912 Registry :: Air Fuel Mixture

From: PAUBOOKER; I have got a set of Dellortos with a Bosch 205 and I balance with the flowmeter, ensure that both linkages open at the same rate, adjust the idle mixture screws about a half turn rich of fastest idle, and didled the main jets until I eliminated any power holes in acceleration. I have a reamed pair of mains now, Dellortos offerings were a little too lean or a little too rich so I split the difference. From the look of the plugs it is running rich but well. Paul

From: Jones Low; I've been experimenting with the Gunson Gastester with mixed results. The Gastester measures CO% and so far it does seem to do a good job of measuring CO level. I'm currently measuring about 4.5-5.0% CO, carbs are in synch, and the idle at 850-900 rpm. The engine exhaust is leaner (using my "nose" measurements). But the engine has a little more popping through the carbs than when it was running richer (7.0% CO). I
going to continue to fiddle with the idle mixture screws and see if I can dial it in. It nice to see the readouts and see the numbers changing as adjustment are made. Anyone else using a gas analyzier and what CO% readings are you getting?
Jones Low, 69-912

From: Carlos Musquez; Like Joshua Harrison suggested I do the same. Turning the idle screws on each in until it is dead then turn out 1/2 turns. You will be surprised at how easy it is to hear the car run well. Nothing beats the senses, site, sound and smell.
I have a related question. What size jets are you using? And do you swap
jets in the winter/summer?
I have webers...........thanks, Carlos

From: Larry; On my 912 I have it running excellent using a flow meter..............LARRY

From: Joshua Harrison; To tune Weber 40 IDF's I turn the idle mixture screws in until the rpm's drop and the cylinder is dead. Then turn it out 1/2 of a turn. If the car runs rich, turn the screws in a 1/4 of a turn, if it's running lean turn them out a 1/4 of a turn. The screws should be about 1.5 to 2 turns out. If not you need to change, or ream out, the idle jets. Solexes should be about the same way. Haynes as well as may other companies make good carburetor manuals. However, the best, and cheapest, analyzer or tool to adjust your carbs is your ear. After almost 2 years I'm finally getting good at it. It just takes time and practice.

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