Carb jet size for a 30mm carb

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James Baxter
Posts: 154
Joined: Mon Jun 12, 2006 2:13 pm

Carb jet size for a 30mm carb

Post by James Baxter »

We are bolting a Zenith 30mm carb on the 1928 Sports Jowett. HZ carb.
we have such a wide choice of jets to choose from, but no idea where to start.
We are thinking 87.5 jet for the main. 90 for the compensating jet.
Has anyone got any thoughts or experience?

thankyou,
James
Restoring a 1924 Short 2
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k. rogers
Posts: 480
Joined: Thu Feb 23, 2006 9:43 pm
Your interest in the forum: 1933 7hp Kingfisher
1935 7hp Weasel
1928 7hp Sports replica
1952 Bradford special
Given Name: Ken
Location: Cornwall

Re: Carb jet size for a 30mm carb

Post by k. rogers »

Sounds about right but in my experience it seems that it varied slightly from engine to engine. The proof of the pudding will be in the eating! Don't forget, even the throttle tubes were available in various sizes too!
7hp Weasel & Kingfisher
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Brucegirvan
Posts: 91
Joined: Sun Mar 12, 2017 5:59 pm
Your interest in the forum: Interested in pre war Jowett cars.
Jowett ED 6036 June-1930. Originally a long 2 tourer, converted later to fabric bodied light four.
Jowett PO5051 1929. Originally light 2. Converted to Sports style In 90’s.
Member of VSCC and LCEOS for marshalling and tours. My son (Matt) is now interested in autosolos and trials - ideal Jowett territory. He now owns VO4165, 1930 Long 2 as an oily rag road car.
Given Name: Bruce
Location: Haywards Heath, West Sussex

Re: Carb jet size for a 30mm carb

Post by Brucegirvan »

James - hope you’re having fun. Do you have a copy of the Pre War Technical Manual? It gives some guidance
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James Baxter
Posts: 154
Joined: Mon Jun 12, 2006 2:13 pm

Re: Carb jet size for a 30mm carb

Post by James Baxter »

Very interesting - thankyou Bruce.
Twin carburettors? I wasnt sure any had twin carbs, but it makes perfect sense . The sports was surely twin. ? Who knows?
Restoring a 1924 Short 2
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k. rogers
Posts: 480
Joined: Thu Feb 23, 2006 9:43 pm
Your interest in the forum: 1933 7hp Kingfisher
1935 7hp Weasel
1928 7hp Sports replica
1952 Bradford special
Given Name: Ken
Location: Cornwall

Re: Carb jet size for a 30mm carb

Post by k. rogers »

The Weasel was available with twin carbs, but I gather they were a bit of a pain to tune as there was no balance pipe, so most people changed them to the normal single carb.
7hp Weasel & Kingfisher
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James Baxter
Posts: 154
Joined: Mon Jun 12, 2006 2:13 pm

Re: Carb jet size for a 30mm carb

Post by James Baxter »

What size and type were the carbs when fitted as a pair please?
Restoring a 1924 Short 2
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k. rogers
Posts: 480
Joined: Thu Feb 23, 2006 9:43 pm
Your interest in the forum: 1933 7hp Kingfisher
1935 7hp Weasel
1928 7hp Sports replica
1952 Bradford special
Given Name: Ken
Location: Cornwall

Re: Carb jet size for a 30mm carb

Post by k. rogers »

On the Weasel they were still the same size Zeniths as on the other Jowetts at that time, ie 30mm, but adapted to take the dual control rods.
7hp Weasel & Kingfisher
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