Author Topic: timing side rattle  (Read 610 times)

Offline mugwump

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timing side rattle
« on: 12.03. 2021 15:54 »
Hi all, a quick bit of advise needed please. There is a rattle from the timing chest which has started to develope into a light tapping also. I have eliminated the dynamo chain and the timed breather play. There is a little play in the idler bushing but I'm convinced not enough play to cause the noise, I have eliminated the end float to nil. I am concerned that the only thing left is the oil pump. Are these pumps known to get noisy. I believe it is the original ( 1958 ). I daren't try running the engine without the pump even for a few seconds for elimination purposes. I suppose an exchange pump would be the safest way to go. I do have some new idler bushes but as they will require line reaming ( engine strip again! ) I would appreciate any suggestions on how best to proceed. By the way, new main crank bush replace on re-build approx 3000 miles ago.
thanks in anticipation   

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Online BigJim

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Re: timing side rattle
« Reply #1 on: 12.03. 2021 17:14 »
Hi Mugwump and sorry to hear of your tapping. At least the engine is running well enough to idle and reveal this noise. Having a good open minded listen with some sort of stephascope/screwdriver from top to bottom may help to locate the source. I'm sure someone will be along with something more sensible to say soon. My bike is very noisy everywhere and won't idle so i am protected from new worries.
Jamie,  Supporter of Distinguished Gentleman's Ride

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Re: timing side rattle
« Reply #2 on: 12.03. 2021 17:42 »
Noises tend to travel around inside an engine, especially alloy ones. Wouldn't be the first time someone thought their car / truck engine had a water pump noise only to find the problem was at the flywheel end. Which merely adds to the frustration.
In your case, listening with a stick is good advice. Have you checked the tappets? Could be a cam follower noise. I'd be very surprised if the oil pump was to blame. Remember, if oil is returning to tank, then the pump is both delivering and scavenging.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online muskrat

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Re: timing side rattle
« Reply #3 on: 12.03. 2021 19:04 »
G'day mugwump.
if the idler bush is worn the noise could be gear backlash. When turning the motor over by hand you will hear a "click clack". This is the timing gears backlash caused by the valve train resisting the pressure of the valve springs. Most if not all A7/10's will do this. A worn bush ill exasperate this.
Warning Do NOT turn the motor over without the idler pinion in place or the timing marks aligned, bent valves will be the result.
Cheers
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Offline Swarfcut

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Re: timing side rattle
« Reply #4 on: 13.03. 2021 09:19 »
 MG  If you have an auto-advance magneto drive, these are another source of clicky -clack as the backlash in the timing gears gives an element of stop/go rotation rather than a constant drive at tickover speeds. Made worse by the usual wear within the unit. Once under way everything is under load and such noise disappears. Listening with the stick will be a little unnerving to start with, but you will soon the subtle noises from here and there. Maggy bearings come as a shock. How do they sound like that and it runs so well?

  Dynamo drive/idler gear endfloat is eliminated by the cork washer under the drive sprocket, so I assume this is in place. Oilpump runs in oil and is as RD suggests, an unlikely source.

  Tappets, cam followers, small end wear and piston problems are more the source of  light tapping/knocking. Crank related problems have a heavier note.

  The other philosophy is to check the engine basics and primary and dynamo chains, drain the oil looking for metallic debris and if all is in order continue to ride with an ear to the noise. It may simply be "general wear" and if it gets worse, at least the source will become more apparent. There is nothing more frustrating than ripping it apart to find nothing that points to the problem.

 Like musky says, they all make some noise from the timing gears, there's a lot going on in there.  I always feel reassured by the subtle sounds as the various parts go about their business. Like you, I've spent time and money in fruitless quests for perfection.

 Swarfy.


Offline mugwump

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Re: timing side rattle
« Reply #5 on: 13.03. 2021 14:56 »
Thanks for a the replies. After the initial re-build I was surprised at how quiet the engine was, and for a good few  miles too. The problem first became apparent after the throttle stuck open at approx 60mph and continued in neutral till I was able to stop. Warped carb body was the cause. New carb now fitted but persists in running too rich. Still, when I get to the bottom of the rattle I'll report back.
thanks again

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Offline A10Boy

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Re: timing side rattle
« Reply #6 on: 13.03. 2021 20:23 »
Mugwump

I was wondering if the tapping is any different with temperature? Is it the same hot or cold?
Regards

Andy

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Online Greybeard

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Re: timing side rattle
« Reply #7 on: 14.03. 2021 09:57 »
My engine developed a rattle not long after a rebuild. To cut a rather long story short:  The cam followers had rapidly worn out. The cause was down to the valve springs bottoming. I'm still not quite sure how that came about; may be just down to mismatched modern parts. To cure the problem I reduced the thickness of the collars that go under the valve springs.

Offline mugwump

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Re: timing side rattle
« Reply #8 on: 14.03. 2021 12:35 »
I renewed the cam shaft and followers on the re-build and have checked them since and still ok. The noise is more pronounced when hot. I'm tempted to renew just the outer idler bush and try a BRIEF run just to see if that makes any difference,, if so It'll be a compete strip and line ream job. I know engine noise sources can be elusive but I'm pretty sure its to do within  the timing case area. I did renew the a/r unit as the old one was the sloppiest I've ever seen. The new one is like new, but the extractor bolt is knackered. Instead of trying the awful job of renewing the bolt I've simply drilled and tapped the bolt for a 3/16th " extractor bolt, seemed the simplest remedy. Just had another thought as I type.
I had the head skimmed which was bodged and left a terrible finnish, so had it re-done. It might be worth checking to see if the rocker geometry has been affected, ie valve spring binding and associated problems that might cause.

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

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Re: timing side rattle
« Reply #9 on: 14.03. 2021 12:51 »
Trying to wrap my head around the throttle sticking open 'then continuing in neutral'. Did the engine over rev? Did it perhaps partially seize, meaning a piston is marked? Damaged pistons can produce a rattle like a softly-sounding big end.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline mugwump

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Re: timing side rattle
« Reply #10 on: 14.03. 2021 14:07 »
I was stupidly keeping up with a mate on a quicker bike doing an overtake. After the overtake the bike wouldn't slow down I realised what had happened and changed down and braked but the engine continued at high revs pulled clutch in and killed the engine. Although it only over reved for a short while the noise became quite apparent after that.
The carb body was warped and when hot the side would stick at pus 3/4 opening. I assumed that if any damage had been done it would be to the valve train but it all seemed ok.

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Offline Swarfcut

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Re: timing side rattle
« Reply #11 on: 14.03. 2021 19:30 »
    Jeez, It's like the Bermuda Triangle. Loaded Container Ship Leaves Galveston bound for Portland, Maine and disappears. Wow. Mystery. Then they tell us it was a new crew, captain drunk, ship overloaded and heading into a Hurricane, all never mentioned in the original news item. No Mystery, simple explanation.

      Just a few little itty bitty facts missing from the original post.......Throttle stuck open, pulled the clutch, killed the engine. There's the answer, wide throttle, no load, hence major mechanical abuse.  It ain't gonna be cheap.  Get the spanners, arrange finance. Wire up another simple on/off  switch that doubles as a magneto cut out. That way you have a primitive anti-theft device and don't need three hands to bring a runaway to a halt.


Offline mugwump

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Re: timing side rattle
« Reply #12 on: 14.03. 2021 23:12 »
Swarfy, there was no mystery intended. I am aware of the possible cause and possibly should have mentioned it, I simply asked for some advice on possible problem areas of the engine that most contributors to this forum would be familiar with. 

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Online berger

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Re: timing side rattle
« Reply #13 on: 14.03. 2021 23:57 »
I love this forum , especially after I've wound every one up on fb, haha
  QUOTE  " possible problem areas of the engine "  I think most of it now I know it's been let loose at full throttle with no load, sorry for this but I can't stop laughing *lol* *lol*

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Re: timing side rattle
« Reply #14 on: 15.03. 2021 08:42 »
Didn't know you had a Francis Barnet berger!
Bill