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Discussion Starter #1
I'm trying to wake up my Alfa spider '84 (equiped with 2 solex carbs) and have some issues with the engine. It runs poorly and I have done some maintenace (changed the rubber mounts, vac.tubes etc) but it still runs badly. I have no respose when adjusting the idle mixture screws (regardless how much I turn, except when reaching the bottom). Only time I see some difference is when advancing/retarding the timing but then the engine will not start. Any ideas?
 

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Start with basics. How is the compression when hot, and are all 4 plugs firing? What do they look like, as in black, white or oily? Then move to timing and fuel issues. You probably should try to get back to a baseline close to before you messed with screws, and a manual will help with that. Maybe start with a turn and a half out if it has been really mucked with.

Need compression, fuel and timed spark, so that narrows it down somewhat.
 

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listening to the video I would say carburation, its eager to run on the electrical side but are you sure you have the plug leads correct?
 

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Discussion Starter #4
hello,

-Compression already checked and it's very good.

-Plugs are black and I can see some oil as well. They are firing (if I remove the cable from one plug at time I can hear the the engine rpm goes down a bit, but maybe there is a better way to check?).

-The screws on the carb are in the original position but nothing happens if I turn them up/down which maybe shows that the carb is not the issue.

-The cables seems to be connected i right order - when checking TDC of cyl no 1 the rotor is pointing at the radiator/fan which should be correct according the collective knowledge on this forum :)

Also checking the timing is little difficult sice I suspect that the rpm counter is not showing true rpm so I'm not sure where 5000rpm are as mentioned in the manual.
 

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ignore the tacho. Firing order 1342 i seem to recall, if plugs are black it says the carbs are not right. how does the exhaust smell when running? black soot at tailpipe i bet.
 

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Choke stuck?
 

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Discussion Starter #7
well, difficult to describe the smell but I would say it smells like burned gasoline :) Noticed one thing this evening, when I disconnect the cyl no 1 cable no change in the "sound". If I remove 2,3 or 4 then I hear clear "drop". This puts everything in another direction, maybe the cyl no 1 wasn't working all this time. I have spark all the way and I've also tested to alter the plugs but the problem still remains at cyl 1. As the compression is good, I'm not really sure what to look for.
 

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A severly fouled plug (#1) will spark without doing much of a job igniting the cylinder and a stuck choke on the carb feeding that cylinder may be fouling it. Something to look at. Sounds like you're on the right track.
 

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don't know how old your carbs are but if the shafts are worn adjusting the idle screws is an excerise is futility. Float level is also something to be looked at. no air leaks? which is basically what a worn throttle shaft is.
 

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Discussion Starter #11
checked compression again, looks good on all cylinders. Cold engine gives 170psi on all 4 and warm engine gives 180-185psi on all. How do I check if the fuel supply to the cylinders is ok?
Noticed also that the engine is backfiring on cyl no3.
 

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The reason for synchronizing the carbs is so that the front carb and the rear carb both flow the same amount of air. If the carbs are not synchronized, no amount of mixture adjusting will cure a rough idle.
If no one else posts the procedure, I will look to see if I have the Alfa procedure.
I can not tell from the video if the airbox is installed or not. It MUST be installed in order to prevent each carb from moving independent of the other and is required, along with the airbox support rod, in order to synchronize the carbs.

BTW, it sounds like the valve clearances/cam timing should be checked.
 

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Discussion Starter #15
the air box is not installed (I needed the space when I was changing the engine mounts) but I will re-install it asap. I have Solex carbs, but the sync procedure is maybe similar to other carb types.....
 

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I have sent you a private message.
 

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Discussion Starter #18 (Edited)
ok, some update - after adjusting the throttle position the engine runs much better, the vibrations are almost gone (thanks papajam) but it looks like it runs extremely lean. I had to turn the idle mixture screws almost all the way out in order to have the engine run without stalling. I took the car out for a drive this evening and the engine responds very quickly but the smell of the exhausts is somehow strange, smells to much gasoline...
Anyway, I consider this as progress :)
 
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