Zenith Carb ****ing fuel.....

Longstride · Jun 11, 2018

Hi all, hope I'm posting in the right place!!!

My 1979 S3 petrol lightweight has recently started leaking fuel all over the hot manifold, and is also cutting out at idle, although runs fine with the foot down.

On inspection I can see the throttle spindle is very loose, I can literally wiggle it a good 3mm in either direction.

I'm supposed to be driving her over to France with the girlfriend this weekend too!

I've ordered a new bearmach zenith copy, but also a zenith refurb kit. Depending which arrives in post first, I'll fit one. Am I wasting my time with the refurb kit? Would the worn spindle be too far gone, i.e worn body too?

Any advice appreciated. Cheers.

jamesmartin · Jun 11, 2018

it will be the needle valve on the float ,worn spindle will weaken the mixture

Longstride · Jun 11, 2018

jamesmartin said:
it will be the needle valve on the float ,worn spindle will weaken the mixture

Thanks @jamesmartin so would that mean needle valve is worn and a refurb kit might sort me out?

jamesmartin · Jun 11, 2018

Longstride said:
Thanks @jamesmartin so would that mean needle valve is worn and a refurb kit might sort me out?

or float, could just be dirt,carbs worn loose spindle isnt helpful

brian47 · Jun 11, 2018

As @jamesmartin has suggested, the leaking is more than likely to be the needle valve at the top of the float chamber, either worn, sticking or dirt on the valve seat. Replacement is cheap and easy. It could also be a leak in the float causing it to float lower than designed. When you stick your foot down you're using more fuel, therefore not allowing the float chamber to fill completely.
It's unlikely that a refurb kit is going to do anything to repair the loose throttle spindle, especially if it's the carb body which has worn.

Longstride · Jun 11, 2018

Thanks guys. I'm glad I've gone for the two-solution pincer movent! I'll rebuild the zenith just for a laugh/experience and see how it works. I expect the bearmach copy will sort me out long term though. I'm hoping that's a reasonable compromise between a £40 cheapo job and an expensive Webber/SU full upgrade!

Bantam1 · Jun 11, 2018

Yeah, immediately thought float height and float valve.
Have had this problem many times on my old motorbikes.
Important to have correct valves too. Surprising how different ones can affect things badly.

Longstride · Jun 16, 2018

Update: in a race against time to her running before driving over to France I ordered two carbs. A £90 bearmach zenith copy and a £50 britpart one. They were exactly the same model from China! So the bearmach is going back!

Chucked the carb on, now runs sweet! I'm in France now, so far so good! Definitely a loss of power but much smoother running and very very quiet now. I'll check air filter when home as maybe it was getting some extra air via the old zenith throttle spinal where it was so worn!

Zenith Carb ****ing fuel.....

Longstride

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jamesmartin

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Longstride

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jamesmartin

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brian47

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Longstride

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Bantam1

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Longstride

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