I'm putting up this page of overhaul info in the hope that it may be of some use to someone getting their hands dirty for the first time with the Dell'Orto pumper carbs, as well as a reference for myself when I inevitably have to do all this again. NOTE: this is a work in progress & a bunch of words and reference tables are not yet in place. I'm going as fast as I can...
When I bought my LeMans III the mixture was just unbelievably rich. Adjusting the choke cables so they would go slack when released reduced the incidence of flooding to only a daily annoyance. Going to one grade hotter plugs meant I could get as much as 20km out of a set of plugs before they joined the others in the "fouled plugs" container. Trying to adjust the idle mixture has shown that the sinister (left) idle circuit wasn't working at all - the adjusting screw was wound in about as far/rich as it could get - and pulling off the dexter (right) plug lead still gave an instant stop at any and all settings of the idle screw. The only reason it idled at all was because the dexter side is so damned *rich* - once off idle it ran on two quite nicely, right up until it fouled another plug...
It's obvious the carbs needed an overhaul and quite likely rejetting in the process.
I discovered the process of finding out "what to do" is surprisingly difficult, given the vast amounts of literature out there on carburettors and Dell'Ortos in particular. I have overhauled dozens of the CV style carbs on Jap bikes (all of which have minimal adjustability) and have maybe six different manuals on carburettor theory and overhaul, none of which in any way helped with this particular pair of carbies. The Dell'Orto and Guzzi factory manuals are particularly unhelpful in this regard. And even Google was not much help - most of the stuff published on people's websites are reprints of what I already have.
As soon as I managed to get on the AIGOR mailing list (thanks Peter), I put out some feelers and Pete Roper was good enough to share some tips with me (thanks Pete). In summary:
Make sure the choke plungers actually seat when closed and the rubber pads haven't dropped out of the plungers
Make sure the previous owner hasn't jetted the carbs like older Guzzis, as they needed much bigger jets than the LeMans III's "lean burn" carbies do.
Check mains, idle circuit, slide cutaway and atomiser with the above over-jetting in mind.
To which I will also add "check the float level"
Follow the links below to see the stripping process from go to whoa in glorious "digicolour"
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