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Carb question(solex)


scatman75
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Is your timing set correctly? 

 

Is the choke butterfly completely open?

 

Which adjustments are you trying?  Idle SPEED screw should be barely engaged, then set the idle MIXTURE screw to highest/smoothest idle...then the idle speed screw can be used to bring idle to about 950-1000rpms.

 

Is the throttle rod adjusted so when it is relaxed, it is not opening the throttle butterfly slightly?

 

Pics, sometimes helps diagnose... It's probably something simple.

 

Ed

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Take out the idle jet and clean it.  It's a small orifice, look closely up to a light.  That's the usual idle problem.  Adjust idle mixture after cleaning the jet, it's located behind pc 15 (or where a pc 15 woud be if you don't have a pc 15)

Edited by jimk
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Baseline for many carbs. It's easy. 

 

Engine should be at operating temperature and choke plates wide open. 

 

Lightly seat the mixture screw then back it out 1 1/2 turns. 

 

Idle speed screw should barely touch the arm of the throttle butterfly lever, then about 1/2 -1 turn more. 

 

Start engine. Will it idle on its own without having to give it some foot-feed? If not, begin backing out the MIX screw about 1/2 turn at a time. Any change in rpm? You are looking for the spot where it idles smoothest. You may need to turn the speed screw just a bit... but not too much. 

 

Typically, a Solex should idle at 1.5-2.5 turns out from lightly seated on the mixture screw and the speed screw 1/2-1 turn in. 

 

Try that. 

 

Ed

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Note items 8 and 10 on the above diagram. Both are likely to effect the idle speed and both will have a mysterious baseline setting since the manual helpfully just says 'don't adjust'!

 

I had a look through my incomplete electronic version of the shop manual but the detail is likely missing. There are a number of values given in the tabular details at the front of the section for throttle plate being open (in mm) that I don't really understand. This may be a baseline throttle setting with the rest of the idle adjustment done by the air bypass. Perhaps if you can get a full copy of the fuel system section of the manual it may give better context. 

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Also check the ratchet mechanism (fast idle cam) that boosts the idle speed when the choke is open.  I've seen those Solexes where either the linkage or the ratchet teeth on the fast idle cam are worn, allowing the idle speed to stay up even after the choke closes all the way.  That's the main reason I gave up on that Solex back around 1980 or so and bought a manual choke Weber...

 

mike

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