No fuel delivery....Air in fuel pipe

[johnny650]

Would it not be easier to take the manifold off.
Check it against another manifold to see if it is shorter. before trying to weld it.

No its a lot easier to measure the manifold in situ first

Sorry i dont really have the answers you need.
But one thing i have found.

If my scooters p155 me off or im in a black dog period...i walk away from them.
Leave them til i am in a better frame of mind or feel capable if doing the jobs i need to do

very good idea except I do not have the choice at the moment

see my earlier post today

i shan't be able to check this until my back stops going into spasm probably about 2x weeks time

[HxPaul]

The position of the banjo wont make any difference what so ever as it is lower than the tank exit in whatever position its in.

Correct .........but the banjo will only fit on one way .........facing out so its academic ;


So is the petrol pipe

sorry its not clear what point you are making ?...........

Please read the rest of the thread where I have explained this in n'th detail, it should be clear by now surely

Allow me to repeat it one last time .

1. The banjo will fit on the carb in any one of 4x planes ie up, down, back and forward .

2. The fuel pipe will not fit onto the banjo in any position except with the banjo facing forwards.

This means that although one can physically fit the banjo in any position it would be pointless to do so because one could not get a fuel pipe to fit due to the proximity of the mag housing and the engine mounting .

I thought it would be obvious,Scooterdude wrote that the banjo was below the tank and you agreed.I was just pointing out that the petrol pipe was below the tank as well.

[coaster]

Just reading through this post for the first time and can sense your growing frustration but I would just make the observation that you are asking a favour and getting irritated by people asking for clarification as to the exact nature of your problem wont help. This issue is crying out for a photo or two, maybe even a short video, easy enough with any smart phone. I would also suggest that you read and consider ALL responses as one of the most telling ones was the suggestion to remove the float bowl and with the petrol on and as container underneath, check that fuel flows as soon as the float is lowered and stops when it is raised. I think you will find that the air is getting in through the needle valve when the fuel is cut off and the bubble will partially disappear when the fuel is flowing. I personally doubt that the air bubbles are causing any problem. Also bare in mind that fuel will tend to flow round the outer surface of the pipe making the apparent bubble look bigger that it really is. The check with the float bowl off would demonstrate this in a minute or two.
There is a LOT of jiggling required to get the fuel rod/tap/linkage to work smoothly but it is generally very straight forward unless using some of the long range tanks but if you really cant get a smooth angle on the rod, you can use model boar prop shaft universal joints instead, of the knuckles. Good luck with it, carry on being methodical but try to keep an open mind as to the problem, don't cling to something just because it seems to fit

Colin

[holty]

if its an original manifold, not a crappy re-made one then the carb should not be too close to the mounting, or does the engine have a cylinder fitted where the inlet studs are not quite right, maybe taking the manifold off and slightly enlarging the 2 stud holes might allow you to twist the manifold away from the mounting to get the clearance your after, lambrettas can be very frustrating at times, even some new parts not fitting, its a labour of love at times, im sure a solution can be found, good luck,
holty

[johnny650]

if its an original manifold, not a crappy re-made one then the carb should not be too close to the mounting, or does the engine have a cylinder fitted where the inlet studs are not quite right, maybe taking the manifold off and slightly enlarging the 2 stud holes might allow you to twist the manifold away from the mounting to get the clearance your after, lambrettas can be very frustrating at times, even some new parts not fitting, its a labour of love at times, im sure a solution can be found, good luck,
holty

thats very good idea indeed Holty and one which I have already done .

On the previous small block 200cc cylinder it had been over-ported on the cylinder inlet and none of the 5x inlet manifolds I had would cover the port and seal properly so I took a large block GP inlet manifold and drilled an extra hole at 150cc spacing and managed to cover the port and swivel the manifold slightly. Unfortunately it still leaked .

When I am able to get a picture up you'll see how tight everything is around the carb . its just mere mm but sufficient to cause problems all round.

Eccentric engine mounts will give an extra 3mm clearance but that would not be enough. I shall weld an extension on my inlet manifold which will solve all of the problems in a single stroke ! Its the easiest and quickest solution.

The cylinder is one of those Indian aluminium 185cc kits and I suspect that the inlet manifold stud threads are not in the same position as the Italian 150cc cylinders .

[johnny650]

Just reading through this post for the first time and can sense your growing frustration but I would just make the observation that you are asking a favour and getting irritated by people asking for clarification as to the exact nature of your problem wont help. This issue is crying out for a photo or two, maybe even a short video, easy enough with any smart phone. I would also suggest that you read and consider ALL responses as one of the most telling ones was the suggestion to remove the float bowl and with the petrol on and as container underneath, check that fuel flows as soon as the float is lowered and stops when it is raised. I think you will find that the air is getting in through the needle valve when the fuel is cut off and the bubble will partially disappear when the fuel is flowing. I personally doubt that the air bubbles are causing any problem. Also bare in mind that fuel will tend to flow round the outer surface of the pipe making the apparent bubble look bigger that it really is. The check with the float bowl off would demonstrate this in a minute or two.
There is a LOT of jiggling required to get the fuel rod/tap/linkage to work smoothly but it is generally very straight forward unless using some of the long range tanks but if you really cant get a smooth angle on the rod, you can use model boar prop shaft universal joints instead, of the knuckles. Good luck with it, carry on being methodical but try to keep an open mind as to the problem, don't cling to something just because it seems to fit

Colin

Colin thanks for the response and suggestions. Yes I am getting frustrated with the problem but I'm also getting exasperated with posters that don't bother to read through the thread , see what has already been answered and understand the issue before replying with irrelevant or duplicated advice............... like removing the fuel tank cap to vent the system...or removing the fuel bowl to check the fuel flow and rate.

it would be so much easier if this could be talked through . So much more can be said than typed with one finger and it would save misunderstandings and confusion

I have already removed the fuel bowl many many many times and observed the fuel flow which is fine. ( I have been rotating 4x carburettors with different jets and slides etc)

With the bowl off and the float hanging down, the pressure of the head of fuel in the tank pushes any air out of the fuel pipe . Once the bowl is refitted the scooter will start and run normally until switched off and left for an extended period.'

This is just a temporary solution and does not help this issue .


, once air has been drawn into the fuel pipe over night no amount of pressure from the tank seems to clear the air lock. ..the engine needs to start before it can draw fuel through the fuel bowl and fuel pipe and purge the air.

Once the engine starts the air is drawn through and it runs normally. I have been removing the fuel pipe from the petcock and topping up the fuel pipe with petrol thus expelling all the air which enables the engine to start

Believe me the air is not a figment of my imagination and I find it insulting and not terribly helpful to suggest that I'm some sort of idiot that cannot see a column of air in a fuel pipe after 50+ years of working on classic vehicles . if you refer to some of the images I have posted in related threads you'll see what I am talking about .

Air-locking in fuel systems is a well known and common phenomena even in pumped systems. once the air is purged the fuel will flow and the engine will start and run fine but if the source of the air ingress isn't found and sealed the problem will just keep reoccurring indefinitely.

I cannot take pictures at the moment because I am semi paralysed stuck in a chair with constant back spasms.
As said previously when my back is better i will go back and start from scratch sorting out all the various issues like the petrol tap shaft and inlet manifold so that everything has sufficient room to function properly. I will also fit a seperate direct feed fuel bottle and test with that . When I have found the problem and solved it I'll post back with my findings and some images .

[coaster]

I've been pondering your air bubble issue and was wondering if you had checked the condition of the needle valves in the carbs you are using (you said you have several) Some needles are intolerant to modern fuel and they are now coloured red or black to denote the type (cant recall which is which). I still think this the most likely point of entry for the air so the sealing of that tip is crucial. If their was a leak anywhere in the tap then fuel would leak out, evaporate and leave a very visible oil deposit. Know what you mean about speaking rather than having a conversation, I'm sitting at home doing nothing recovering from some surgery so feel free to give me a call if you want 07775680 458

Colin

[Daggs]

It's red-tips for modern fuel. They replaced the original black tips.

(However it seems Scootopia have decided to use a black tip in their 22mm Dellorto/Jetex copy. Presumably it is suitable for modern fuel, but it does create some confusion)

[johnny650]

I've been pondering your air bubble issue and was wondering if you had checked the condition of the needle valves in the carbs you are using (you said you have several) Some needles are intolerant to modern fuel and they are now coloured red or black to denote the type (cant recall which is which). I still think this the most likely point of entry for the air so the sealing of that tip is crucial. If their was a leak anywhere in the tap then fuel would leak out, evaporate and leave a very visible oil deposit. Know what you mean about speaking rather than having a conversation, I'm sitting at home doing nothing recovering from some surgery so feel free to give me a call if you want 07775680 458

Colin

thanks Colin .....good to talk with you today. Wishing you a swift recovery so that life can return to normal.

Thanks for your advice....I'll try turning off the petrol tap and run the fuel out of the fuel bowls once I have got the petrol tap working again. At the moment I'm having to use an inline tap.
Its a good procedure to use especially when vehicles are not used frequently and fuel additives and detergents tend to clog up float needles and jets these days.

[johnny650]

It's red-tips for modern fuel. They replaced the original black tips.

(However it seems Scootopia have decided to use a black tip in their 22mm Dellorto/Jetex copy. Presumably it is suitable for modern fuel, but it does create some confusion)

I think I have a mixture of both red and black and haven't paid much attention to which I have fitted to be honest because I am rotating carbs to save time and convenience.

I probably should check the lengths of all the float needles too as I read somewhere that there are 2x different lengths which can cause fuel supply issues