Series 3 Red top pattern fuel pump pressure

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So the feeling of ecstasy was short lived. But it makes sense. The removal of the screw blocking the fuel return now leaves insufficient pressure. Although it ticks over fine and no longer overflows, a test drive showed that it doesn't pull under load now. Huffing, puffing, farting, hissing and chugging to a halt (and that's just the driver!). So I've been informed that a main jet for a motorbike carb needs inserting in place of that pesky screw. Can anyone advise me on what size/ type / spec I should fit?

Cheers

P.
 
That's a good idea too.
I think the newly overhauled carbs are so efficient now that the fuel is by passing them and pumping straight back down the return and back to the tank. Path of least resistance sort of thing.
 
As above a pic of your setup may help.
As I said earlier there maybe a restriction, I also thought they were at the carb end.

SUs don't need/take much pressure.
Whatever you use make sure it cant get loose and end up somewhere it shouldn't ;).

MIG welding tip would go in that hose and you could clamp it in place;).

J
 
20240501_182438.jpg
20240501_182422.jpg

First photo shows the fuel supply in and supply off to the left to 2nd carb.
2nd photo shows supply coming over from firs carb and the return to take pipe.
 

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If you take the nut off what's sort of fitting is it. just think that may be a good place to put some sort of restriction.

J
 
Yes that's what I'm thinking. The black pipe is just that ie pipe, but I'll take another look at the thread on the other side over the weekend. I've just ordered an amal main jet off ebay for a couple of quid and hopefully work around that.
 
NowayPedro said:
Wow! That is amazing. Thank you so much for your dogged detrrmination to get to get to this. I have just got home so haven't had time to read through the whole thread yet, but to see that photo brought a broad smile to my face after a hard day! Is that a (already mentioned) mig welder tip fitted in the early stages of the return pipe I see?
Click to expand...

I have no idea. I thought it was standard issue, which was why I thought it was at the carb end.
As yours is a conversion who knows what POs did.
Maybe ask the guys who did your carbs, I can’t find that particular part.

No but the hole is about the size of a mig tip ;)

J
 
marjon said:
I have no idea. I thought it was standard issue, which was why I thought it was at the carb end.
As yours is a conversion who knows what POs did.
Maybe ask the guys who did your carbs, I can’t find that particular part.

No but the hole is about the size of a mig tip ;)

J
Click to expand...
You are a legend. I feel a pint coming on!
 
Several break downs later and finally an intermittent fault became permanent. Which helped me to detect it. So no fuel supply. Whipped out the pump, took it apart and was totally blocked up with tank rust!20240515_194355.jpg20240515_194400.jpgIMG-20240515-WA0006.jpeg20240515_194347.jpg
 
So is it now running ok now?
It could just be that since you took out the screw the return was stirring up the tank and disturbing the loose stuff.

Or was it because of the screw you were getting more fuel than you needed?

J
 
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