10 replies to this topic

[Se7enS1ns]

Hey all,
Got a set of twin 1.5'' su's, and one of them seems to have sprunk a leak from the top of the float bowl lid, just above the brass pipe fitting.
Theres a little cover over it, so ive removed this to find a hole behind it. It doesnt look like theres ever been a bung there, so just wondering if this is supposed to be there, as some sort of float bowl pressure relief maybe?

They weren't leaking before the engine rebuild, and only seem to leak when spinning the engine over, but not idle.

Any ideas folks? Failing that, anyone got a lid without the hole they can send me?

Cheers,
Dan

Edited by Se7enS1ns, 23 September 2007 - 12:45 PM.

[Ethel]

It's an air vent, without it the carb wouldn't work at all well.

If there's petrol coming out of it the carb has flooded - check the float 'n float valve.

[Big_Adam]

Seconded!

Check the needle valve...or just grind them in like I do.

[Se7enS1ns]

It's an air vent, without it the carb wouldn't work at all well.

If there's petrol coming out of it the carb has flooded - check the float 'n float valve.

Ah is it really? I didnt know that, but yeh that would make sense i guess! Thanks for that. It just seems a bit strange as it an almost new set bought from Minispares, never been stripped or anything, yet the lids on the pair are different. Shouldn't the other side have the same?

I wont worry about the leak too much then at the mo, i'll see if it settles down once the engine beds in a bit, like i say it only seems to do it on persistant turn over when trying to get it running. Im guessing the fuel pressure is blowing past the float and out the breather.

Thanks both!

[Ethel]

I'm sure both will have a vent somewhere. If the carb is flooding it would also cause difficulty in starting the car. What fuel pump are you using?

[Big_Adam]

I still stand by my "grind the valve in" trick. Takes 10mins to do and could save you twiddling with the pressure.

~Hell you can grind the damn thing in using toothpaste. Infact thats how the old guy at Westgate told me how to do it. Used to work at BMC, nice chap.

[ginigwunkle]

whats this grinding?

[Se7enS1ns]

I still stand by my "grind the valve in" trick. Takes 10mins to do and could save you twiddling with the pressure.

~Hell you can grind the damn thing in using toothpaste. Infact thats how the old guy at Westgate told me how to do it. Used to work at BMC, nice chap.

Seconded - Care to share your wisdom? Ive never ground a needle valve in before, i am assuming you mean the needle valve not the float pin valve?

Also, it doesnt seem like the carb mouth is flooding, its still relatively dry when lifting the dash pot piston and having a feel, so it doesnt seem like the carb its self is flooding as such, just leaking at the breather.

[Se7enS1ns]

I'm sure both will have a vent somewhere. If the carb is flooding it would also cause difficulty in starting the car. What fuel pump are you using?

Just the stock mechanical pump. The engines up and running (of a fashion) now, so i dont think it was actually causing the carb to flood as such, just fuel to pee out of the breather you pointed out.

Thanks again, much appreciated!

[Big_Adam]

whats this grinding?

Seconded - Care to share your wisdom? Ive never ground a needle valve in before, i am assuming you mean the needle valve not the float pin valve?

Yeah, the needle valve in the float lid.

Take the float lid off and drift the pin for the float out. Keep the float and pin to one side. Then remove the needle valve. Comes in two parts. A plastic and metal inner with some sprung flat end and a pointy end. Point end goes into the tube nut thingy to make a seal when the float is up.

Remove the tube nut thingy from the lid of the float and mount that in a drill chuck. Then pop some toothpast/valve grinding paste/t-cut into the tube nut thing and then put the other half of the needled valve in. Using some needle nose pliers hold the end of the inner part of the valve and spin the drill so the nut tube bit spins but the other half dosen't. Spin that for a bit, add a little pressure if you like. After a while (long or short as you like, the needle pointy bit is harder than the nut tube bit) take the inner part of the valve out and check it over. Then take the whole lot out and scrub it with some white spirit and make sure it's clean.

Next take a wee fiber washer and put this on the threaded end of the tube nut thing and put the whole lot back together. With the float lid still off the carb flick it upside-down and blow into the fuel inlet and see if there's a leak. If not then put it all back togther.

Cost around £2 to do as you'll prob need a new float gasket and a wee tiny fibre washer. If your pressed for parts the float top gasket can be replace with cereal box card. Only as a temp measure and the wee fiber washer you can probably get for free from a local nut and bolt shop.

[Se7enS1ns]

Aaahh i'll give that a shot, cheers!