Pietje precies Posted July 20, 2019 Report Share Posted July 20, 2019 Hello there Each time after driving a tour there is a leakage under the front carburetor. The rear carburetor remains dry. We leave the car outside the garage for some hours and after that we push the car inside. We do not start the engine The next morning the air in the garage is filled with fuel damp. The doors of the garage in front and rear are set open all day. After two days the smell of fuel is low. The stops in the top of the float chamber are renewed and the hoses from float chamber to carburetor too. The leakege comes from above the nozzle adjust nut. What can cause this leakage ? Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 21, 2019 Report Share Posted July 21, 2019 Fuel height , the jet with the red base is not sealed to its holder if fuel is too high it runs out the jet and dribbles down the clearance between jet and its holder and drips off the red elbow Its a needle valve amd float hight problem Pete Link to comment Share on other sites More sharing options...
Pietje precies Posted July 21, 2019 Author Report Share Posted July 21, 2019 OK I understand it. Bit how can I solve it? By turning the idle screw up? I do not like adjusting the carburetor, because the enigine runs well now. Piet (pronounce like Pete) Link to comment Share on other sites More sharing options...
chrishawley Posted July 21, 2019 Report Share Posted July 21, 2019 Hi Piet, A good diagnosis from Pete. The fuel will leak from the jet if the petrol level in float chamber is higher than the bridge of the carburetor body. This leakage will tend to be most apparent on slow running or with the engine just switched off because under load conditions the float chamber is being continually drained by the engine's requirement for fuel. How to fix it? The root of the issue is fuel level too high in the float chamber. Three common reasons for this: 1) Needle valve in float chamber worn and therefore not cutting off fuel entry when the float chamber is full. Solution; replace valve 2) Float itself is faulty. Can be cracked (fills with fuel) or worn where it acts on needle (insufficient lift) or for float with adjustable metal tabs the tabs are bent to too low a position: In essence; replace float. Needle and float replacement can be done without removing the carb from the or upsetting the mixture adjustment. Obtain replacements from a reputable source (e.g. Burlen, Moss) not eBay cheapies. 3) An third and additional reason is replacement of the standard fuel pump with one that pumps at too high pressure and defeats the needle valve in one or both carbs. Hope that helps. If you want more detail than this do post again and I can fill in some of the finer details if required. Regards Chris Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 21, 2019 Report Share Posted July 21, 2019 Amd to add if the hoses have been fiddled with there a good chance you have made the dreaded rubber slivers caused by pushing hose onto metal pipes small bits get cut off the inside of the hose They float about and cause chaos jamming in the back of the float valves Pete Link to comment Share on other sites More sharing options...
Pietje precies Posted July 22, 2019 Author Report Share Posted July 22, 2019 Thanks for the answers. Although I am very busy now (painting the whole house at in- and outside) I will take a look at the float chamber first. Piet Link to comment Share on other sites More sharing options...
Pietje precies Posted July 27, 2019 Author Report Share Posted July 27, 2019 Today I saw that the front float chamber is almost empty (1cm fuel left) The rear float chamber is filled normally. So I think that the problem is in the carburetor. There should be a leakage at the front jet or something like that. Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 27, 2019 Report Share Posted July 27, 2019 Check the leak is not from the olive 0 ring where its seated in the base of the float chamber , it could run down the tube and drip off the red elbow Pete Link to comment Share on other sites More sharing options...
Pietje precies Posted July 28, 2019 Author Report Share Posted July 28, 2019 The O-rings have been replaced last year. That part and the hoose are dry. The leakage comes from above the screws for needles adjust. Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 28, 2019 Report Share Posted July 28, 2019 A bit odd , if the level was low it wont spill out the top of the jet , there is no seal between the jet and its holder/adjuster as fuel in general should not be in that area, Has the red elbow fractured??? Pete Link to comment Share on other sites More sharing options...
sulzerman Posted August 1, 2019 Report Share Posted August 1, 2019 Don't adjust the idle screw, you will upset the balance of the carbs! Link to comment Share on other sites More sharing options...
Pietje precies Posted August 10, 2019 Author Report Share Posted August 10, 2019 Yesterday I took some time for the Spitfire. I measured a difference of 2 mm in the adjustment of the idle screws. Maybe this causes the fuel leakage. I tuned the front idle screw upward until the same adjustment of the rear carburator idle screw. After having started the engine en kept it running until the temp meter was rising and then I stopped the engine. There was some fuel smell in the garage. This morning this was not present anymore. Is this THE solution ?? Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 10, 2019 Report Share Posted August 10, 2019 That nut adjusts the jet height relative to the air piston needle by turning it up you have weaken the mixture on the carb. The idle is controlled by the screw on the body which act as a stop for the throttle spindle Adjusting the jet upwards will have some effect on the leakage mostly if the fuel bowl levels are too high The jet that moves with the nut is not sealed . Whilst the mixture was out of balance compared to the rear carb , you have just made the mixture leaner , not solved the fuel height problem, I suggest there is a float needle problem , the needle platform on the float can get worn lightly and ridges jam the needle valve From closing properly as do debris in thebfuel supply which jam in the back of the valve Hope that helps Pete Link to comment Share on other sites More sharing options...
Pietje precies Posted August 19, 2019 Author Report Share Posted August 19, 2019 Pete I agree with your technical explanation. Never adjust the idle screw when the engine runs fine. But after having adjusted the front idle screw the is no fuel lekakage present anymore. Maybe that some vibrations caused the idle screw to turn into the lower/wrong position. Let's wait and see what happens. Lats weekend we had a ride with the Spitfire and I noticed no direct negative at the engine. It ran as usual ( I think) Piet Link to comment Share on other sites More sharing options...
Pietje precies Posted August 29, 2019 Author Report Share Posted August 29, 2019 After 2 rides (1 of 250 km and one of 140 km) the Spit engine ran fine. After 2 weaks no fuel leakage and also no smell of gas anymore. This winter I think to do a basic adjustment of the carbs as written in the manuals. Thank you all and much fun with your Triumph. Piet 1 Link to comment Share on other sites More sharing options...
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