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Leaky Carb's


Sprocket5

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Sprocket5

After a recent long run in my SEi (1.6 CVH) I found that there was petrol dripping from the bottom of the carb's (weber 40's)

On further investigation I noticed that both carb's were slightly loose and that I could easily turn all of the fixing nuts.  

Anyone know what torque should I apply to retighten the fixings.

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Mark_Knopfler

Hey, don't panic.

My 40's weep a little petrol too. Sometimes can be quite damp at the bottom of the filters.

There are a number of nut's and bolts on the top of the carbs which appear to be loose. Most noticably on the choke fitting.

Also notice how your engine oil smells of petrol?    Open the filler cap and take a good sniff.  Petrol?

Well, I was told it's because the twin 40's pump loads of fuel in,  in fact too much for the cvh to burn off, making it over carburrated.  Therefore some of the petrol ends back where it came from and some ends up heading back into the engine where it condenses and mixes with the oil I think.

Eitherway it seems to happen on all CVH with 40's I've ever seen.

Cheers,

Mark

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Mark Stanton

Don't overtighten your carbs - they need to be mounted on the "loose side".

It may be that you need to renew the mounting "rubbers" - they sit in a ring and can perish after a time.

I have same set-up and they used to "weep" but after replacing the mounts and a good tune-up to ensure everything was fine - no more "weeps"

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Blatman

Fix the weeping as Mark says, by replacing the Misabs and the thackery washers. Leaking fuel is not good......fuel in the oil is not good either. There are implications for the big ends/crank longevity, as well as the possibility of "bore wash", if you have fuel running into the engine that isn't being burnt.

I did, and it cost me a strip/hone/rebuild to fix :( Not cheap on a Cossie.........

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Sprocket5

Thanks for the comments.  Looks like I need to get some new mounting rubbers.  I note that the carbs need to be on the "loose side" but how loose is that?  I can actually move mine very slightly in relation to the engine!

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just check the fuel is not leaking from around the trumpet where it slides inside the carb body this is quite common usualy happens when they need a tune + service

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Blatman

How loose is loose? Depending on the length of your trumpets, you are aiming for between 5mm and 10mm of movement at the trumpet. Is the shorter te trumpet, the less movement you will see.

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