Moss Motors, Ltd

Following the install of my gas tank and a surprisingly easy start after 6 years of immobility from the previous owner I discovered the

rubber washers on rear carb float chamber were leaking (quite strongly), as well as leaking out of the front carb jet valve (few drops per second) .

I rebuilt the carbs with the moss replacement kits. Due to a little confusion 2 of the 4 quark gland washers were soaked for ~30 hrs and the other 2 soaked for ~6 hrs. Being impatient I reassembled and installed the carbs, and found that my front jet was dripping a few drops per minute and the rear jet was pouring.  So I let another set of the quark soak for 3 full days, installed ...and,   No immediate leaks but over the course of a few hours the contents of the rear float chamber will leak out through the gland washers of the jet valve, and the front jet although not dripping does collect some moisture.

Car is 58 mga SU-H4 carbs.

Quark has been soaked for more than enough time.

Jet valves are all new, springs and all

I'm confident that assembly is correct

What am I missing ?

 

 

You might find some useful tips here until you hear from someone else.

http://www.jcna.com/library/tech/tech0006.html

Hi

  it might not be the little seals in the jet. The larger rubber seals that seal the float chamber feed to the carb where it attaches to the throttle body can leak if overtightened or the little steps are folded over. Looks like  a leak from the jets. Did this myself a few weeks ago. Took them off and reset the seals, then tightened the bolts with gas in the bowls until the leaking stopped. It has worked for the moment.

 

Hope this helps

    Mark

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1958 MGA coupe ( under restoration
1972 MGB GT
1995 Ford Bronco
2004 Pontiac GTO

OK , i'm lost , I can find nothing wrong with my setup and yet the gas leak from the jet valve persists. I am positive the leak is from the jet and not from the float chamber.

To recap

I've done a complete cleaning and rebuild using the moss replacements, The jet valve is 100% new. All cork has received a good soak in oil, and I'm confident everything has been reassembled correctly. The one questionable part would be whether the jet locking nut is tight enough or not, but I have it as tight as it can be until it obstructs the piston above, so I'm assuming I can't tighten this anymore.

I've had some issues with moss replacement parts not fitting with some of my original parts. Because of this I thought that maybe the cork wasn't manufactured to the correct size, but like I said the entire jet valve is a new replacement and would image many users complaining about this.

Today I've removed the rear carb (the one thats leaking more) , and before removing it notice that if you try to wiggle the jet side to side the front carb felt a lot tighter than the rear. On both jets however, as you move the jet gas would leak more strongly.  I can't find anything wrong with , threads, seals, springs, etc.

 

Please any insights.

Thanks

Sannyasi - While others have had good success with the cork jet seals, I have never been able to get them to seal properly. In the search to get the leaks to stop, I found three things that contribute to the leaking.  1) The cork jet seals - even if soaking in oil gets them to stop leaking, leaving the car undriven for long periods for long periods can cause them to dry out and start the leaking all over again.  2) The large, Jet assembly seal, also cork, can start leaking and the fuel will drip off the end of the jet fork just like it does if the jet seals leak.  3) If the screw that hold the jet fork in place (yes, I did say screw) becomes loose, it will leak fuel from the bottom of the jet.  The following are the steps that I took to stop the leaks from the carburetor jets on out TD.

1.  I removed the screw and fork from the bottom of the jets and  and cleaned the threads on the screw and in the jets, then applied LockTite to the screw threads and reassembled the fork to the bottom of the jets.  When doing this it is imperative that the the jet not be cut, scratched or deformed or it becomes junk that will leak even worse - padded pliers or vice to hold the jet while removing the fork are the order of the day.

2.  Remove the jet assembly nut and replace the cork seal with a 2-211 'O' ring.  Us of some Sil-Glide on the 'O' ring before installing it will make everything fit together easier.  Both the 'O' ring and the Sil-Glide cam be purchased from NAPA.  Using the 'O' ring in this position will make centering th ejet a bit more difficult, but with a bit of patience and some colorful words, it can be accomplished. 

3.  Finally, toss the cork 'O' ring jet seals, call Tom Bryant at 207-443-6338 and purchase some teflon 'O' rings from him.  You will need 2 'O' rings for each seal position or a total of 8 for the two jets and you will have to insure that there are no burrs or sharp edges anywhere on the jets that will damage the 'O' rings during installation, but once in correctly, you will not have any more leakage from the jets.  Don't be tempted to use the standard  'O' rings available at NAPA for this application, they will swell after a short exposure to the fuel and you won't be able to pull the choke on.  Even the 'O' rings made from viton, which is supposed to be impervious to fuel will swell (it just takes longer) and no amount of silicone lubricant nor any other exotic lubricant.  Get the Teflon 'O' rings and take the 2 steps above and you will have leak free jets.

 

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Cheers,
Dave
http://homepages.donobi.net/sufuelpumps/