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Posts: 164
Joined: August 2001
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Joined: May 2020
Posts: 1
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OP
Novice poster
Joined: May 2020
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My ‘69 A65L suddenly experienced issues with hard starting and rough idling and running. Carburetors, timing, etc. checked-out OK.
On closer visual inspection I noticed oil bubbling out from the top of the nut on the right front cylinder stud onto the head, something I’d never seen before.
It must be coming up the stud bore from below. Nut was tight. I visually checked the flange between the head and the cylinders and didn’t see any sign of leakage there. I then checked compression: 125 ft-lbs on right side cylinder, 100 ft-lbs on left (opposite side from leaky nut).
Is this a head-gasket issue or could it be something else? How does the oil get up there? Does it cross the head gasket from the oil return tube to the base of the stud or what? Any advice on what I should do next before I remove the head?
Thanks,
Paul Stuverud
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Joined: May 2013
Posts: 7,567 Likes: 94
Britbike forum member
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Britbike forum member
Joined: May 2013
Posts: 7,567 Likes: 94 |
The compression is low on both Cylinders for a engine with 9:1 pistons. Was this checked on a warm engine with throttle fully opened, and readings taken after 1 kick then after a second kick?
If you didn’t have the leak I’d suggest verify your valve gaps. You don’t want anything tighter than 0.008” inlet and 0.010” exhaust. Going tighter will start giving rough idle (from experience when I thought I’d try it and see what happened)
As you have the leak I’d remove the head, remove the 4 studs and check that the cylinder face is flat, also check the cylinder head. Too many people plane the head without considering the barrel. Re-anneal the gasket or use a new one and anneal it.
Now let’s all have a beer  68’ A65 Lightning “clubman” 71’ A65 823 Thunderbolt (undergoing restoration) 67’ D10 sportsman (undergoing restoration) 68’ D14 trials (undergoing transformation)
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Joined: Jan 2014
Posts: 1,213 Likes: 81
Britbike forum member
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Britbike forum member
Joined: Jan 2014
Posts: 1,213 Likes: 81 |
The head gasket is blowing, time to take the head off i'm afraid.
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Joined: Aug 2001
Posts: 5,481 Likes: 49
Britbike forum member
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Britbike forum member
Joined: Aug 2001
Posts: 5,481 Likes: 49 |
The oil leaking up around the stud is a common problem with A65s, since the oil drain holes from the front valve wells go through the head gasket. The oil makes its way across the head gasket and over to one or both studs. This doesn't in itself cause running problems, but a failing head gasket may also be causing a loss of compression. Bottom line though, as NickL said, time to take the head off.
Mark Z
'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
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Joined: Jan 2014
Posts: 1,213 Likes: 81
Britbike forum member
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Britbike forum member
Joined: Jan 2014
Posts: 1,213 Likes: 81 |
A popular mod is to fit small o-rings into the head gasket on the oil ways when fitting.
As Allan says make sure both surfaces are flat first and anneal the gasket.
I tend to use a drop of welseal on the gasket but that's just 'cos ii'm old fashioned.
Don't forget to re-torque the head after it has been used for a few hundred miles, i
know it's a pain but it's worth it.
Nick
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