10 replies to this topic

[Charlie333]

Simple question hopefully. On the attached image, the float chamber lid has two hose fittings, what is the second one for and what do I need to do with it? Also on the main body, does the hose fitting need to go to the breather on the tappet chest cover.

 

Thank you in advance

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[alex-95]

The other pipe is for the overflow, there should be a metal pipe on the wok clutch cover and you put a bit of rubber pipe from the overflow to it so petrol doesn't run down the carb onto the hot exhaust.

The lid needs to be fitted 120 degrees away from the carb.

[Charlie333]

That makes sense, thank you

[panky]

The other pipe is indeed for a connection from the crankcase breather, usually the ones on the gearbox or timing chain cover - or you could just block it off with a piece of fuel pipe and a bolt.

[Dusky]

The other pipe is indeed for a connection from the crankcase breather, usually the ones on the gearbox or timing chain cover - or you could just block it off with a piece of fuel pipe and a bolt.

No it's not for that, its the fuel overflow.

No, you can't just block it without making sure the engine can stll breath and the crancase gasses get pulled out somehow.

[panky]

I mean the one on on the carb body - not the one on the top of the float chamber. sorry for the confusion.  The OP asked about this too.

[Charlie333]

The other pipe is for the overflow, there should be a metal pipe on the wok clutch cover and you put a bit of rubber pipe from the overflow to it so petrol doesn't run down the carb onto the hot exhaust.

The lid needs to be fitted 120 degrees away from the carb.

 

For the overflow, how much does it overflow and why? Also if it is prone to overflowing should I not return this fuel back to the tank, i'm design my own so wouldn't be difficult to put a fitting for a fuel return.

[alex-95]

 

The other pipe is for the overflow, there should be a metal pipe on the wok clutch cover and you put a bit of rubber pipe from the overflow to it so petrol doesn't run down the carb onto the hot exhaust.

The lid needs to be fitted 120 degrees away from the carb.

 

For the overflow, how much does it overflow and why? Also if it is prone to overflowing should I not return this fuel back to the tank, i'm design my own so wouldn't be difficult to put a fitting for a fuel return.

 

It shouldn't overflow normally, a sticky float needle valve or a split float will make it overflow. It's not worth sticking a return on as it'd be a fixable problem.

[Ethel]

Don't block the extra float pipe. It does serve as an overflow but its most important function is to feed atmospheric pressure to the float chamber - it's the pressure differential between the chamber and the jet that makes the fuel flow.

[Charlie333]

Thanks everyone for your help, this is my first post and i'm very impressed with how helpful people are on this forum

[Spider]

One of our lovely Australian Insects built a nest in the over-flow / float chamber breather on a Carb on one of my Minis. It ran bad and would stall about every mile, impossible to tune it too.

 

I thought I was going mad - took me over a week to find it!