Old Amal 89 Fuel leaking from pilot air hole

[Bleng]

Hi everyone. Post 2 from my '49 model 18 rebuild.

After the 2nd road test of the AJ, I stupidy left the fuel tap open (it was late, I was tired, and I am used to a modern bike with no taps ). The next morning I went into the garage to be greeted by the smell of petrol, a big damp puddle under the bike and an almost empty fuel tank.

It looks like the fuel is leaking out of the hole opposite the pilot air valve screw (See attached photo). Would this likely indicate that the float is set too high in the float chamber, or a bad seal on the float needle? Or are there other possibilities?

PXL_20230714_091302014.jpg

Everything in the carb (stamped 89B/1AK) seems in good condition - nothing obviously worn. The float is a plastic replacement rather than the original brass one, with the needle set on the lower position. This means that adjusting it lower would be difficult, but I have just got my hands on an old brass float / needle which looks like the height has much more adjustment on.

[SPRIDDLER]

My initial thought is that the float needle isn't sealing on its seat.
It may help if you lap in the needle seat with Brasso or similar metal polish.
However, I would've thought that if it wasn't sealing the bike would run over-rich.
According to the AMAL website the needle's lower groove is correct for the plastic float, the upper one is for when a copper float is used.

[Mollbhan]

Seems little doubt the float needle is leaking, sometimes just starting the engine, the vibration will dislodge the speck preventing the needle from sealing. In theory you should not have to turn off the petrol every time, in practice I always turn off.

[1608]

Was the bike left on the side stand over night. Float may simply have got stuck before closing. I have had problems with plastic floats ( mono bloc mind) and successfully replaced with brass.

[Bleng]

Thanks all and sorry for the delay in replying. The comments all make sense to me. The bike was left on its rear stand (I have no side-stand for it yet). I've now got the carb off as I'm working on the head again.
I have replace the plastic float and needle combination with an early brass float and needle combination. Initial testing (with alcohol in the float chamber and the carb feed hole covered with a finger looks promising. No drips from the base of the float chamber (it is a bottom fed chamber).
Hopefully this will solve the problem once the bike is reassembled again.

[Mollbhan]

I had a very worn 89 carb on my 1948 mod 18 and sent it to Draganfly for overhaul and resleeving,they did a great job it came back like new. The old pre monoblock carbs however are messy and not as efficient as the monoblock, the cost of the overhaul is not much different to the cost of a new monoblock, as I use the bike rather than just look at it I would probably have been better with a new carb.