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ET: Engine (Twin) 1954 Black Shadow Oil Fouling on front Cylinder only, any checks?


JohnA

Website User
VOC Member
Been through all carb settings and had it to pieces many times, I feel like I can rule that out as well as plugs. New needle/jets/float - complete rebuild.

I have reversed the ignition leads to count that out. I did a compression test to find both cylinders equal. 52lb on kick.

I'm now convinced it's oil fouling, in the picture you can see the plug looks like it's painted satin and it's wet always. I have the same plug reading no matter what I do to the carburation and I've made many adjustments. I have six plugs that look the same. Again the rear is always perfect.

I have checked for wet sumping I was thinking maybe after the lead free conversion done some time ago, someone may have used valve seal and one popped off? Or a retaining screw come loose?

If any one has any suggestions before I get seriously spannering I'll take anything before I have to take down the head!
 

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mercurycrest

Well Known and Active Website User
VOC Member
Looks like it's running too cold. If the ignition, rings and guides are all OK from your tests it can only be a restriction in air intake... Remember that wipe cloth you lost last winter? ;)
 

JohnA

Website User
VOC Member
Haha, I am going to take off the tank and have a close look, but this is how it was delivered from a very reputable man :) I am going to inspect for a blocked oil line between the rockers,
 

JohnA

Website User
VOC Member
Besides the slide height adjuster being on the other side can I just change carb bodies and keep float bowls?
 

chankly bore

Well Known and Active Website User
VOC Member
An uncommon cause can be pooling of oil around the lower exhaust guide. This can be exacerbated by the machine being stood on the left-hand propstand for a time. I've also had a head where rocker tunnel re-bushing broke through the exhaust port.
 

JohnA

Website User
VOC Member
I have done over 200 test miles so far and a number of plugs, I think I can see some oil around the intake valve where I left it closed. Manifold is a little tricky to get off so I am going to order an inspection cam which Ive wanted for years.
 

Bob

Active Website User
VOC Member
John, I had the same problem and I agree it's oil fouling. The front plug on my Rapide would foul after a few miles. I tried hotter plugs and they would go a few more miles before fouling.
I cured this by fitting new valve guides, the ones from VOC spares with the oil seals, and have had no problems since.
 

JohnA

Website User
VOC Member
John, I had the same problem and I agree it's oil fouling. The front plug on my Rapide would foul after a few miles. I tried hotter plugs and they would go a few more miles before fouling.
I cured this by fitting new valve guides, the ones from VOC spares with the oil seals, and have had no problems since.
I may still be wrong but I think this is where I am headed, I do only get smoke when I kick it hot as in when it has stalled. Kicking cold just clears the oil with the tickle and turning the motor I think. Some one has modified the rocker feed bolts - Im wondering if they also have a used seals which have gone faulty, the bike was unused for a long time.
 

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JohnA

Website User
VOC Member
Looks like oil is getting into the intake, does anyone concur? Looks like a summer stripdown - guarantee might not be applicable but I will wait for a response from seller before I dive in and discover more Vincent engineering.
 

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BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I may still be wrong but I think this is where I am headed, I do only get smoke when I kick it hot as in when it has stalled. Kicking cold just clears the oil with the tickle and turning the motor I think. Some one has modified the rocker feed bolts - Im wondering if they also have a used seals which have gone faulty, the bike was unused for a long time.
The oil seals usually do a pretty good job of controlling oil getting down the valve guides so maybe you do not have oil seals fitted or maybe not fitted correctly. Before diving in too far would it be worth trying a restrictor wire in the front inlet rocker feed bolt to see if that makes a difference?
 

JohnA

Website User
VOC Member
Will that be ok with the modified rocker feed bolts, I take it the oil passes through the old threads with this mod?
 

davidd

Well Known and Active Website User
VOC Member
That is a locking rocker feed bolt and I am not sure that the hole is big enough to get a meter wire through. The hole at the top tends to be smaller and deliver less oil to begin with. The lower feed can either be one or two holes on the first thread on the body side. The nut should not pull up tight enough to cover them.

I would guess that it is a sloppy guide in combination with no draining.
100_0396.jpg

100_0400.jpg

Not very pretty, but effective.

I would probably install a sealed guide, but draining the guide area might be effective also.

David
 

Cyborg

Well Known and Active Website User
VOC Member
The photos in post 11 look a little odd to me, but I'm not the resident expert. Maybe it just the photo, but the seat looks like it protrudes into the port more than normal. Usually just a small amount if any from what I have seen. As if the head was ported at one point and then the seat was replaced at a later date. Not that you are going to be racing it, so not worth worrying about flow, but is worth having a look at it if and when you pull the head off.
 
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JohnA

Website User
VOC Member
The photos in post 11 look a little odd to me, but I'm not the resident expert. Maybe it just the photo, but the seat looks like it protrudes into the port more than normal. Usually just a small amount if any from what I have seen. As if the head was ported at one point and then the seat was replaced at a later date. Not that you are going to be racing it, so not worth worrying about flow, but is worth having a look at it if and when you pull the head off.
Interesting,. I will most likely take the head off and get some expert to look
 

Sakura

Well Known and Active Website User
VOC Member
Why strip a bike in the summer? Oil fouling on the front cylinder is a well known Vincent fault. Fit a hotter plug, use the bike for the summer and repair over the winter.
 

JohnA

Website User
VOC Member
If I do manage to find a plug to cope I'd be surprised but leave it until September and I won't have any chance of guarantee not that I've had an email reply from the vendor yet. But things like this niggle me, just knowing something's wrong.
 
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