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A65 head torque check after rebuild #563262
09/14/14 6:41 pm
09/14/14 6:41 pm
Joined: Jul 2012
Posts: 398
Fergus, Ontario, Canada
D
Dave T Offline OP
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Dave T  Offline OP
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Joined: Jul 2012
Posts: 398
Fergus, Ontario, Canada
How many miles do folk typically put on a rebuilt engine before checking the torque on the head and cylinder base nuts?
I just checked mine after 50 miles and they did not need adjusting so I am wondering if I should have put more miles on it? Only thing I did find was an inlet valve clearance that had closed up! Did not seem to stop it running but it is correct now. I know that no clearance on exhaust valves can burn the seats but what happens if the inlet side is closed up?
Dave

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Re: A65 head torque check after rebuild [Re: Dave T] #563267
09/14/14 7:12 pm
09/14/14 7:12 pm
Joined: Jan 2006
Posts: 3,330
Medford, Oregon
Gary E Offline
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Gary E  Offline
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Medford, Oregon
Did you loosen and re-torque or just check the existing torque tightness? I put a mark on the bolt head/nut before checking torque.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
Re: A65 head torque check after rebuild [Re: Dave T] #563269
09/14/14 7:27 pm
09/14/14 7:27 pm
Joined: May 2004
Posts: 3,743
Sydney Australia
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BSA_WM20 Offline
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Sydney Australia
It is not the number of miles that is important.
It is the number of heating and cooling cycles.
Normally with A 65's only a few will be required as there are no external push rod tubes to sort out.

The head heats up and becomes too big for the space between the nut & the barrel so it either causes the bolt to stretch a little or the alloy to compress a little ( it actually extrudes from under the nut or collapses into the stud hole for the nit pickers who feel the desire to remind us of elemental physics ).
It will also cause the copper head gasket to deform for the same reason.

So when everything gets cold and contracts you get insufficient clamping pressure to maintain a gas tight seal.
On an A 65 usually once will be enough.
I have put engines together that never needed retorqueing and others that never really settled down.
Cylinder base gaskets should relly not need retorquing as the paper is very thin to start with.

And you don't "check" the torque on the head bolts.
You back them all off about 1/4 turn and retorque them.
Once the engine has cycled a few times the torque required to move the nuts will be substantially higher than the actual torque on the bolt ( called the breaking torque ).
If you have a ratchet or deflecting pointer torque wrench you will see that oft well over 30 ft/lbs is needed to loosen a nut done up to 20 ft/lbs


Bike Beesa
Trevor
Re: A65 head torque check after rebuild [Re: Dave T] #563272
09/14/14 8:00 pm
09/14/14 8:00 pm
Joined: Jul 2012
Posts: 398
Fergus, Ontario, Canada
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Dave T Offline OP
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Dave T  Offline OP
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Joined: Jul 2012
Posts: 398
Fergus, Ontario, Canada
Thanks for the information about backing of and retorquing. I did not do that, I just set the breaking ratchet to 30 and checked it did not move the bolts. Season is so close to ending hear that i think I will use what good weather is left to ride it and do the job again during winter shutdown!

Re: A65 head torque check after rebuild [Re: Dave T] #563311
09/15/14 7:37 am
09/15/14 7:37 am
Joined: May 2004
Posts: 3,743
Sydney Australia
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BSA_WM20 Offline
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Sydney Australia
Sounds like a plan.
just to be on the safe side try to avoid large throttle openings at lowish rpms.
This puts the greatest compression pressure on the cylinders so just keep it spinning freely and Robert should be you mothers brother.


Bike Beesa
Trevor
Re: A65 head torque check after rebuild [Re: Dave T] #563332
09/15/14 10:43 am
09/15/14 10:43 am
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

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Posts: 7,813
Seattle
FWIW, I stopped retorqueing BSA unit twin heads a long time ago. Never got any purchase out of it, never had a failure.


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: A65 head torque check after rebuild [Re: Dave T] #563358
09/15/14 1:40 pm
09/15/14 1:40 pm
Joined: Jan 2006
Posts: 3,330
Medford, Oregon
Gary E Offline
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Gary E  Offline
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Medford, Oregon
I too have had very few that showed a re-torque was needed. The exception was the Spitfire I rode at the I. Rally. It was re-torqued prior to the rally. Two bolts moved past the mark very slightly.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
Re: A65 head torque check after rebuild [Re: Alex] #563363
09/15/14 1:46 pm
09/15/14 1:46 pm
Joined: Jul 2001
Posts: 12,841
Central Virginia
Lannis Online content

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Lannis  Online Content

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Posts: 12,841
Central Virginia
Originally Posted By: Alex
FWIW, I stopped retorqueing BSA unit twin heads a long time ago. Never got any purchase out of it, never had a failure.


I talk myself into not doing it because I hate pulling the rocker arm shaft just to check torque that doesn't really need re-setting .... !

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: A65 head torque check after rebuild [Re: Lannis] #563364
09/15/14 1:53 pm
09/15/14 1:53 pm
Joined: Sep 2005
Posts: 5,963
NL
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Ger B Offline
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Ger B  Offline
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NL
I'm going to have to do it...
It's one of those things... when you do it you find it was not necessary.
When you don't you may end up hating yourself when the gasket releases oil.

It's not the rockershaft I hate to remove. It's the uncertainty about the four nuts around the spark plugs.
I usually did them by hand, with just as much force and lever as on the bolts with the torque wrench...


Ger B

Re: A65 head torque check after rebuild [Re: Ger B] #563384
09/15/14 4:53 pm
09/15/14 4:53 pm
Joined: Feb 2007
Posts: 2,234
Atlanta, GA USA
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Semper Gumby Offline
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Posts: 2,234
Atlanta, GA USA
I will be re-torqing the Lightning Rocket head here in a bit. I want to look at the new push rod I put in any way.

I will prolly do it at 50 miles at the first oil change.

No leaks so far (knocks on wood).

Last edited by Semper Gumby; 09/15/14 4:55 pm.

Gaggle of BSAs
a Honda
an old BMW
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Re: A65 head torque check after rebuild [Re: Dave T] #563386
09/15/14 5:03 pm
09/15/14 5:03 pm
Joined: Oct 2007
Posts: 1,537
Auckland NZ
Ignoramus Offline
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Posts: 1,537
Auckland NZ
Lannis said "I talk myself into not doing it because I hate pulling the rocker arm shaft just to check torque that doesn't really need re-setting .... "

Got to say I agree there . I did A65 head gasket around 15k miles ago and haven't touched it ...mind you I did get the head trued and barrel skimmed a few thou so knew everything was dead flat.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 head torque check after rebuild [Re: Dave T] #563639
09/17/14 7:23 am
09/17/14 7:23 am
Joined: Apr 2005
Posts: 2,383
Bega NSW Australia
Mark Parker Offline
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Mark Parker  Offline
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Posts: 2,383
Bega NSW Australia
I just do them the once, though putting a spanner on the outer 4 is easy enough. I just put the head back on my thing tonight, after having the cyls re-plated. It should have 11-1 comp now rather than 12.3 I didn't realize I was using before. I don't use a base gasket so tappets don't move much, I check them after a few thousand miles but rarely after that.


mark

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