard]

That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  )

Sorry, I don't want to be a harbinger of doom. I've always understood that when an engine is under load, worn big ends go quiet and slack pistons rattle. No load, the opposite occurs.

[BigJim]

Thanks GB! The amount of noise i get loaded and not keeps me awake. Am now forced to go out for a ride to check any variation. Hey ho, any excuse will do.
 

[Swarfcut]

 Hello Andy    That sounds just like mine, they are both running perfectly. Man and machine in harmony.

 I always considered the original style of  rocker adjusting screw to be a bit p**s poor. As the valve and rocker operate, the contact area of the adjusting screw becomes smaller, tending to wear a depression in the top of the valve, which give erroneous clearances with the feelers. As the noise is louder from the rockerbox, this is where I would start.  A set of Mushroom headed adjusters may be the answer.
 If you think it is too far advanced, close the points gap a bit, this will retard the ignition as the mag then has to rotate slightly further before the points open. Quick and easy as a test without having to mess with that ATD bolt.

   In the meantime it still runs as is, and whatever is knackered  is screwed anyway so use it til it stops. Then you get the answer.   That's  Zen and the art of......
   

  Keep Spannering

  Swarfy.

[muskrat]

G'day fellas.
When the valve stem tip goes concave i use the # of flats either 4 for the adjuster or 6 for the lock nut. 1 flat of the adjuster is 9.61 thou" and the nut is 6.41 thou"
Cheers

[Greybeard]

G'day fellas.
When the valve stem tip goes concave i use the # of flats either 4 for the adjuster or 6 for the lock nut. 1 flat of the adjuster is 9.61 thou" and the nut is 6.41 thou"
Cheers

At some stage I had a car engine tool that relied on the adjuster thread for clearances. Seems a reasonable idea.

[duTch]

 

...... i use the # of flats either 4 for the adjuster or 6 for the lock nut. 1 flat of the adjuster is 9.61 thou" and the nut is 6.41 thou"......

That was the way my Daytona adjustment was recommended- no way to get a feeler gauge in there anyway

[a101960]

At some stage I had a car engine tool that relied on the adjuster thread for clearances. Seems a reasonable idea.

Yes I remember those tools SPQR. They worked very well.

[Greybeard]

At some stage I had a car engine tool that relied on the adjuster thread for clearances. Seems a reasonable idea.

Yes I remember those tools SPQR. They worked very well.

That's the baby.

[BSA500]

That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  )

Sorry, I don't want to be a harbinger of doom. I've always understood that when an engine is under load, worn big ends go quiet and slack pistons rattle. No load, the opposite occurs.

Well I had the crank ground and replaced the shells in Spring.She had a rebore 2 years ago and hasn't done many miles due to constantly sorting out issue after issue(you know how that feels). So I am skipping past that for now and concentrate on the pinking first. Might try closing down the points gap and then perhaps the valve clearence a couple of thou.

[RDfella]

If you have to do a full strip, might be worth examining the journals with a magnifying glass. In the 70’s and 80’s I was rebuilding around an engine a week. Did my own boring etc, but farmed out the crank grinding as it wasn’t worth owning such an expensive machine. The firm I used (they no longer do cranks) were good and I never had a problem – except once. It was a BMC mini engine, and after building I found it noisy. I wasn’t satisfied so stripped it again, but nothing was obviously wrong. Until I took a magnifying glass to the crank and just noticed the shine was interrupted. It essentially had the shape of a threepenny bit, but hardly visible and certainly not measurable. Took the crank back and the grinder examined his machine – to find the stone had a crack in it. I presume the faint irregularity was cutting the oil film. He lapped the crank and all was well.

[BSA500]

If I get the ATU of the mag in one piece what timing figure is recommended to avoid pinking. Its a 1957 lump running as a A7SS alloy head etc. I might get only one chance to get this set as she may not come off easy again or at all

[PDMiller]

A couple of years ago after many years in my ownership my 1952 AJS 500 single developed a real knock on acceleration (acceleration  he he). The bike has manual advance /retard and by retarding the ignition way past where it should be the knock would disappear. Convinced that the big end was the culprit I stripped the engine and took the crank , piston and barrel to my local engine reconditioner. He said they were all fine and suggested that I stop using supermarket fuel and use branded petrol with a lead replacement additive.  The bike is fine now as long as I use proper petrol. Sadly it means a bit of a drive these days because there seem to be less and less of them but worth the effort to not hear that knock.
Your tap sounds a bit different Andy but maybe something to consider.
Good luck.

[duTch]

 It may be way off the mark, but the other day I had a odd sound too, maybe in sympathy, but after a bit I decided it sounds like head gasket 'squeak'....maybe not, but may investigate sometime...(I've done about 14K miles since rebuild and haven't pulled the rocker cover or anything else- except the G-box; ..... if it ain't broke,..... )

 dunno if that's your sound though