HD8 Carb Leak

[Goldie]

I replaced my needle valve on both front and rear carbs. It had not been leaking before. I adjusted the carb using a ColorTune. I drove the car and smelled gas on the short drive. It was leaking around the connection between the banjo and the car bowl. I ordered new bolt and new banjo with new fiber washers. I replaced it and now it still leaks, just not as bad but still dangerous. Have the threads in the carb just worn out and will not seal? Is there a way to improve the seal on the threads into the fuel bowl? Can I send my carbs off for rebuild and get this corrected. I have not messed with the carbs in about 15 years.

 

[Dandare]

It used to be advised that new fibre washers be soaked for a while in kerosene before use...although the later ones (that are sold now) appear to be a different composition.

Danny

 

[Bob_Spidell]

The threads of the banjo fitting don't effect a seal, the washers do, and the threads shouldn't wear out. Assuming the threads or the banjos aren't somehow damaged, you can apply some pretty serious torque to them to get the washers to seal (a 13/16" socket fits nicely). The fiber washers do take a 'set,' and often need to be retorqued after a while. Are both carbs leaking? Did you replace the 'special' washers under the bolt that holds the bowl covers? Could the leak be coming from there? Are both/all three carbs leaking?

 

[Legal Bill]

This is not an unusual problem. Are your banjos connected with metal fuel lines or flexible rubber lines? If they are removable, did you remove the hose from the banjos, or do all this work with the fuel lines still attached? How did you clean the mounting surfaces for all the parts that come in contact with the washers? How did you reassemble them? The correct method is to remove the fuel lines from the banjo if they are removable, clean all mating surfaces until they are free from all debris and delaminated portions of the old gasket, test fit the banjo bolts through the banjos and into the housing and make sure everything lines up square and tightens freely by hand, and then remove the bolt and install the washers and reassemble, making sure the washers are in place and properly seated before you tighten the bolt. Then reinstall the fuel lines. If the fuel lines are permanently attached to the banjos, the banjos may not align squarely with the housing and bolt mating surfaces. Don’t try to force them to align by tightening the bolt. Square them up by applying a bit of force to the line. And obviously, any debris on the mating faces will prevent the washers from sealing.

 

[Goldie]

The threads of the banjo fitting don't effect a seal, the washers do, and the threads shouldn't wear out. Assuming the threads or the banjos aren't somehow damaged, you can apply some pretty serious torque to them to get the washers to seal (a 13/16" socket fits nicely). The fiber washers do take a 'set,' and often need to be retorqued after a while. Are both carbs leaking? Did you replace the 'special' washers under the bolt that holds the bowl covers? Could the leak be coming from there? Are both/all three carbs leaking?

Just the rear carb is leaking.

 

[Goldie]

This is not an unusual problem. Are your banjos connected with metal fuel lines or flexible rubber lines? If they are removable, did you remove the hose from the banjos, or do all this work with the fuel lines still attached? How did you clean the mounting surfaces for all the parts that come in contact with the washers? How did you reassemble them? The correct method is to remove the fuel lines from the banjo if they are removable, clean all mating surfaces until they are free from all debris and delaminated portions of the old gasket, test fit the banjo bolts through the banjos and into the housing and make sure everything lines up square and tightens freely by hand, and then remove the bolt and install the washers and reassemble, making sure the washers are in place and properly seated before you tighten the bolt. Then reinstall the fuel lines. If the fuel lines are permanently attached to the banjos, the banjos may not align squarely with the housing and bolt mating surfaces. Don’t try to force them to align by tightening the bolt. Square them up by applying a bit of force to the line. And obviously, any debris on the mating faces will prevent the washers from sealing.

New washers, new banjo fitting, and new bolt. I did not clean the shoulder where the bolt and washer fit. The leak seems to be around the bottom of the washer nearest the carb. I have new flex lines all the way from the main hard line to the front carb and the short line between. No leaks except at the rear carb. I spent a lot of time to get the length just right between the two carbs. The one sent by Moss was too long and very difficult to align the bolts into the carb.

 

[Bob_Spidell]

Older fiber washers are a reddish-brown, the newer ones I've seen are black and possibly a little thinner; I tend not to 'trust' the black ones as much.

 

[Legal Bill]

Check the inside diameter of the washers against the old. If the new washers have a larger inside diameter, they can drop down a bit and create an opening at the bottom of the fitting.