8 replies to this topic

[steve1978]

I’ve done a little video so hope this works. Thank you so much to all of your help so far
As title says there is a bit of fuel on top of a carb.

https://sendvid.com/zvh1ogba

Edited by steve1978, 16 April 2024 - 12:49 PM.

[bpirie1000]

Does your carbs have an overflow. Either a pipe from the top of the float or a metal plate that goes over the feed with the overflow under the feed..

The movement in the float is not an issue. Just a bolt between the carbs on the body of the float. Should become evident when you have a look at it....

I trust you have removed the float and made sure it is working and that the feed is stopped when the float is at it's highest point.....

They sometimes get stuck or something sticks it and fuel continues to flow, hence the overflow and carb being wet...

[steve1978]

Does your carbs have an overflow. Either a pipe from the top of the float or a metal plate that goes over the feed with the overflow under the feed..

The movement in the float is not an issue. Just a bolt between the carbs on the body of the float. Should become evident when you have a look at it....

I trust you have removed the float and made sure it is working and that the feed is stopped when the float is at it's highest point.....

They sometimes get stuck or something sticks it and fuel continues to flow, hence the overflow and carb being wet...

I have not. I’m really new to this. Last time I had a cr with a carb was 96, I didn’t touch that one either! I will do some readership on carbs and come back to this. Just want to make sure that it’s actually safe to use.

[Chris1275gt]

If it’s an su carb the bolt next to the cotton bud tightens the float chamber to the carb body and no petrol can leak out of there. It looks like the float lid is loose are the 3 screws tight and does it have a gasket? If the valve is letting petrol by and there isn’t a overflow pipe the top of the chamber has a small hole open to atmosphere where it will leak out of.

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Edited by Chris1275gt, 16 April 2024 - 04:38 PM.

[nicklouse]

I’ve done a little video so hope this works. Thank you so much to all of your help so far
As title says there is a bit of fuel on top of a carb.

https://sendvid.com/zvh1ogba

You in Aus? 
 

it coming out of the overflow. Look at the float height and condition and also the chamber needle valve and seat.

[steve1978]

 

I’ve done a little video so hope this works. Thank you so much to all of your help so far
As title says there is a bit of fuel on top of a carb.

https://sendvid.com/zvh1ogba

You in Aus? 
 

it coming out of the overflow. Look at the float height and condition and also the chamber needle valve and seat.

 

No, I’m in Liverpool region, uk. 
 

I’ve watched some vids on you tube now about the su carb, I now understand how the float works and what could be wrong. I think the gasket might be the issue. 
 

if I open it up can I do any damage to it? Doesn’t need anything changing to get the flows right? I’m thinking take the lid off, check the gasket, check float moves, measure the float height then reattach.

[Lplus]

If the fuel is on top of the float bowl lid I don't see how the gasket can be at fault.  Far more likely the needle valve is leaking and fuel is escaping from the shrouded overflow hole beneath the inlet pipe.  I suppose even vibration and a worn needle valve might be enough to allow a minor leak.

 

Just as a very unlikely possibiity, check the inlet rubber pipes are sealing properly on the brass inlet pipe and the inlet pipe itself is tight in the float bowl top.

 

If you can get the top off the float bowl without damaging the gasket it can be reused.

 

The float bowl may have a rubber anti vibration washer between the float bowl and carb base. This allows the float bowl to move slightly relative to the carb.

[coopertaz]

from video fuel seems to be from gasket as top of flot bowl looks dry. re movement there is a rubber mount between body and float bowl that sets the bowl angle this could be in need of renewal but can be tightened up by bolt on underside of carb. although this may require carb removal on your twin set up to get access

[Tornado99]

My single HS4 SU carb was leaking onto bowl top like you are reporting. First thing I thought of, the rubber tipped float valve needle, as these can deteriorate with age and with ethanol fuel. MiniSpares sells an all brass float valve seat & needle which should be ethanol fuel proof. Also good to change all rubber fuel hoses, carb to tank, if not ethanol rated (usually have printing on the hoses stating ethanol safe). 

Fitting the new valve and a new bowl gasket, still had the leakage onto top of bowl. Dried it, started the car and kept a careful look at the carb top for a minute or two....sure enough I saw fuel escaping around the top to bowl sealing joint, even with a new gasket. Seems the top may have become warped, possibly from someone over tightening the three fastener bolts. The metal is soft and can deform with too much torque on the bolts. Replacing the top with a new one should fix, but I tried  one last thing...a fuel proof flange/gasket sealer product from Locktite...513 I believe...applied both sides of gasket. Goes on a bit like red jam. Immediately solved the leaks and has been fine for more than 1 year now. 

Edited by Tornado99, 19 April 2024 - 09:31 PM.