SQ4 4G carb problems

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john.davies
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SQ4 4G carb problems

Post by john.davies »

Having now resolved the non starting when hot problem I was having recently by fitting a Thorspark electronic ignition system to the mag I would now like to fix the annoying issue of the bike hesitating for a moment when travelling along at a fairly closed throttle and then you accelerate. It's like a cough then off she goes. I have tried float height and adjusting the mixture screw underneath on the Solex but it still happens. The carb was reconditioned by David Jones just before he packed in so should be in good condition and correctly set up. It has always done this since i first got her back on the road. Does anybody have a suggestion on what else to try.
Image 1931 Ariel VB31, 1935 Triumph 5/3 project, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10 Super Flash, 1954 Ariel VH
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chris.shearwood
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Re: SQ4 4G carb problems

Post by chris.shearwood »

John,
Do you have a copy of the Instruction Booklet - Self-Starting Solex Carburettors? It explains some of the theory of operation of these carbs and might lead you in the right direction to solve the problem. Let me know If you don't have the booklet so I can scan some of the relevant documentation for you.
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Pete.Silson
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Re: SQ4 4G carb problems

Post by Pete.Silson »

John,

I had a similar issue - I found that crud had got into the air correction jet and blowing this out with an airline cured the problem. This jet does seem rather prone to collecting detritus being open to atmosphere at the top of the carb.
Air Correction Jet.jpg
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john.davies
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Re: SQ4 4G carb problems

Post by john.davies »

Thank you for your responses, I have just downloaded Instruction Booklet for Self-Starting Solex Carburettors and reading it does sound like the correction jet may be the problem as the cough happens when you first open the throttle after a steady slow run, say through a 30mph area, and then she accelerates well. The carb has only done 300 miles or so since David Jones reconditioned it and it has done this from day 1. Could it be to do with jet sizes? I'm sure she is standard setup with 23 choke tube, 120 main jet, 70 aux jet and 150 air correction jet
Image 1931 Ariel VB31, 1935 Triumph 5/3 project, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10 Super Flash, 1954 Ariel VH
Pete.Silson
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Re: SQ4 4G carb problems

Post by Pete.Silson »

The carb has only done 300 miles or so since David Jones reconditioned it and it has done this from day 1.
John,

It would still be worth a quick check of the air correction jet. It can be quickly removed and checked without disturbing anything else on the bike.

This jet seems to be the perfect shape and position for foreign objects to drop into and could easily have picked up a fleck of something during assembly of the bike.

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john.davies
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Re: SQ4 4G carb problems

Post by john.davies »

Hi Pete, I've taken the air correction jet out and given it a good blow through. Can't take her out until tomorrow to find out if she's sorted. I'll let you know. Cheers John
Image 1931 Ariel VB31, 1935 Triumph 5/3 project, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10 Super Flash, 1954 Ariel VH
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