The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: BSA500 on 08.10. 2018 13:20

Title: Another tapping topic-sorry
Post by: BSA500 on 08.10. 2018 13:20
Ok to start a list of what has been fixed/done to pre answer some replies  *smiley4*

1.Crank shaft reground and new big end shells
2. small end bearings checked and one replaced
3. reshimmed crank (2 thou)
4. New primary chain
5. valve clearances checked and set (8/10 thou)
6. All mounting bolts tightened

So now to the issue always tapping just like a to wide valve clearence esp at tickover. When accelerating sounds like small knocking but not. Can hear it as the power comes in then not as I go faster(could be masked by wind noise etc). No increase in vibration beyond the norm as in say a worn big end. Not a small end as I had that last year and it was horrible.
 Took the timing side apart and took off the dynamo chain no change in noise. Levered the crank no movement. No movement in idler pinion. Removed front valve cover no increase in noise.
 Ran over the engine with the screwdriver test and when put onto the rocker feed bolt for the exhaust feed the tapping could be heard/felt. So I am leaning towards cam/followers is there anything I missed??
many thanks Andy
Title: Re: Another tapping topic-sorry
Post by: bsa-bill on 08.10. 2018 13:37
just something that can be checked very quickly, slacken the three larger (front) primary case screws, they can (but shouldn't) sometimes reach the crank - not very likely but an easy one to eliminate
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 08.10. 2018 14:24
Worth a try  *smiley4*
Title: Re: Another tapping topic-sorry
Post by: duTch on 08.10. 2018 19:10

 
Quote
  just something that can be checked very quickly, slacken the three larger (front) primary case screws, they can (but shouldn't) sometimes reach the crank - not very likely but an easy one to eliminate 

 One of the two inner case screws can do the same- but not so easy to check
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 08.10. 2018 20:25
Well no change there. Doesn't sound like screws rubbig on the crank a definate tapping. I took a video on my phone I will try to send it to this topic.
Title: Re: Another tapping topic-sorry
Post by: trevinoz on 08.10. 2018 21:49
It's not piston slap, is it?
What clearance do you have in your bores?
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 09.10. 2018 09:38
Sorry didn't include in my list she had a rebore in the last couple of years and everything looked fine in spring when I took it down to do the crank.
She has horrible pinking but I can't  get the atu off due to the extract bolt not extracting,So I can't rule that out yet.
Title: Re: Another tapping topic-sorry
Post by: duTch on 09.10. 2018 10:31

 
Quote
She has horrible pinking but I can't  get the atu off due to the extract bolt not extracting,So I can't rule that out yet.

 Someone else had the same issue not long ago- if you do a search it may shed some lights (not many puns intended if there was any-except the ones I intended-if there was any)
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 09.10. 2018 12:37
Found that thread(I started it :!)
Title: Re: Another tapping topic-sorry
Post by: Greybeard on 09.10. 2018 18:42
If you look back a month or so you will see that I had a horrible knocking that was a badly worn cam follower. I'd been adjusting the tappets and obviously taking out the slack but the follower was through its hardening and was rapidly wearing, opening the clearance.

Here's a link:
https://www.a7a10.net/forum/index.php?topic=13318.60
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 09.10. 2018 19:02
Yes I remember your continuous bad luck like mine I must have had the bottom end down four times in the last two years.
It is something to check if it seems I have to take it down again. I haven't touched the cam etc for years it always 'looked fine. Strange the knocking noise is more obvious with the crash helmet on. With it off(Sorry officer) it sound  horribly rattlerly and with the exhaust covered not too bad???????
Title: Re: Another tapping topic-sorry
Post by: duTch on 09.10. 2018 19:57

 
Quote
Found that thread(I started it :!)

 So is it stuck/broken again ? The thread I had in mind had a successful outcome and I think Beezamacc supplied a new gear
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 09.10. 2018 20:25
I did have it fixed and I thought it was ok until I tried to remove it and it's not coming off again.
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 09.10. 2018 20:28
I post so many problems I lose track🤣🤣
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 11.10. 2018 08:56
Ok plan of action. After 21st Oct( I want to go to the Offham village meet cars and bikes) then I will try to remove the atu and retime the engine to exclude the pinking.
Then if that does not improve things when she is off road for winter I will start a gradual strip down checking everything in minute detail.
Title: Re: Another tapping topic-sorry
Post by: Black Sheep on 11.10. 2018 10:13
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.
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 11.10. 2018 12:55
That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  *smile*)
Title: Re: Another tapping topic-sorry
Post by: Greybeard on 11.10. 2018 13:32
That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  *smile*)
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.
Title: Re: Another tapping topic-sorry
Post by: BigJim on 11.10. 2018 13:37
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.
 *bright idea* *whistle*
Title: Re: Another tapping topic-sorry
Post by: Swarfcut on 11.10. 2018 13:55
 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.
Title: Re: Another tapping topic-sorry
Post by: muskrat on 11.10. 2018 15:39
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
Title: Re: Another tapping topic-sorry
Post by: Greybeard on 11.10. 2018 19:02
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.
Title: Re: Another tapping topic-sorry
Post by: duTch on 11.10. 2018 19:29

 
Quote
...... 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
Title: Re: Another tapping topic-sorry
Post by: a101960 on 12.10. 2018 08:57
Quote
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.(http://)
Title: Re: Another tapping topic-sorry
Post by: Greybeard on 12.10. 2018 09:53
Quote
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.(http://)
That's the baby.
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 12.10. 2018 13:09
That's the hope. The knocking/tapping/pinking whatever is not noticeable when revving out of gear(plenty of other rattles  *smile*)
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.
Title: Re: Another tapping topic-sorry
Post by: RDfella on 12.10. 2018 17:38
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.
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 22.10. 2018 20:32
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
Title: Re: Another tapping topic-sorry
Post by: PDMiller on 23.10. 2018 08:46
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.
Title: Re: Another tapping topic-sorry
Post by: duTch on 23.10. 2018 09:20

 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,..... *eek*)

 dunno if that's your sound though
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 24.10. 2018 13:22
God knows what the sound is. Generally its worse when cold, but not always. Sometimes there is horrible vibration from either side of the engine felt in the footpegs and another day its fine?????. Sometimes the noises and vibration make it sound like its going to explode then they go away. I know the crank shims are fine,the crank has been reground, small ends replaced and rebored 2 years ago. So top end and or timing are places to look. I know there is some clutch wobble but I need to replace the mainshaft bushes so thats one possible source of vibration. She burns some oil but not enough to smoke probably guides?. So yeah I don't know anymore maybe top end off over winter.
Title: Re: Another tapping topic-sorry
Post by: BSA500 on 27.10. 2018 20:09
well got the atu off in one piece so a check and reset to 5/16