30 replies to this topic

[Catteeclan]

The cap on the breather should be a filter not sealed, the fuel in the bowl needs to be open to atmospheric pressure for a carb to suck fuel or their would be no pressure difference in the venturi to draw the fuel through the jets.
Swap them pipes and try it just to shut me up, feel free to stick your tongue out at me if I'm piddling up the wrong tree.

Think you're bang on, I've made this mistake, can't remember which bike now.

[Studley Ramrod]

Going back to your pic that looks like a breather pipe connects directly above the fuel connection, double check you are connected to the right one.

It's one of those daft mistakes that are easy to go blind to being so close together and only get picked up with a different pair of eyebollocks.

Another trick is to use a small pipe and blow up the offending port and see where the air blows out from, looking at Dap's float height pic I recon it's a breather that links to the valve on the side of the carb body (which I think is an air cut off activated by the pressure in the CV top but can't quite remember what for).

Failing all that there must be a split in the body between those ports somewhere.

I was going to mention that next. It has been done before and iirc fuel pissed out all over the place.

[dablik]

The cap on the breather should be a filter not sealed, the fuel in the bowl needs to be open to atmospheric pressure for a carb to suck fuel or their would be no pressure difference in the venturi to draw the fuel through the jets.
Swap them pipes and try it just to shut me up, feel free to stick your tongue out at me if I'm piddling up the wrong tree.

 

Hang on a sec if i'm reading right (after a 13 hour shift) the filter should be inside the fuel line at the T it connects to on a 3vd, and the line connected to the second T is the overflow and is open..

Anyone confirm......studs/daps ! it's beginning to sound like the lines are mixed up maybe. Fook Dave might just be your not in a fuzzy cloud this morning and it's only 06.27 mucka 

Gonna get my 3vd carbs out over the weekend and have a look see.....you need any photo's mech ?

[Snowbird]

Different filter Dabs, I'm meaning the big lumps they tend to stick on breather pipes these days to keep petrol fumes out of the air, the used to be an open pipe in the good old days then the yanks started dropping lead and using a better grade of carcinogen instead so decided on breather filters.

[dablik]

Different filter Dabs, I'm meaning the big lumps they tend to stick on breather pipes these days to keep petrol fumes out of the air, the used to be an open pipe in the good old days then the yanks started dropping lead and using a better grade of carcinogen instead so decided on breather filters.

 

Ah yep, the pennies dropped now i've had a kip mucka, know exactly what you mean..

[Mechengine]

Snowbird,

 

I believe you are correct, and I wouldn't stick my tongue out at anyone. If my replies sound like that I apologize. I last time worked on the bike was 12 years ago and  I had cleaned the fuel tank because I used a fuel additive (Sta-Bil) which was supposed to prevent the fuel from going bad. Don't believe it and surely don't use it. It wrecked the fuel system. Turned everything into "red goo" tank, carbs, fuel lines etc. To the point of this long story the line I must have reversed the lines 12 years ago. I have reset the floats using a clear tube, 6mm above the centerline as per manual yes the manual says 7.4 ~ 8.4mm but my eyes are old and I had rather err on the short side after all I have been through. Unfortunately now that I have it plumbed correctly and the floats set it will not start, it back fired twice but smells flooded. I pull the plugs and take a gander.  I'm still looking for a vent hose to put on the ventilation line to the carb, do you know if it is supposed to a a check valve like the ones that attach to the top of the carbs by the air inlet boot from the air filter. Thanks for your help, I will drop an update a little later. Hopefully it will be a successful one. 

[Mechengine]

Gentlemen,

 

She lives again and does not piddle petrol all over the ground.  I would like to thank Studley Ramrod, Dablik, DapleB and Snowbird. Snowbird your keen eye to the picture I posted showing a vacuum plug on the fuel inlet led to the resolution to the problem. I had the fuel and vent hoses crossed, those have been sorted and the steed is up and running. I have some more tiding up to do then off for a test ride. Thank you again.

[dapleb]

Excellent news. What a relief. Excellent observations SB. Jobs a carrot.

[dablik]

Woopwoop very good, cor blimey Dave, well spotted fella, you've just saved mech more endless hours of frustration 

[Snowbird]

It was this pic that clinched it for me.

Although the wrong side of the carb the bosses on the side give the positions of the passages away, the one at the top (bottom in situ on bike) is clearly inline with the float valve outlet and the one below has a passage in the casting that aims for the breather outlet in the float bowl and one that aims for the diaphram valve on the side so had to be atmospheric pressure air, I'm assuming the one with the plug in front of the inlet is an unused carb heat passage.

For fuel to come out that hole it had to be a pipe mix up or something else leaking fuel and venting into the same breather.

I have to confess it's the first time I've seen a float valve setup like that as I've never had the carbs off mine yet, I did see them briefly when I had the airbox off for something but not yet had any reason to mess with them.

Thats the joy of old school engineery stuff, you can look at it (or listen) and get a good idea what's wrong without having to plug something in and decypher a fault code.

And as said it was connected years ago so when you look under the tank years later you assume it was right and go blind to it.

I shall duly accept my smug points and go and revel in my acute smuggery with a few beers in the pub this afternoon. And tonight I shall do it again just in case I made an arse of it the first time.....

Important thing is it's sorted for the right price.

Edited by Snowbird, 01 July 2022 - 01:56 pm.

[Studley Ramrod]

A pint of Smuggeroony whilst indulging in your smuggery then SB   I agree, problem sorted at zero cost, result.