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Setting the idle twin hS4E carbs


leon.halliwell
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My Spitfire idles far too low, about 550 to 600 rpm which causes the engine to die if i fully close the choke even when warm, there's a fairly complex explanation of how to set the carbs up in the Haynes manual but i was wondering if you can just adjust the idle screws without fettling with anything else because the car is running with just the right mixture and i don't want it to change.

 

regards

Leon

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If you turn both idle screws clockwise a quarter of a turn at a time until you are happy then don't worry, you shouldn't disturb anything else. Equally if you want to slow it back down a touch, turn both screws anticlockwise 1/4 of a turn at a time. The idle screws on mine are conveniently cross-marked. Give it a few revs between each adjustment and let it settle... patience required!

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For future twiddling, the balance is setting the idle air flow to be equal on each carb

You can use a proprietry tool quite cheap to measure the flow , you can diy a cover with tube and make a U tube manometer 

Filled with water  , or do what triumph did on supplies to the line ,  gas flowed settings were only developed when emmission controls took hold late in the 70s

Thats in simple terms a mechanical throttle setting, undo the idle screw so the throttle plates are fully closed, turn the screw in to just toich its cast stop, turn it in 1.5 turns    this will be as close to good as you can get when other means are unobtainium.

There is  some free slack travel on the interconnecting rod , the small levers on this rod need to be set to opertate the throttles equally

For this you undo the small clamp bolt and turn the lever on its shaft so both ends work together

This free travel is there so when using the choke the fast idle cam doesnt have to pull  the whole throttle linkages, the fast idle cam is also 

adjustable it has a small dome headed  tappet bolt there must be a gap between this and its cam when choke is in

If adjustment is needed the  fast idle on choke needs to be around 1500 rpm 

So realy no special tools required just a little observation and care 

Pete

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It will be when the suns up  dreaming of maytime for day 2

The last video I made is now on youtube look up RB44 production video  I had hair then but it doesnt get in shot

Myself Ray and Garth tried  to develope a how to video but the time required to cover all servicing aspect would have taken a liftime to 

complete and we dropped the idea

Pete

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Pete,

Perhaps we could film Twiddle day 2? An epic adventure staring Pete and Ray? 

A long long time ago in a galaxy far far away...............Pete Skywalker and his trusty crew battle against the dark side to save the Millennium Spitfire.

Could we get Ray into a Wookiee suit do you think?

Doug

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