Carbuerator Mixture Adjustment ?
Moderators: notoptoy, S Allen, Solex68
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Illinois Roadster Owner
Carbuerator Mixture Adjustment ?
Hi ! I in need of some expert advise on adjusting the fuel mixture on the twin sidedraft carbuerators on my 1969 SPL 311 1600 Roadster ! I believe my car is running too rich because I'm getting black smoke from the exhaust ! Any help is much appreciated !! THANKS DON !!!
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TR
This could be a 100 page answer...
Assuming everything is in proper working condition and after making sure that absolutely everything else is properly tuned;
Points
Timing (Vacuum & Mechanical Advance)
New Spark Plugs
New Air Filter
Vacuum Lines
Overflow Lines
Float Levels
Clean Carb Piston Oil (light enough for winter)
Carb. Airflow Balance
Etc., etc., etc...
If the carbs are old, replace the needles and seats before starting this process. Once they wear, it is very hard to get an accurate mix.
Assuming these are SU's...A good starting point is one and a half turns from bottomed out. Tighten the mixture nuts (tighten=upward) till they bottom out. It is a good idea to ensure the carb piston can move freely every turn or so. When the nut is at the very top, back it off one and a half turns. There are dots or flat spots or some indicator on the nut to help you count the turns. I like to use a red fine point sharpie to mark the nut as it is very easy to see. I usually put one mark at bottomed out and a pair of marks at one half turn from there. It makes it really easy to count turns.
Now the hard part - Drive, drive, drive! If you notice any pinging, lower the nuts a full turn. Check the spark plugs after at least 20 miles, you want a milk chocolate colored (Hersey bar in full sunlight) plug. Try not to run the engine on the choke during this evaluation period-use it only to get the engine started, then try to keep the engine at 2000 RPM till it is warm enough to drive.
If it is too rich (dark sooty plug), lean the mixture by tightening the nuts. If it is too lean (white plug), richen the mixture by loosening the nuts.
Don't be disapointed if you do not get the mixture right the first time, it usually takes a few tries and a few sets of plugs. Good Luck!
Assuming everything is in proper working condition and after making sure that absolutely everything else is properly tuned;
Points
Timing (Vacuum & Mechanical Advance)
New Spark Plugs
New Air Filter
Vacuum Lines
Overflow Lines
Float Levels
Clean Carb Piston Oil (light enough for winter)
Carb. Airflow Balance
Etc., etc., etc...
If the carbs are old, replace the needles and seats before starting this process. Once they wear, it is very hard to get an accurate mix.
Assuming these are SU's...A good starting point is one and a half turns from bottomed out. Tighten the mixture nuts (tighten=upward) till they bottom out. It is a good idea to ensure the carb piston can move freely every turn or so. When the nut is at the very top, back it off one and a half turns. There are dots or flat spots or some indicator on the nut to help you count the turns. I like to use a red fine point sharpie to mark the nut as it is very easy to see. I usually put one mark at bottomed out and a pair of marks at one half turn from there. It makes it really easy to count turns.
Now the hard part - Drive, drive, drive! If you notice any pinging, lower the nuts a full turn. Check the spark plugs after at least 20 miles, you want a milk chocolate colored (Hersey bar in full sunlight) plug. Try not to run the engine on the choke during this evaluation period-use it only to get the engine started, then try to keep the engine at 2000 RPM till it is warm enough to drive.
If it is too rich (dark sooty plug), lean the mixture by tightening the nuts. If it is too lean (white plug), richen the mixture by loosening the nuts.
Don't be disapointed if you do not get the mixture right the first time, it usually takes a few tries and a few sets of plugs. Good Luck!
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LongBeach311
I just synchronized my carb for my 1968 1600. What I did was
1. Well, timing was at 0 degree, make sure you have ATF oil in the bell. disconnect the vacuum hose from dist to carb, and plug the one on the carb.
2. disconnect the throttle links that connect to the main linkage
3. undo the idle screw and change the springs, turn them clockwise until the link started to move, add another 3/4 a turn.
4. do the same for the other carb, and start the engine.
5. listen to the hiss from each carb using a 1" diameter hose, make sure they sound about the same 600-800rpm.
6. underneath (left) of the vacuum chamber there is a needle sticking out, that is the piston lifter. On the rear carb, lift the lifter a little bit and if the car died, you need to higher the jet by turning another knob right underneath the bell, if the car is totally fine that means you are too rich, then turn counter clockwise. You want the car still running as if on 2 cylinder, kinda rough but steady.
7. Do the same to the other carb
8. plug the vacuum hose back
9. if the rpm rises then, adjust it again to 600-800 rpm
10. connect the linkages to the main one
1. Well, timing was at 0 degree, make sure you have ATF oil in the bell. disconnect the vacuum hose from dist to carb, and plug the one on the carb.
2. disconnect the throttle links that connect to the main linkage
3. undo the idle screw and change the springs, turn them clockwise until the link started to move, add another 3/4 a turn.
4. do the same for the other carb, and start the engine.
5. listen to the hiss from each carb using a 1" diameter hose, make sure they sound about the same 600-800rpm.
6. underneath (left) of the vacuum chamber there is a needle sticking out, that is the piston lifter. On the rear carb, lift the lifter a little bit and if the car died, you need to higher the jet by turning another knob right underneath the bell, if the car is totally fine that means you are too rich, then turn counter clockwise. You want the car still running as if on 2 cylinder, kinda rough but steady.
7. Do the same to the other carb
8. plug the vacuum hose back
9. if the rpm rises then, adjust it again to 600-800 rpm
10. connect the linkages to the main one