pilot jet plug, needed? Symptoms?

[lightfall]

This is probably the stupidest thing I have ever asked, but, I am now realizing that pilot jet plugs may have been required on the BS34 carbs. Mine never had them when I did my teardown, and for whatever reason I thought reference to them from the carb guide was for the other carb models.

What would be the symptoms of a missing pilot jet plug? What is the function of this plug and what does it prevent from happening?

I have been tearing my hair out trying to figure out why my plugs look so rich even though I am pilot +1 and mains +2, and I have a raw pop on the left cylinder at idle and decel after checking compression, timing chain, valve clearances, exhaust fitment, swapping of coil wires side to side. Could this be the cause?

 

[I am Carbon]

I've never had them missing but I have had one go soft and leak.
But as it went bad that cylinder started popping, missing out, and finally quite running on that cylinder all together.
I while I was in there I replacing the plugs I also cleaned the carbs. anyway both cylinders run fine after

 

[lightfall]

Unbelievable! My right cylinder is fine, both plugs missing, but left pops like crazy and is a much harder start. Guess I will have to get some of these, I can see how sucking straight fuel from the bowl might be a bit much and would explain my sooty plugs despite modest jet increases.

Still doesn't explain the difference, I will have to reset everything all over again...

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[XSLeo]

I assume you have read the carb guide, so I won't suggest you read it. But just in case www.amckayltd.com/carbguide.pdf
Leo

 

[lightfall]

I've read it so many times it isn't funny. I did assume I didn't need the plugs as I do not think there was compelling evidence in the guide to suggest otherwise, though I've used it for everything else. Cleaned it out and jetted according to the guide 3-4 x now.

Seriously cursing the PO lately. Some sources cite the bs34 carbs having plugs and a channel between pilot and main and others do not. It threw me off I thought if they weren't there then I had a set that didn't need them...I don't know. I've read through the forums incessantly I don't have a good excuse.

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[lightfall]

Just as closure: when I got the replacement pilot passage plugs my sparkplugs stopped fouling. They were definitely necessary on my 81 with BS34 carbs.

 

[XSLeo]

From the research I've done the pilot jets draw air in through a jet in the carb bell, it mixes this air with a small amount of fuel through the main jet, then sends this mixture through passages to the idle mix screw and holes by the throttle plate. The mix screw adjusts the mix at idle and controls about 25 % of the mix.
With out the plugs the jet just draws raw fuel straight from the float bowl. No air gets mixed in. This might work with a very much smaller pilot, but I doubt it.
Leo