Misc: Carburettors Annoying 289 Carburettor Leak

Bill Thomas

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VOC Member
Comet with brass/bronze carb body which appears to be all original.. Same problem. Not cured by all (three) new fibre washers on the carburettor., including the large on directly i contact with the carburettor body.
Petrol weeps from the very top of the large flange which screws into the bottom of the carburettor body. I gather that the thinking is that the float chamber level could be too high. Fitted a new tap because the tap itself was leaking, so that possible reason is eliminated..

Any updates on a cure please.
Have you tried twisting the carb on the stub. Just a little to alter the float height.
 

LoneStar

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If the leak is at the upper edge of the union nut (E on illustration), it's either

- escaping from the opening in the carb body just above that edge
- escaping past the large fiber washer between the union nut and the jet block

The first indicates the fuel level in the float bowl is too high (leaking float valve, tilted carb) as the normal level is below the hole

The second would be a poor seal at the washer, despite it being new. Are the surfaces on which it rides (jet block and union nut) undamaged? As an earlier post suggests, a smear of Hylomar on the washer might help.
 

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nigsey

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Had the same problem on my twin 276 rear carb, it flooded every time I put the taps on, so on advice I fitted an additional fibre washer between the banjo connection on the float bowl and the Mixing Chamber Union Nut. This lowered the float bowl level by a few though and seemed to cure the problem. Curiously though, the front carb leaks fuel significantly when I tickle it and keeps running until I start the bike whereupon it stops and stays that way even when I stop the bike and leave the fuel on. I think the carbs are a law unto themselves.
 

Bill Thomas

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We built a Comet for a friend, And rather than put the petrol tank on,
I just left the top off the float chamber and filled it by hand, Just to get it going and check things.

Then we built a Twin for another friend and I tried to do the same !!, Didn't work right this time !.
After a few start ups, I found the feed to the rear carb' would only work if I flooded the front carb',
Because of the way the pipes run, These were the old standard Carb's.

Another thing that has already been said, For "Poor 1 " Best to get a centre stand,
Because when put on the side stand the float is upset !, On Old Standard carb's.
 

poor1

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I think I've fixed it thanks to all the suggestions received.
A combination of tilting the float chamber and a gentle bedding in of the float valve with silver polish seems to have cured it. I would put my money on the lowering of the float chamber.
It will still weep when the float chamber if flooded but that is to be expected, but it does not weep when the engine is running.
It was a first time start up after a lot of work on the engine for about three years and it fired first time. Need to sort the wiring out now because although the lights are working and the ammeter is showing a discharge when the lights are on and there is no movement of the needle with the engine running so I am not getting a charge, but I'm not surprised because I have rewired it and I may have the polarity the wrong way round.
On the subject of petrol leaks it would not be tolerated in todays motor vehicles. Ask yourself whether you have ever had a fuel leak on your car or modern motor cycle other than on the lines maybe. It's a wonder more of these old bikes have not gone up in smoke.
PS: I do have one of those excellent Dave Hills stainless steel centre stands. Bless his heart he was so helpful..
The only other observation I have on these Vincents is the uncomfortable riding position for anyone six foot tall. The footrests are far too high and my knees are way above the tank and the legs bent at far too acute an angle and no adjustment for height.
 

Bill Thomas

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Yes I bought a house once, And the old owner said how Warm it is in the Garage !!!,
The House Boiler was in the Garage !, It did worry me , But I always checked things were right,
After parking in there,
This went on for some years, Then a knock on the door !,
The Gas man wanted to check my boiler, It's in the garage I said,
Wrong thing to say !,
The Bastard shut my boiler OFF,
And yet I still see new Houses having Boilers in the Garage, Strange.
 

poor1

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Non-VOC Member
Lots of gas boilers are installed in garages attached to houses. Not quite the same, but at the Gas Boards insistence when I moved my gas meter, they insisted it should be installed in the garage because it was the nearest point to the outside of the property.
Some of these guys are a law unto themselves. With apologies to any VOC members in this profession.
 

Bill Thomas

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VOC Member
Lots of gas boilers are installed in garages attached to houses. Not quite the same, but at the Gas Boards insistence when I moved my gas meter, they insisted it should be installed in the garage because it was the nearest point to the outside of the property.
Some of these guys are a law unto themselves. With apologies to any VOC members in this profession.
Funny thing was. He never came back to check.
Cost me a new boiler. Which was put in the house.
I should have just turned it back on.
And took his silly sticker Off.
 

nigsey

Well Known and Active Forum User
VOC Member
I think I've fixed it thanks to all the suggestions received.
A combination of tilting the float chamber and a gentle bedding in of the float valve with silver polish seems to have cured it. I would put my money on the lowering of the float chamber.
It will still weep when the float chamber if flooded but that is to be expected, but it does not weep when the engine is running.
It was a first time start up after a lot of work on the engine for about three years and it fired first time. Need to sort the wiring out now because although the lights are working and the ammeter is showing a discharge when the lights are on and there is no movement of the needle with the engine running so I am not getting a charge, but I'm not surprised because I have rewired it and I may have the polarity the wrong way round.
On the subject of petrol leaks it would not be tolerated in todays motor vehicles. Ask yourself whether you have ever had a fuel leak on your car or modern motor cycle other than on the lines maybe. It's a wonder more of these old bikes have not gone up in smoke.
PS: I do have one of those excellent Dave Hills stainless steel centre stands. Bless his heart he was so helpful..
The only other observation I have on these Vincents is the uncomfortable riding position for anyone six foot tall. The footrests are far too high and my knees are way above the tank and the legs bent at far too acute an angle and no adjustment for height.
You won’t hear me complain about the height of the footrests, I’m only 5ft 6” and shrinking and so they’re perfect for me, I just need a stepladder to get on the bike.
 

Bill Thomas

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VOC Member
You won’t hear me complain about the height of the footrests, I’m only 5ft 6” and shrinking and so they’re perfect for me, I just need a stepladder to get on the bike.
I am over 6 feet and have used rear sets
Since about 1975.
I can hardly ride with standard rests.
 
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