Author Topic: Identifying a rattle  (Read 5070 times)

Offline K1100

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Identifying a rattle
« on: 14.01. 2013 21:04 »
Hi everyone and happy New Year. I am about to remove the head on my '54 A10 to replace the gasket to stop my last oil leak, but at the same time I want to deal with a top end rattle that I thought was an over-big valve clearance, but isn't.

This noise according to my listening stick is definitely at the top, on the left side only, and increases intensity when I rev, then fades away when I back off the throttle, but reappears when the revs settle down. Is that what piston slap sounds like?

Offline BSA500

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Re: Identifying a rattle
« Reply #1 on: 14.01. 2013 21:33 »
Might not be your issue but check the carb slide isn't worn enough to rattle. Easy to check take off the air filter, if you have one, and just put a little pressure on the slide with your finger. If the ticking stops there you go. Guess who had a annoying rattle for months *conf*

Online bsa-bill

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Re: Identifying a rattle
« Reply #2 on: 14.01. 2013 22:05 »
My pushrods had a mark (ring) around two of them an inch or so down from the top, I assume they sometimes kiss the rocker box somewhere, could cause a rattle maybe
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
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Offline Goldy

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Re: Identifying a rattle
« Reply #3 on: 14.01. 2013 22:20 »
Yes I had that bill and apparently if the push rods are alloy they flex, which allows them to touch the side.
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Offline K1100

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Re: Identifying a rattle
« Reply #4 on: 14.01. 2013 23:18 »
The fact that the rattle increases under load but dies away momentarily when the load is removed seems to be important ... as if the pressure of combustion is making it worse. That's why I was thinking piston slap?

Online KiwiGF

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Re: Identifying a rattle
« Reply #5 on: 15.01. 2013 00:14 »
K1100, I've not heard piston "slap" on an A10 but I did on a GB 400 (single) Honda and it was at it's worse under full load going up hills round 3/4 max revs. Not sure if  that helps! The bike did not burn much oil it was just much noisier when it occured, not such much a rattle either as the extra noise was pretty "constant" at a given throttle setting.

If you are taking the head off and are concerned about the rattle, it might be worth taking the barrel off as well, to check the small and big ends, and rings. You can of course check the piston/barrel clearance without taking the barrel off.

PS/edit - I assume the primary chain is not too loose and causing the noise?
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Offline metalflake11

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Re: Identifying a rattle
« Reply #6 on: 15.01. 2013 01:34 »
Were the marks/rings only on the exhaust pushrods chaps?.........I'd check the carb slide too, mine started with this type of noise and my stethoscope come screwdriver told me it was the slide, and it didn't lie.
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Offline Rookie_V#60

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Re: Identifying a rattle
« Reply #7 on: 15.01. 2013 09:14 »
Hi all,

I have a similar behaviour on my A7, tried to take it on a video (sorry for the images pls take only the sound :-))

           http://www.youtube.com/watch?v=4nmUH6xnQpA&feature=plcp

The rattle is also in the head area, not in the bottom of the engine and only if I pull the throttle.

Cheers R.

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Online bsa-bill

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Re: Identifying a rattle
« Reply #8 on: 15.01. 2013 09:45 »
Just had a thought when looking at the under load comments - pre-ignition - also if it just on one side could be timing is more advanced on one side than other due to unequal maggie cam.
Easy to eliminate if you haven't got the head off yet, just retard the timing a bit and try it.

Just a random thought probably popped due to my frozen brain as I've just had he dog out in the snow, he loves the stuff, me I like it on Christmas cards
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online BSA_54A10

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Re: Identifying a rattle
« Reply #9 on: 15.01. 2013 09:50 »
Try pushing the rockers to one side with a stick it could also be the rockers sliding left right.
If that is the case you need either to replace the thackery washers with new ones ( they loose their spring over time ) or with thrust washers.
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Trevor

Offline muskrat

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Re: Identifying a rattle
« Reply #10 on: 15.01. 2013 09:53 »
 G'day K1100, does it do it straight away when cold or only when hot? Could be a loose guide when hot, or a slightly bent push rod from cold to hot.
Cheers
Just saw Trevor's post. Good point, worth a try.
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Offline duTch

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Re: Identifying a rattle
« Reply #11 on: 15.01. 2013 10:08 »

 Hiya guys,
              I haven't been around for a bit, and also laying low and trying to stay out of trouble......!
 Hope everyones' year has kicked (or otherwise..roller/'lectric../or um,bump? )started well..?

 Was wondering re Trevs' thought, what difference the rocker shims/thackeries would make  if they were in the wrong side of rockers..?

 cheers, duTch
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Offline K1100

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Re: Identifying a rattle
« Reply #12 on: 15.01. 2013 11:43 »
There's plenty to go on there, and stuff I hadn't thought of to eliminate before I dismantle anything. Thanks v. much to all. Final question ...  can I run the engine with the rocker box inspection covers off? If so that would give me another chance of listening/looking before stripping.

Offline muskrat

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Re: Identifying a rattle
« Reply #13 on: 15.01. 2013 12:42 »
 Yes you would need to, to try Trevor's suggestion. No harm will result.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
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Offline Topdad

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Re: Identifying a rattle
« Reply #14 on: 15.01. 2013 13:04 »
also a good way to check the oil flow to the rockers , covers off and you'll be cleaning oil off the engine and surrounding areas but if not ,time to worry about something else as well, best of luck BobH.
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