- Fri Sep 30, 2016 6:28 am
#6750
My 1996 Classic 535cc has an OEM tap (IKOV). I now discover that the flow rate through this tap is just 200ml/minute, and the seal is cracked so I must replace it. But if you are riding fast, let's say at 65-70mph (at ~3800rpm, yes, its a tuned motor with 19T gearbox sprocket) and need to accelerate past a truck or bus and you open the throttle, the tap can only supply fuel at the rate of ~29mpg. So the float chamber slowly empties and the engine looses power. Maybe that’s why plug chops at full throttle are always near-white, whether I use any of my set of main jets ranging 200-260 (32mm Amal Mk2).
Above is my new push-pull+reserve tap (bought from our hosts recently). Note the different tap centre. The upper part (left, with the lever) has a cylindrical core ~4.8mm OD whilst the lower part (right with spigot nut) has a conical core maxing 4.4mm OD. In an old version of the tap that I have (bought recently at a jumble sale so it's a bit worn), the cores of both halves are identical and both are conical.
Now notice the unused corks (below, both from our hosts) with their original bags - on the left from Nov 2013 and on the right from Sept 2016. The left hand ones have 4.8mm holes whilst the right ones have ~3.6mm holes - but the part numbers are the same (09).
The new tap contained corks of the 2016 style and both joints leaked, even after soaking the corks in oil for 2 days (as suggested) and despite leaving them to soak-up petrol for half an hour or so. Using the 2013 corks, the upper section did not leak but the lower still did – and then I noticed the cork there was bunched up – presumably because the hole wasn’t large enough.
So the hole in the cork is critical – it must be ~5mm diameter not ~4mm diameter.
In fact, though, as the image shows, in both cases the cork quality is poor, with cracks that eventually flake when subjected to the push-pull movement.
As a result I have used cork gasket material, two layers x 2mm thick, each with 5mm holes - and the tap barely leaked (tests of the material in petrol show it is impervious to fuel). But once I had smeared cake soap on the seals (I have tried all the other so-called leak fixes incl. vaseline, grease, oil), neither seal leaks. Finally I have a good flow through my tap with no leaks!
Above is my new push-pull+reserve tap (bought from our hosts recently). Note the different tap centre. The upper part (left, with the lever) has a cylindrical core ~4.8mm OD whilst the lower part (right with spigot nut) has a conical core maxing 4.4mm OD. In an old version of the tap that I have (bought recently at a jumble sale so it's a bit worn), the cores of both halves are identical and both are conical.
Now notice the unused corks (below, both from our hosts) with their original bags - on the left from Nov 2013 and on the right from Sept 2016. The left hand ones have 4.8mm holes whilst the right ones have ~3.6mm holes - but the part numbers are the same (09).
The new tap contained corks of the 2016 style and both joints leaked, even after soaking the corks in oil for 2 days (as suggested) and despite leaving them to soak-up petrol for half an hour or so. Using the 2013 corks, the upper section did not leak but the lower still did – and then I noticed the cork there was bunched up – presumably because the hole wasn’t large enough.
So the hole in the cork is critical – it must be ~5mm diameter not ~4mm diameter.
In fact, though, as the image shows, in both cases the cork quality is poor, with cracks that eventually flake when subjected to the push-pull movement.
As a result I have used cork gasket material, two layers x 2mm thick, each with 5mm holes - and the tap barely leaked (tests of the material in petrol show it is impervious to fuel). But once I had smeared cake soap on the seals (I have tried all the other so-called leak fixes incl. vaseline, grease, oil), neither seal leaks. Finally I have a good flow through my tap with no leaks!
