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Oil in cylinder but head gasket is still good--what's the deal? #261006
06/25/09 3:22 am
06/25/09 3:22 am
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
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AndrewKerth  Offline OP
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Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
This past weekend, the A50 began to stumble in mid-ride. It was a warm day, and the motor had reached proper temp some time ago.

Took it home and checked the plugs. The left one was fouled and wet with oil. Cleaned the plug and restarted the bike for a few minutes, and again the left plug was fouled and covered with oil.

Given it was wet oil on the plug and not sooty carbon, I figured the head gasket was shot...

...so I took it off.

The head gasket looks fine. Looks new, almost.

Any idea what the problem could be?




(And no, like an idiot, I didn't do a compression test first.)


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star
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Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: AndrewKerth] #261032
06/25/09 10:06 am
06/25/09 10:06 am
Joined: Jan 2009
Posts: 64
Finland
FinBSA Offline
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FinBSA  Offline
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Joined: Jan 2009
Posts: 64
Finland
Are you sure its oil, not gasoline? If its oil it comes past valve guide or piston rings, not from head gasket. There are few oil passages in gasket too, but no pressure in those, just drain holes.


BSA 650 Lightning `69
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: FinBSA] #261035
06/25/09 10:33 am
06/25/09 10:33 am
Joined: Oct 2006
Posts: 343
southern N.H.
GREEN MONSTER Offline
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GREEN MONSTER  Offline
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Joined: Oct 2006
Posts: 343
southern N.H.
Greatings from N.H. well you have gone this far and taken the head off might as well clean it all up and start by checking bores and pistons and also the condition of the head.

While you're digging into her grab the rods and feel how much play they have, chances are if they feel loose they are and check the end float on the crank.

Good Night and Good Luck Signed GreenMonster


Good Night and Good Luck Signed GreenMonster
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: GREEN MONSTER] #261075
06/25/09 2:32 pm
06/25/09 2:32 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

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Joined: Sep 2002
Posts: 7,813
Seattle
Smells of a broken or stuck ring to me.

Last edited by Alex; 06/25/09 2:33 pm.

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: Oil in cylinder but head gasket is still good--what's the deal? [Re: Alex] #261086
06/25/09 3:25 pm
06/25/09 3:25 pm
Joined: Jul 2001
Posts: 12,936
Central Virginia
Lannis Offline

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Lannis  Offline

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Posts: 12,936
Central Virginia
Yep, if you've got the head off already, a few more nuts and you can pull the cylinder and check the rings - see if they're intact, see if there's any cylinder scarring. They'd have to be passing a LOT Of oil to suddenly foul a plug ....

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: FinBSA] #261146
06/25/09 10:15 pm
06/25/09 10:15 pm
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
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AndrewKerth  Offline OP
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Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
Originally Posted By: FinBSA
Are you sure its oil, not gasoline? If its oil it comes past valve guide or piston rings, not from head gasket. There are few oil passages in gasket too, but no pressure in those, just drain holes.
Well, it looked like oil, and felt like oil, and it didn't smell like gasoline...but I'm beginning to have my doubts now...


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: Lannis] #261151
06/25/09 10:30 pm
06/25/09 10:30 pm
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
BritBike Forum member
AndrewKerth  Offline OP
BritBike Forum member

Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
Originally Posted By: GREEN MONSTER
Greatings from N.H. well you have gone this far and taken the head off might as well clean it all up and start by checking bores and pistons and also the condition of the head.

While you're digging into her grab the rods and feel how much play they have, chances are if they feel loose they are and check the end float on the crank.


Originally Posted By: Alex
Smells of a broken or stuck ring to me.


Originally Posted By: Lannis
Yep, if you've got the head off already, a few more nuts and you can pull the cylinder and check the rings - see if they're intact, see if there's any cylinder scarring. They'd have to be passing a LOT Of oil to suddenly foul a plug ....

Lannis

Yeah, I was thinking that, too, but didn't want to take off the barrels.

I did so just now, however, and the rings are lovely and move freely, and the cylinder bores are smooth and pristine...which oughtn't be a surprise, since the rings were replaced and cylinders honed probably not much more than a thousand miles ago.

I had thought since it was wet oil and not dry soot, it was not likely to be coming from past the pistons. I appear to have been mistaken in the assumption that it works that way, but I do seem to have been accidentally correct in determining that such was not the case this time.

I'm going to follow up on what FinBSA suggested, and examine the valve guides (which should have occurred to me, but didn't).

I'm starting to feel like the novice I apparently still am.



Thanks for the replies, folks! smile


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: AndrewKerth] #261232
06/26/09 10:10 am
06/26/09 10:10 am
Joined: May 2004
Posts: 3,823
Sydney Australia
B
BSA_WM20 Offline
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BSA_WM20  Offline
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B

Joined: May 2004
Posts: 3,823
Sydney Australia
If the inlet valve guides are a it worn you will draw down a considerable amount of oil during induction but it should either burn or be blown out on the exhaust stroke.

The really rough rule of thumb is
Smokey on the over run = worn guides
Smokey under load = worn rings


Bike Beesa
Trevor
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: BSA_WM20] #264518
07/13/09 8:22 pm
07/13/09 8:22 pm
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
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AndrewKerth  Offline OP
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Posts: 19
Waterloo, Ontario, Canada
Okay, apparently I'm a bonehead.

My take on a 'good' head gasket differs from that of my friend. It seems the head gasket is not in good shape, and hadn't been sealing properly before, as was evinced by dark spots on the gasket between the cylinders and to the outside.

Not having worked on anything with a metal gasket before, I thought this gasket was good as new when I saw it.

Anyway, thy surfaces (top of cylinders and bottom of head) are perfectly smooth, so now it's time to install the new gasket.

My question now is shall I just install it dry, or shall I spray some kind of gasket sealer onto it?

The only Spray-a-gasket stuff I've found is rated for temperatures up to 450 Farenheit, and that just doesn't sound hot enough to me.

Any suggestions?




(In the meantime, a thanks to all for their previous suggestions...you got me to check a lot of things that really should have been looked at. Thanks to you, I know the condition of my con-rod bearings, valve guide seals, rings, and much more. No, they weren't the problem, but it's good to be able to rule them out entirely.)


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: AndrewKerth] #264525
07/13/09 8:55 pm
07/13/09 8:55 pm
Joined: Apr 2005
Posts: 1,674
Mississauga, Ontario.
A
Adam M. Online content
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Adam M.  Online Content
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A

Joined: Apr 2005
Posts: 1,674
Mississauga, Ontario.
Use your old gasket, just heat it up to cherry red and cool it down in the water - it makes it soft again.
Check your head base and cylinder top for being straight - if not they should be machined to make them.
Mine had been, and I use only dry gasket with good results.

Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: Adam M.] #264534
07/13/09 9:47 pm
07/13/09 9:47 pm
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
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AndrewKerth  Offline OP
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Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
Well, they're nice and straight, and since I already bought the new gasket, I guess I'll use it (and hang onto the old one).

Given that the head and cylinders were just as straight last time as they are now, and gasket spray stuff WAS used, what could have gone wrong?


Should I have re-torqued the head after riding a few hundred miles, or is this generally not necessary?


You mention heating a gasket to soften it...is it possible this should have be done when installing new gaskets as well?


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star
Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: AndrewKerth] #264587
07/14/09 2:07 am
07/14/09 2:07 am
Joined: Apr 2005
Posts: 1,674
Mississauga, Ontario.
A
Adam M. Online content
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Adam M.  Online Content
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Joined: Apr 2005
Posts: 1,674
Mississauga, Ontario.
Yes, it should be done.

Re: Oil in cylinder but head gasket is still good--what's the deal? [Re: Adam M.] #264614
07/14/09 4:33 am
07/14/09 4:33 am
Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
AndrewKerth Offline OP
BritBike Forum member
AndrewKerth  Offline OP
BritBike Forum member

Joined: Oct 2008
Posts: 19
Waterloo, Ontario, Canada
Okay, then. I had not read anything about heating gaskets to soften them prior to installation.


These Haynes manuals are really good at letting people figure things out on their own.


Thanks for telling me about that. It would never have occurred to me.


"I'm just the guy who does the thing."
--Toby Ziegler (The West Wing)



1968 BSA Royal Star

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