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New Problem LOUD Backfiring #24550
05/05/07 5:48 pm
05/05/07 5:48 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
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Vox Teardrop  Offline OP
BritBike Forum member

Joined: Aug 2005
Posts: 1,145
Indy
Put 75 trouble-free miles since the rebuild on the 64' A65 and all of a sudden on Thursday night the left hand cylinder kept popping and giving a rather explosive backfire every 30 seconds or so. What I don't get is the suddenness of this problem. It's been fine until Thursday. Any ideas?


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket
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Re: New Problem LOUD Backfiring #24551
05/05/07 6:01 pm
05/05/07 6:01 pm
Joined: Oct 2004
Posts: 1,058
San Francisco
Redman Offline
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Redman  Offline
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Joined: Oct 2004
Posts: 1,058
San Francisco
Valve lash adjustment changed? Leak in intake? Points? One side loosened and changed. Head gasket leak on left side? Did you retorque yet?
Backfiring is change in ign timing or valve timing, or lean mixture. Check everything before riding again!!!


Life is short but very wide.
Re: New Problem LOUD Backfiring #24552
05/05/07 6:44 pm
05/05/07 6:44 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
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Vox Teardrop  Offline OP
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Joined: Aug 2005
Posts: 1,145
Indy
Quote:
Originally posted by Redman:
Valve lash adjustment changed? Leak in intake? Points? One side loosened and changed. Head gasket leak on left side? Did you retorque yet?
Backfiring is change in ign timing or valve timing, or lean mixture. Check everything before riding again!!!
Running Boyer and already checked plate to make sure it hasn't moved. Have not checked valve lash adjustment yet. Have not retorqued yet. Would a faulty/intermittant coil problem cause the same issue?


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket
Re: New Problem LOUD Backfiring #24553
05/05/07 6:57 pm
05/05/07 6:57 pm
Joined: May 2004
Posts: 557
Norway, just south of Oslo
J
jangg Offline
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jangg  Offline
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J

Joined: May 2004
Posts: 557
Norway, just south of Oslo
Redman's right - but ...

Some priority can be made:
1. Time lamp ignition for the sake of order. Quick and easy.
2. If point one's ok, then I would do some valve clearance check. Not too tight - and not too loose. Just Right (in case you forgot tighten the lock nuts smile ).
3. Lean mixture - different reasons. While you check the other things, just reassure yourself the carb(s) getting all the fuel they (or it) want. Make petcock give maximum that is... (dust, old dirt, anything can have obstructed the flow while you were proudly riding the monster.. cool .).


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
Re: New Problem LOUD Backfiring #24554
05/05/07 8:26 pm
05/05/07 8:26 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
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Vox Teardrop  Offline OP
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Joined: Aug 2005
Posts: 1,145
Indy
Well, I checked and cleaned the carb and that hasn't cured it.


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket
Re: New Problem LOUD Backfiring #24555
05/05/07 8:31 pm
05/05/07 8:31 pm
Joined: May 2005
Posts: 3,849
ohio
shel Online content
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shel  Online Content
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Joined: May 2005
Posts: 3,849
ohio
with the bike running spray some carb cleaner around the intake manifold and carb to see if you may have an air leak in that area


When given the choice between two evils I picked the one I haven't tried before
Re: New Problem LOUD Backfiring #24556
05/05/07 9:11 pm
05/05/07 9:11 pm
Joined: Oct 2001
Posts: 258
Monclova
S
sloppyoil Offline
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sloppyoil  Offline
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S

Joined: Oct 2001
Posts: 258
Monclova
Make sure the charging system is up to snuff.

Re: New Problem LOUD Backfiring #24557
05/05/07 9:34 pm
05/05/07 9:34 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
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Vox Teardrop  Offline OP
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Joined: Aug 2005
Posts: 1,145
Indy
Quote:
Originally posted by sloppyoil:
Make sure the charging system is up to snuff.
Voltage is excellent at 12.43 with ignition off with the brand new alternator putting out 14 volts or so @ 3000rpm.


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket
Re: New Problem LOUD Backfiring #24558
05/05/07 10:00 pm
05/05/07 10:00 pm
Joined: Aug 2001
Posts: 1,182
Altoona, Florida
Mike Carter R.I.P. Offline
In Remembrance
Mike Carter R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 1,182
Altoona, Florida
Sometimes as simple as a plug gone bad..Or wire, change around plug leads and see if anything changes ..You will find it

Seeya

Mike Carter

Re: New Problem LOUD Backfiring #24559
05/06/07 12:00 am
05/06/07 12:00 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
In Remembrance
BONZO R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 3,348
Michigan, USA
One thing to pay attention to would be when the popping/backfiring happens . Is it under acceleration , deceleration, idling,steady engine speed, steady road speed??? Could be anything from a leak at the headpipe/muffler joint(my bike is prone to this )to a dodgy electrical connection that shows up at certain rpm vibes???
Personally , I have a rather extensive list of things that have caused symptoms that you describe that have happened on my bikes over the years , and with a freshly restored project you can exepect these sorta teething pains until you and your bike get to knowin each other a little better .
FWIW-BONZO

Re: New Problem LOUD Backfiring #24560
05/06/07 6:57 pm
05/06/07 6:57 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
BritBike Forum member
Vox Teardrop  Offline OP
BritBike Forum member

Joined: Aug 2005
Posts: 1,145
Indy
Mike Carter is da man. Put new spark plugs in and the problem disappeared. Weird.


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket
Re: New Problem LOUD Backfiring #24561
05/06/07 8:41 pm
05/06/07 8:41 pm
Joined: Jan 2005
Posts: 42
North Las Vegas, Nevada
O
ondgas1 Offline
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ondgas1  Offline
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O

Joined: Jan 2005
Posts: 42
North Las Vegas, Nevada
I can't tell if that is a fibreglass tank or not. If it is and you haven't recoated the tank, you will continue to rapidly foul plugs, due to the interaction of the new gasoline with the old tank. Just a thougt


56 BSA A7SS, 67 Hornet, 65 T120, 70 T120
Re: New Problem LOUD Backfiring #24562
05/06/07 10:19 pm
05/06/07 10:19 pm
Joined: Aug 2001
Posts: 1,182
Altoona, Florida
Mike Carter R.I.P. Offline
In Remembrance
Mike Carter R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 1,182
Altoona, Florida
One of the first bikes I was trying to sort out after rebuild tore thru about 6 plugs before I finally got it right..I would continue to monitor the plugs, maybe a rich condition ..Cheers man g


Mike Carter

Re: New Problem LOUD Backfiring #24563
05/06/07 11:28 pm
05/06/07 11:28 pm
Joined: Apr 2007
Posts: 80
England
V
Velo Offline
BritBike Forum
Velo  Offline
BritBike Forum
V

Joined: Apr 2007
Posts: 80
England
One thing i found handy was a color tune plug,
swap out the plug on the offending cylinder for
the color tune plug, do they still make them?

Re: New Problem LOUD Backfiring #24564
05/06/07 11:31 pm
05/06/07 11:31 pm
Joined: Aug 2005
Posts: 1,145
Indy
Vox Teardrop Offline OP
BritBike Forum member
Vox Teardrop  Offline OP
BritBike Forum member

Joined: Aug 2005
Posts: 1,145
Indy
Quote:
Originally posted by ondgas1:
I can't tell if that is a fibreglass tank or not. If it is and you haven't recoated the tank, you will continue to rapidly foul plugs, due to the interaction of the new gasoline with the old tank. Just a thougt
Metal tank but thanks for the tip.


95' Triumph Speed Triple
72' Triumph T120
64' BSA Lightning Rocket

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