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1970 A65 Engine noise #2275
05/02/05 7:45 am
05/02/05 7:45 am
Joined: Sep 2004
Posts: 9
Sydney Australia
V
Victor Terry Offline OP
BritBike Forum member
Victor Terry  Offline OP
BritBike Forum member
V
Joined: Sep 2004
Posts: 9
Sydney Australia
A noise has developed in my 1970 Firebird engine,
at first I thought it was the rotor, which I subsequently replaced. The noise is a rattle that appears to be coming from the primary chaincase, I have pulled the cover off but everything appears tight. I wonder if the noise could be caused by the rubbers in the clutch, has anyone encountered this?
Victor Terry

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Re: 1970 A65 Engine noise #2276
05/02/05 12:41 pm
05/02/05 12:41 pm
Joined: Aug 2001
Posts: 4,987
Stone Creek OH USA
R
Rich B Online happy

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Rich B  Online Happy

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R
Joined: Aug 2001
Posts: 4,987
Stone Creek OH USA
The noise your hearing, does it occur at a specific RPM? Is it a noise at idle only?

A65's will make a knocking sound at idle if it has excess crank end play. Normally, you can't hear it above idle.


Life is too short to drink cheap, bad beer.
Re: 1970 A65 Engine noise #2277
05/02/05 4:07 pm
05/02/05 4:07 pm
Joined: Jun 2004
Posts: 64
Aberdeen MD
M
MikeA65F Offline
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MikeA65F  Offline
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Joined: Jun 2004
Posts: 64
Aberdeen MD
Victor Terry
After about 400 miles on a rebuild my 1970 Firebird developed a severe rattle at 65mph on interstate. Immediately pulled over and rattle went away as I reduced speed. No noise at idle. Headed home with no noise until I hit about 60mph. Pulled in clutch and noise went away. Coasted to side again and no noise at idle. I shut the bike off and looked around. Rear front fender mount had broken loose.
Good Luck

Re: 1970 A65 Engine noise #2278
05/02/05 6:10 pm
05/02/05 6:10 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

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Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,812
Seattle
Here's how I can best describe excessive crankshaft endplay noises (your biggest concern): It goes gluglunkgugkunk guguguglunglunk at idle. Very irregular and not tinny at all. Also, it tends to have a strong vibration resonance, especially under hard acceleration. Certainly, it's easy to get thrown for a curve by something unexpected. I had this tinny clanging that sounded like it was coming from the inside of the motor that was really worrying me, but when the kickstand fell off, it was gone. :rolleyes:

Good luck and cheers.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: 1970 A65 Engine noise #2279
05/02/05 11:59 pm
05/02/05 11:59 pm
Joined: Nov 2003
Posts: 70
Tracy, California
O
olgbeezer Offline
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olgbeezer  Offline
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Joined: Nov 2003
Posts: 70
Tracy, California
My'66 A65L had a similar noise..thought it was from the top end due to the frequency (Hertz) of the sound. I found while inspecting the underside of the engine with a large mirror laying under it that...the chain was coming into contact with the frame at certain loads and speeds (the bike is chopped and has a real long chain)..drove me nuts for weeks chasing internal engine symptoms....Good luck...let us know what you find.


'66 A65L original
'66 A65L "old school" chopper
Re: 1970 A65 Engine noise #2280
05/03/05 1:02 am
05/03/05 1:02 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
In Remembrance
Happy Birthday BONZO R.I.P.  Offline
In Remembrance
Joined: Aug 2001
Posts: 3,348
Michigan, USA
I had a '70 Lightning that developed a rattle that went away above idle , turned into a more pronounced knock but I couldnt locate it . Always seemed to come from the alternator area in the chaincase. My situation turned out to be a spun small end bush on the left rod . These things are so full of interesting and hard to define sounds it is all but impossible to o anything more than guess without listening to it , but some other causes I have seen and heard about for this include, a broken oil tank mount under the seat , bad primary chainwheel teeth , loose rotor nut ,even a loose oil pump side crank nut.But probably the most common cause of this that I have seen is ignition timing . Before I went with a Boyer and took measures to prevent it from slipping , it seemed to only ta ke a small adjustment problem to make my engine sound like I am getting piston slap . Probably not bad enough to do any dmage , but that sorta noise bothrs me ...-BONZO

Re: 1970 A65 Engine noise #2281
05/03/05 12:13 pm
05/03/05 12:13 pm
Joined: Feb 2002
Posts: 285
Dallas, TX
Brian_Dallas_TX Offline
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Brian_Dallas_TX  Offline
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Joined: Feb 2002
Posts: 285
Dallas, TX
LOL Alex!!!

I think Bonzo is right, kinda hard to diagnose w/o hearing it. Keep at it and you'll get it.


Brian
'64 B40T Enduro Star '49 AJS 18CS
'65 A65L/R '71 BMW R75/5
'71 B25T '02 Bonnie
'63 A10 SR
'47 James ML 125
Re: 1970 A65 Engine noise #2282
05/03/05 12:20 pm
05/03/05 12:20 pm
Joined: Sep 2004
Posts: 9
Sydney Australia
V
Victor Terry Offline OP
BritBike Forum member
Victor Terry  Offline OP
BritBike Forum member
V
Joined: Sep 2004
Posts: 9
Sydney Australia
Thanks for all your comments regarding the engine noise, I am going away for a few weeks to Western Australia but when I return I will look at all of the things suggested and hopefully it will be one of those, if not I am building up a new motor anyway.

Re: 1970 A65 Engine noise #2283
06/24/05 7:18 am
06/24/05 7:18 am
Joined: Sep 2004
Posts: 9
Sydney Australia
V
Victor Terry Offline OP
BritBike Forum member
Victor Terry  Offline OP
BritBike Forum member
V
Joined: Sep 2004
Posts: 9
Sydney Australia
I have pulled the motor down and found that the left hand piston had cracked just above the gudgeon pin on both sides, obviosly what was happening the piston was expanding and the gudgeon pin was becoming loose in the piston.
rebored the barrell to +20 and am fitting lower
compression pistons so that this will not occur again, I think that the original pistons were experiencing pre ignition, this is the cause of the crack.

Re: 1970 A65 Engine noise #2284
06/24/05 12:02 pm
06/24/05 12:02 pm
Joined: Sep 2002
Posts: 7,812
Seattle
Alex Offline

BritBike Forum member
Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,812
Seattle
FYI, I just redid my motor and polished the combustion chambers and piston crowns, eliminating all sharp corners and guess what: It doesn't ping. Even when very hot and under heavy load...no pinging on unleaded 93. I highly recommend this because the cost is low and there are no potentially deleterious effects.

Cheers,

-alex


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.

Moderated by  Allan Gill, Jon W. Whitley 


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