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Smoking LH Cylinder #483803
03/31/13 6:22 pm
03/31/13 6:22 pm
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
TriVin Offline OP
BritBike Forum member
TriVin  Offline OP
BritBike Forum member
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
My 72 Bonnie has done 600m since having a rebore. It has continually oiled up the LH plug since then so I assumed that the rings had not seated properly on the LH cyclinder.
However, upon pulling it apart today I found that the LH inlet valve outer surface was smothered in oil and the other 3 all nice and dry. Upon removing all the valves I could see that behind the LH inlet valve again was much more oily than behind the other 3.
When I had the rebore done I had all 4 valves replaced as the stems were undersize and the exhaust guides replaced as they were a rattling fit but left the inlet guides alone as they were a nice slide fit and still are.
So the question is, am I confusing myself?
If oil is getting past the LH rings because of not bedding in properly would I be correctly seeing oil around the inlet valve and not the exhaust valve purely because it is not as hot around that area?


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
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Re: Smoking LH Cylinder [Re: TriVin] #483857
04/01/13 12:08 am
04/01/13 12:08 am
Joined: Nov 2005
Posts: 7,379
Back on the mainland!
JubeePrince Offline

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JubeePrince  Offline

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Joined: Nov 2005
Posts: 7,379
Back on the mainland!
Originally Posted By: TriVin

If oil is getting past the LH rings because of not bedding in properly would I be correctly seeing oil around the inlet valve and not the exhaust valve purely because it is not as hot around that area?


Hi Dave,

If the oil is getting past the rings on the drive side, and they're not bedding properly, I'd expect to see a glaze on that cylinder...any evidence of that?

Sounds to me like oil is finding its way past that drive-side inlet valve/guide...are the specs correct?

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Smoking LH Cylinder [Re: JubeePrince] #483915
04/01/13 9:58 am
04/01/13 9:58 am
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
TriVin Offline OP
BritBike Forum member
TriVin  Offline OP
BritBike Forum member
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
Hi
No glazing on the cylinders. I can see the cross hatching from the honing clearly. Both cylinder bores look identical.
I don't have the equipment to measure the bore of the guide but I know the valve stem is correct and the fit is a 'nice slide fit'. That is a subjective term I know but as I am a retired toolmaker you will know that I know what I mean!!!
The guide could be leaking through it's fit into the head itself I suppose or maybe a crack in the same area? I can't see anything obvious though. Is there a pressure test that could be done to check that out. I remember people talking about using paraffin or kerosene in the old days for checking the valves for seating properly but I'm not sure how you would use that to check for anything else.


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
Re: Smoking LH Cylinder [Re: TriVin] #483917
04/01/13 10:59 am
04/01/13 10:59 am
Joined: Sep 2011
Posts: 977
New Zealand
Excalibur Offline
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Excalibur  Offline
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Joined: Sep 2011
Posts: 977
New Zealand
They can also leak down the head studs, into the inlet port. There's been alot of talk about this on the forum so a few suggested fixes as well.

Also well worth looking at is the upgraded head stud washers for the nuts inside the rocker boxes.

Re: Smoking LH Cylinder [Re: Excalibur] #483925
04/01/13 12:12 pm
04/01/13 12:12 pm
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
TriVin Offline OP
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TriVin  Offline OP
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Joined: May 2006
Posts: 148
Warrington, Cheshire, UK


I forgot to post a picture of what I saw when I removed the head.
Seeing this you would naturally think it was the valve guide.
I have read up about the problem of oil getting down the bolt holes and I did use the larger head bolt washers. Although I thought that this problem manifested itself by oil getting into the combustion chamber via the head gasket. I should say that my head gasket was sound and showed no signs of oil getting across. And of course I would expect the whole of the chamber to be wet with oil rather than just the valve head?
I can see when looking into the inlet valve chamber that there is a sleeve or bush of some kind for the middle head bolts that breaks through into the inlet chamber and is obviously intentional??? Can this be a potential source point for oil to get into the valve chamber?


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
Re: Smoking LH Cylinder [Re: TriVin] #484075
04/02/13 3:02 am
04/02/13 3:02 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
Originally Posted By: TriVin

Seeing this you would naturally think it was the valve guide.

I can see when looking into the inlet valve chamber that there is a sleeve or bush of some kind for the middle head bolts that breaks through into the inlet chamber and is obviously intentional??? Can this be a potential source point for oil to get into the valve chamber?

It probably is from the valve guide,but not from stem-to-guide clearance.It's more than likely leaking between the guide and the head,because the hole is damaged and scored.Also check that there is no chamfer on the top of the guide bore,acting as an oil reservoir.

I've never heard of any problems with the sleeve in the intake port.

Re: Smoking LH Cylinder [Re: Pete R - R.I.P.] #484110
04/02/13 9:23 am
04/02/13 9:23 am
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
TriVin Offline OP
BritBike Forum member
TriVin  Offline OP
BritBike Forum member
Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
Hi Pete
No chamfer on the bore of the guide only the OD. I remember, I think, you recommending a larger chamfer on the OD in order to stop ANY oil gathering on the top surface. Don't have a lathe but could probably achieve this using my bench grinder, after a fashion!!
Do I also remember you using a high temp silicon under the head of the guide? Or was it the little O ring on the valve stem or both?
Anyway, I'm going to get the head cleaned up and replace the inlet guides anyway then at least I'll know all 4 are new.
I'll check the condition of the guide holes before I get the new guides in case I need oversize ones which seem to be readily available.


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
Re: Smoking LH Cylinder [Re: TriVin] #484113
04/02/13 9:51 am
04/02/13 9:51 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
I always fit 010 viton O-rings in the top spring collar before I put the collets in.It can stop a little bit of oil draining down the stems.

If the stem-to-guide clearance is OK,sealant around the guide can help in cases where the hole in the head is scored.
If you blast the guides clean before removal,there's not much chance of scoring the head.Too often,this isn't done.

Drilling the guide to thin the walls can help too.There's less pressure on the guide when you punch it out.Don't drill all the way through;leave a shoulder to punch against.Heating the head is almost useless when you remove guides.

Re: Smoking LH Cylinder [Re: TriVin] #484118
04/02/13 12:24 pm
04/02/13 12:24 pm
Joined: Jun 2010
Posts: 37
queensland
K
kye Offline
BritBike Forum member
kye  Offline
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K
Joined: Jun 2010
Posts: 37
queensland
Pretty sure I can remember someone here saying
You shouldn't leave bike on side stand for too long or this will happen
No experience just read it

Re: Smoking LH Cylinder [Re: Pete R - R.I.P.] #484262
04/03/13 2:19 am
04/03/13 2:19 am
Joined: Nov 2005
Posts: 7,379
Back on the mainland!
JubeePrince Offline

Life member
JubeePrince  Offline

Life member
Joined: Nov 2005
Posts: 7,379
Back on the mainland!
Originally Posted By: Pete R
It's more than likely leaking between the guide and the head,because the hole is damaged and scored.


Hi Pete,

How could this happen, exactly? Unless I mis-read Dave's original post, he only replaced the exhaust guides not the inlet ones...unless you're saying the oil is originating from the replaced exhaust guide?

Sorry, I'm spatially-challenged sometimes! Just curious....

Cheers,

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...

Moderated by  John Healy 


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