Problem and solution to fuel problem with solex b30 pse1 carb on herald 1200

[Tipidave]

I recently posted about a problem with fuel leaking from the spindle of my b30pse1 whether hot or cold and the difficulty of getting the fuel pressure right for the carb. I have now come to what I think is a composite solution to the problem which I thought I would share. I have read lots of accounts of similar issues online so I know that I am not alone. 

Firstly I started with a fuel pump that it turns out was pushing 10psi, a replacement was closer to 4 psi and it  failed after less than 30miles use... upon close inspection it I was clearly destined to fail. So even buying from a reputable source is no guarantee of a fit for purpose part.

I ended up using known good original that Colin very kindly sent and subsequently sold to me. The spring in the original was noticeably weaker than either of the two “modern replacements”. It is the strength of the spring that determines the pump pressure. The displacement of the diaphragm determines the volume of fuel moved.

I retained the filter king regulator that the previous owner had installed (presumably to help rectify the problem of having a 10psi fuel pump!) and set it to register just 1psi (knowing of course that the gauge may well be somewhat inaccurate at such a low setting) ... working on the assumption that if at high speed the combination of a smaller valve diameter(see below)and lower pressure were providing  too low a flow of fuel , then I could increase it.

Following my enquiry to Esso about the specific gravity of the fuel that I use , it seemed likely that the float was sitting lower in the fuel than it should; meaning a too high level before the valve tries to close. Modern fuel does have a lower S.G than four star of old. I managed to adjust the float a little, and set it with a second 1mm washer in addition to the 2mm thick washer under the float valve. I tried a total of 4mm but this resulted in difficulty starting. The combination of 3mm washers has weakened the idle mixture (smells different) and it starts on the button whether hot, cold or somewhere in between.

In the end, tried three float valves. And settled upon a 1.3mm rather than a 1.5 mm that had been recommended....even the third valve was still leaking although much improved.... so I ultrasonic cleaned it, tamped it home gently to help it seat, and then put some t cut into the valve and span the metal valve end by connecting it to a dremmel. This was then thoroughly flushed with carb cleaner.The combined effect of polishing it and tamping it to create a better seat seems to have worked. 
 

in combination these steps have now resolved the issue and the whiff of petrol upon cutting the engine is no more. Hope that this somewhat lengthy report might help someone else who experiences such a worrying symptom that must have been a fire risk.

Thanks to everyone who contributed ideas to my original post. Very much appreciated.

[Peter Truman]

Re your effectiveness of a  low pressure  "pressure gauge" I worked in the Water Industry for 40 years and when we metricated in the early 70's rather than going from psi to kpa we went to metres head of water, now when we changed the now old tech pressure recorders the 0 to 100psi chart was replaced with a 0 to 70mts chart, SO 1psi = 0.7mts head or 3psi = 2.1mts head etc. So to measure the delivery pressure of your pump just put a poly tube on the pump delivery and raise it to over 2mts high so fuel doesn't flow out of the end of the pipe then lower it till  fuel just flows out and that equates to your delivery pressure! The height of the end of the pipe is the critical point not the length of poly tube it could be X mts long. It won't be too messy if you start high. Oh and remove the rotar to avoid elect contacts.