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Discussion Starter #1
Bon jour All,
With about 1500 miles running in new engine have noticed with 98 Premium fuel that 2HL plugs loaded with soot. Idles quite smooth when cold and even at 6 degrees C or 40F never had to use choke. When Hot the idle becomes lumpy and you get bounced a bit in your seat waiting at traffic lights. I have a basic Autobook description of the DHLA 40 G and with luck the design is the same as my DHLA L's. I have found a good Weber service manual but yet to find one for Dellorto's.
The cam's are 105 48 Euro on the 1983 Alfetta 2 L and I would like to try adjusting the four mixture adjusting screws but first would like to find out if screwing in will lean out mixture or make it rich.
Any thoughts or guidance would be appreciated.
Regards Geloso.
 

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Before tuning you should ensure that they are synchronised properly - this can easily be done by undoing the progression hole plugs and shining a light down the throat of the carbs and lining up the butterfly valves. After you are sure they are balanced, you can tune it.. turning the mixture screw in will lean it out. Do each screw individually - the engine revs should rise as the mixture leans out, you should get to a point where a quarter turn in each direction will cause a drop in revs, then move on to the next one. If the revs rise too much take it down via the idle speed adjustment screw. It's important the revs don't rise too much otherwise it will throw off the adjustments - try and keep it at about 900.
 

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Discussion Starter #3
Hi JoshV12345,
Thank you very much for the quick reply and sharing your knowledge on the DHLA'S. Your advice re the Progressive hole plugs will be carried out and I expected that screwing in the mixture screws would lean out the idle mixture. I have tried using a feeler guage on a spare set of DHLA40 G to check butterflys valves to give me some idea on synchronisation.
I have a set of four vacuum gauges that I will try out when adjusting the mixture screws.
I thought I would wait till the new engine had about 4000 miles on the clock before I check the compression figures, but so far so good.
After I adjust the Carbs Josh I'll take a good run on the open roads and then check the plugs to get a reading on the main jets, before letting the car idle.
Once again thank you very much for you interest, it was appreciated.
Regards Geloso.
 

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Like Josh said, remove the progression hole plugs and advance the throttle until you can see the butterfly plates cover the first hole it comes to. Compare the other carburetor to that and see if it needs to be advanced or retarded to bring it in closer to synchronization. From there that should get you close to having to turn the synch screw a half turn either way to achieve a nice balance. I set the idle mixtures first and balance last.
 
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