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MG Midget and Sprite Technical - fuel leaking into K&N

1973 midget
1430cc Stage II engine
Weber 45
Facet pump & filter king regulator

Ok, the Midget is still in the garage & has failed the local Spanish MOT again.
All is ok apart from the fact that a tiny amount of fuel is leaking into the air filter.
They have tried bypassing the filter king regulator but no change.
The Weber has been rebuilt recently.

It's actually done this for a long time. Occasionally on tickover in traffic I get a flash from the bonnet. Never worried me the Weber spitting fuel, but the MOT guys don't share my view.




Mallorcaben

Very simple the needle valve in the carb float bowl is faulty. Either replace or perhaps the floats are not floating and are not closing this valve.
Robert (Bob) Midget Turbo

its got a new needle valve, new float assembly etc etc.
The garage it's in are a race specialists (but here in Mallorca!)
He cant seem to stop it.
I will pass on your message though Bob, thanks.

Mallorcaben

hi, I,ve got a 1275 with a stage 2 head and a 40 weber with trumpet socks on and i have the same problem, I too have ignored it, it's passed it's mot with this problem, maybe they are a little less fussy over here.I'd be interested to know if you solve it, cheers.
paul sewell

yeah, it's passed previous years but they just wont pass it.
All seems ok till its been ticking over a few mins. As soon as they smell fuel, they fail it. coņos. lol
Mallorcaben

Chuck an SU on there for your MOT with one of those nice sheet steel air filter boxes. Then swap it back to the Weber when you have your ticket.
Ben Brown

If the Weber is spitting fuel back from the rams that's not the same as a leak. Spit back can be from a very radical cam on low rpm or incorrect ignition timing (probably incorrect cam timing too).

Your car's engine does have a very shallow air filter and assumedly short rams inside it which won't help.
Daniel Thirteen-Twelve

Try Viton tipped needle valves and make sure that the float heights are correct. Also be sure your fuel pressure is no more that 2.5 / 3.0 psi

Good luck,
Mark.
M T Boldry

I didn't see any mention of spitting back Daniel?
Not sure I agree with your synopsis of how spitting back occurs, I have always found it synonimous with a weak mixture? do you not agree?

However

Please Ben and Paul it must be leaking because excessive fuel is entering the carb. That is solely controlled by the valve and float nothing more nothing less!

Occassionally if the carb is not mounted using the correct technique then vibration can cause the valve to shake open and allow excessive fuel in, could this be contributing?
Bob Turbo Midget England

Bob, very first post - 'never worried me the Weber spitting fuel' which is a contradiction of a fuel leaking.

I'd be interested to know which it is and has it been actually witnessed occuring or just the results of one or the other.

Spitting back is usually poor timing. There is something called 'stand off' where you get fuel air mixture hanging around the carb intake - one reason for having long trumpets, though I've not seen this myself.

I've not seen a fuel leak like this myself and must agree it has to be needle valve not fully closing off for whatever reason.

I have seen a dribble of fuel from the back of the carb, near the cold start device.

Perhaps we can see some fresh photos of where the full is leaking or spitting from.

I still maintain the filter and thus the rams are a lot shorter than ideal by a long way.
Daniel Thirteen-Twelve

Yep now re read and seen spitting and flashing under the bonnet.

That is totally different to leaking I agree.

However I am different to you in so much as that to me is a pure and simple weak mixture IMO normally occuring on pilot jets especially on very fine throttles. Hasten to add just my opinion.
Bob Turbo Midget England

This thread was discussed between 20/10/2010 and 24/10/2010

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