Speedmaster Master Catalog by Studio Eighty. Six. Speedmaster Master Catalog   Published on Nov 2. From Radiator to Rear End. How to tune SU Carburetors. Tuning your SU carburettors by Scott Fisher. Ive been meaning to write this up for some time, ever since I did the SU Performance Tuning 1. This one is more like Basic SU Adjustment for Happy Driving. The trick to tuning SU carbs is to understand that there are two things you need to get right the air flow, and the fuel mixture. While they are interconnected, they are also independent, and need to be measured and adjusted independently. Special Tools. You will probably need to arrange to buy or borrow a Unisyn flow meter. The Unisyn is the usual gauge for getting the air flow balanced between the two carbs. This costs about 2. It consists of an adjustable opening same size circumference, but with a disc on a threaded rod that you can screw tighter or looser that you use to set the level of a little float that rises or falls in a glass tube at the side of the gauge. For the fuel mixture, I have become sold on a device called the Gunson Color. Tune maybe Colour. Tune, as its a British co. This is a spark plug with a crystal pressure and heat resistant window in it that lets you see into the combustion chamber while the motor is running. The color of the flame indicates the mixture richness. It costs about 4. SU-Carb-Cleanup.jpg' alt='Su Carburetor Balancing Tool' title='Su Carburetor Balancing Tool' />If you dont have a Gunson, Ive included the standard directions here for determining correct mixture step 4 of the Adjusting Mixture procedure. To tune SU carbs, first locate the following components Throttle linkage nuts. These are the things that connect the throttle linkage the bar connected to your foot through whatever means your car uses, cables or rods to the carburetors throttle levers. Throttle stop screws. These set the idle speed for each carb, and are located typically behind the dashpot, on the same side of the carb to which the throttle linkage connects. Mixture adjusting nut. This is the lower of the two nuts at the very bottom of the carburetor. Su Carburetor Balancing Tool' title='Su Carburetor Balancing Tool' />Later SU carburetors of the HIF type have integral float chambers, on which the mixture is adjusted by turning a screw. Youll need to experiment and I explain how to see which way makes this richer and which way makes it leaner. Lifting pins. These are little wobbly metal pins under the dashpot. Idm Patch Version more. When you push up on the pin, it raises the piston in the dashpot. Find these theyre crucial if you dont have a Colortune. If you dont have or cant find them, you can raise the piston with a flat bladed screwdriver pushed down the throat of the carb and twisted to lift it. Manual Do Aluno Unicamp 2012 on this page. The bridge. This is the part inside the carburetor, where the gas jet opens into the airstream. Youll see a needle inside the jet, and the jet itself should be a few fractions of an inch down from the bridge itself. The jet is the brass tube that sits in the center of the bridge, with a tapered needle poking down into it. The choke linkage nuts. Comparable to the throttle linkage nuts and usually the same size, but on the linkage that goes between the choke cable and the mixture adjustment mechanism. They make sure that both carbs are enriched when you pull on the choke. Balancing The Air Flow. Start with the engine warmed up to operating temperature and perform your standard ignition tune up points gap, timing, spark plug gap, new condenser, etc. Certain questions come up all the time on the various discussion boards, particularly theSambas popular Baywindow Forum. This is a FAQ made up from my replies to. In general, the Moss Motors Video site and MG Guru Site have excellent technical articles. First, go to Michael Salters Blog at. CARBURETORS and EXHAUST TECH. CB101 CARBURETORS You May Find on the MGA. CB102 CHOKE ADJUSTMENT and fast idle CB103 COLD WEATHER STARTING. By Dan Mooney The longest running blog in the automotive world. K and G Cycles has all the hard to find motorcycle parts and accessories at the best prices online. From vtwin to metric motorcycles, youll find everything from. If youve got a timing light and a dwell meter, you can verify all that stuff independent of the way the car is running. When its warm, shut the motor off and remove the air filters. Begin by balancing the air flow. Su Carburetor Balancing Tool' title='Su Carburetor Balancing Tool' />To do this, first loosen the throttle linkage nuts. Leave them connected, just loosen them half a turn or so. Back out the throttle stop screws till you can see that they are just touching the throttle stop. Then open each carburetor that is, lower the throttle stop screw 1 12 turns of the throttle stop screw and start the engine. Su Carburetor Balancing Tool' title='Su Carburetor Balancing Tool' />It will probably idle at about 2. RPM dont worry. Put the Unisyn over either carb and adjust the orifice in the Unisyn till the little float at the side rests at the middle of its graduated tube. Su Carburetor Balancing Tool' title='Su Carburetor Balancing Tool' />Pre diagnostics if the idle drops and the car wants to die when you slap on the Unisyn, the carb is too rich if the idle soars upwards, its too lean. Hold the Unisyn over the carb for only long enough to see the level of the float, then remove it. Place the Unisyn on each carburetor in turn to check its flow, adjusting the throttle stop screws until both carburetors register the same position on the graduated tube of the Unisyn. The float will probably move either up or down in the tube, which is why you want to center it in Step 4. When both carburetors flow the same amount of air, tighten the throttle linkage nuts, adjusting for the amount of free play between the linkage and the throttle stops that your manual calls for probably about 0. Your goal should be to achieve the lowest possible idle with both carbs balanced and the engine running smoothly. Note that the idle speed will very probably rise as you get the mixture correct. If youve taken more than five minutes to do this, rev the engine to over 2. RPM assuming the idle isnt already that high for thirty seconds or so to clear the spark plugs. Then adjust the mixture. Adjusting The Mixture Note in the following procedure, one flat is the basic increment of adjustment, and refers to 16 of a turn of the mixture adjusting nut. This corresponds to the flat faces on the nut. Im going to give instructions for SUs with the separate float chambers. If you have the HIF integral float carbs, youll have to look in a manual to see whether you turn the mixture screw to the right or the left to make it richer or leaner Ive done that once but I cant remember. Alternatively, you can with the motor shut off peer down the throat of the carb and turn the mixture screw while watching the top of the jet. Remember that moving the top of the jet up will lean out that carb, while moving the top of the jet down will richen it. Buy Deluxe Carburetor Airflow Meter Air Flow Meters Amazon. FREE DELIVERY possible on eligible purchases. Find www. DellortoShop. FaceBook Bringing you mre than 3. DellortoShop. com, RicambiCarburatori. CarburettorShop. com are. Oldsmobile FAQ Carburetors section. Nomenclature. For a squarebore carb, the primaries are significantly smaller and typically do not share the same centerline as. Shut the car off and loosen the choke linkage nuts. Adjust the mixture nuts screws fully lean. For separate float chamber cars, this means raising the mixture nut all the way up against the bottom of the carb or rather, against the spring. For HIF carbs, you can try turning the screw while looking down the throat to see which way the jet is moving. In either case, the idea is to zero out the jet raise it all the way up in the bridge. Now drop the jet an equal amount two full turns for HS type carbs, two full turns I believe for HIFs. Then start the car. Note In the following step, you might want to consider adjusting the carburetors one half a flat too lean, as the mixture will be enriched when you put the air filters which restrict air flow on at the end of the tuning process. Raise the lifting pin or use a screwdriver if you dont have the pins so that the piston rises no more than 11. Listen to the engines exhaust note and compare it to the following conditions If the exhaust note rises and stays high till you drop the piston, this carburetor is adjusted too rich. Turn the mixture nut one flat one sixth of a turn up, moving the jet toward the bridge, then repeat Step 4. If the exhaust note falls and the car sounds as though it is going to stall, this carburetor is adjusted too lean. Turn the mixture nut one flat one sixth of a turn down, moving the jet away from the bridge, then repeat Step 4. If the exhaust note rises briefly and then settles back down to something like the original RPM level, this carburetor is set correctly.