Date registered: Feb 2005
Vehicle: 1989 W201.029/M103 3.0
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
RE: 114 Carbs.
Okay, so it's a twin carb (that'll teach me for having my head buried in M110's and then disappearing for a while).
Just looked up some plans for those carbs (zenith
Problems could be:
first port of call, check all seals and gaskets for vacuum leaks (high neutral idle/low in gear suggests lean rather than rich mixture, the fact your plugs aren't blistered down the centre or clearly light grey suggests it's not mixture settings that have graduallyl gone out of tune but possibly a vacuum leak).
next, carb balancing. I had a big set of triple sidedraught carbs on my own engine and in some cases would have to rebalance the carbs a few times in one weekend of driving to get my 250-odd hp.
zero the linkages between the carbs and turn up the idlers equivalent turns, make sure there's a return spring fitted to each throttle valve to keep each butterfly hard against the stops (technically one throttle return spring must be fitted to each seperate throttle butterfly on an engine for roadworthy but this may be regional, I retrofitted three springs for three carbs from the original one for the whole set on mine...it was an old setup off a 70's stock racer). Balance the mixture primarily using periodic examination of plugs from front to back after zero'ing a starting point with a vacuum guage. My rear carb always ran richer than the middle one, the front carb leaner, so I adjusted for it manually to get them balanced dynamically.
apparently those zeniths have a problem with secondary valves sticking. use good doses of carb cleaner.
the throttle butterfly adjuster (a heat variable adjustment run by vacuum), sometimes has problems which would lead directly to idling problems all over the place. The heat sensing valve sometimes need to be tossed.
the mixture recirculating system sometimes fails or just plain falls off.
they're prone to general clogging, some suggest running cheap carb cleaner additive in every tank of gas with old ones.
Man I would toss those zeniths so fast you wouldn't even hear them hit the bottom of the bin before a set of sidedraughts somethings, downdraught webers or just a decent little four-barrel was being bolted on.
driving a fast car should feel like falling off a building.