Ariel Owners Motorcycle Club

Gents

After a run and stopping the engine, on attempting to restart, the carb drips a heap of fuel. This is regardless of turning the petcock off after stopping the engine and regardless of tickling the carb. The petcock is turned back on when attempting to restart and it fails miserably to start. I think it is being flooded?

I have since found that on draining the fuel via the bowl plug and then restarting, there is no dripping fuel and the bike starts. I previously overhauled the float needle, polished it and the seat in the float bowl, and checked the level with a tube inserted into the bowl plug. It was about level with the pilot air screw. I think the float needle is sealing OK, but perhaps the fuel level is a tad too high, escaping via the overflow, thus the dripping/flooding/non-starting.

Since then I have added another fibre washer above the float mounting point boss so hopefully that will reduce the fuel level a little and stop the dripping/flooding and cure the problem.

Does all of this sound as if fuel level is/was too high and if so can this affect hot start? Weirdly, on cold start I see no dripping fuel and it starts fine. Why is this?

Note - I have also added a 6.5mm teflon spacer to the long flanged intake. Can't think this will make any difference to fuel height as it's all relative between bowl and mixing chamber, but happy to be proved wrong!

Cheers

Mark

HI I would look at the float and needle and maybe put a thicker washer under the needle

I think the needle and seat may well need re-visiting. Not sure what you mean about a thicker washer under the needle. No washers present on the needle. Pretty sure the float bowl - bottom feed - seat cannot be adjusted either.

The thicker washer goes between the float bowl 'banjo' and the big nut on the bottom of the carburettor.

I replaced the upper of the two fibre washers in this picture with a dowty washer, which drops the fuel level by a couple of millimetres.

Simes - yes indeed. As per first post, I have already lowered the fuel level with two fibre washers. I'm more convinced it is simply leaking past the needle/seat despite my best attentions to both. It's not a great sealing mechanism. A little careful lapping with fine grinding paste and a light tap afterwards perhaps?

Sorry, missed that. The design is not great - a bit of engine vibration seems to help. The carburettor on my WNG is a lot better when the engine's running - it doesn't leak so much!

Seriously though, tapping the needle very lightly helps, brasso seems to help as well. You need a very good seal between the big nut and the body of the carburettor as that's another leak path. I've also taken pains to make sure that the spring clip on the top of the float is pulled up away from the float to push the float down - those clips get squashed which raises is the fuel level.

Have you got the "proper" washer (large dia) between the Large nut and the jet block to ensure the necessary seal? The fuel level should be just below the Needle jet top surface. Make sure the small dia recess in the Bowl cover is deep enough to not impede the needle movement upwards. If the bowl seat is worn enough you should get a new Bowl as it's near impossible to repair it. Your Carby is suitable for an aircleaner. Make sure the Jet block is suitable One large hole near the Intake side to match the body. Leaning the bike towards the Right will cause flooding. Nev

IF the float has a leak or is heavier it won't have the right Buoyancy either. Check action with the cover removed. You can always FIX this type of Carburettor. Nev

Simes - I'll have a go at lapping the needle into the seat with fine grinding paste and then tapping and rotating the needle. Big nut - pretty sure that is OK. I think there is a fairly recent washer in there. Spring clip - If squeezed together laterally it pushes the float down a little and grips better in the needle groove. Already done....Mine is soldered to the brass float.

Nev - as above for the washer. Thanks for the level indicator. Not sure how you can see it though. I was told level with pilot air screw or top of big (union) nut. Bowl cover recess - yes indeed, I was going to check that out - clean it and the top of the needle up. No idea if the bowl seat is worn, I'll lap it with the needle and test. No air cleaner fitted, bike has no side stand so doesn't lean when stationary. Float appears OK - it seems to rise quickly when fluid is introduced. Fixing is easy, finding what I ought to fix is not so easy.

Thanks for all the replies - all useful stuff.

nevhunter wrote: Sat Jul 12, 2025 2:36 amThe fuel level should be just below the Needle jet top surface.

That depends on your definition of "just below." My definition would be that it is "quite a bit below." The first photograph shows a hole in the jet block that's at the top of the slot used for registering the two components.
The next photograph shows the jet block after it has been withdrawn, and with the needle jet showing the location of the hole with respect to the top of the jet.
If the fuel level is any higher than the bottom of the hole, it will leak from the carburetor.

The final illustration of the the internal configuration of the carburetor shows that if the fuel level is any higher than the bottom of the Primary Air Inlet, it will leak from the hole shown above.