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I have been having issues with my OER SK 40mm carbs. The problem is very elusive and I have not been able to find the source. I will do my best to describe the problem and I am willing to clarify if needed. I am going to refer to carb(#1) as cylinders 1 and 2. Carbs #1 and #3 are perfectly fine, it is carb #2 that is acting up. I started to sync the carbs, first by disconnecting all the linkages. I managed to balance #1 and #3 using an unisyn tool. However, #2 (cylinders 3 and 4) would be run leaner than the others. I unscrewed the idle mixture screws for #2 a few turns, and it leaned out even more resulting in popping out the carb and a nearly white spark plug. Also the #2 would draw a lot more vacuum than #1 and #3, and I unscrewed the idle speed screw for #2 and #2 still ended up drawing a lot more vacuum. #2 has enough vacuum that when I touch the unisync tool on #2 the engine will nearly die and then fuel spills out and then rpm picks up a lot. However, I got the car to idle smooth enough by tuning by ear and I would hold rpm at 2.5k and 3k and the #2 carb would cough and the exhaust would back fire, checking the plugs (cylinder 3,4) they were even whiter than at idle. Meanwhile the other plugs were a nice brown. This issue has bee driving me mad. Issues list: 1. carb #2 runs lean 2. (all linkages disconnected)(speed screw backed off 100% for #2) carb #2 still draws more vacuum that #1 and #3 3. Carb #2, touched unisycn tool the engine nearly dies, fuel drips out of throat, engine speed rises rapidly 4. #2 meaning cyl3,4 mixture screw(1 turn), nearly white plug, all others are a nice tan 5. #2 mixture screw(2 turns), completely white plug, all others are a nice tan 6. rpms held at 2.5k and 3k carb #2 cough and exhaust back fire 7. rpms held at 2.5k and 3k carb #2 (plugs 3,4) are bone white, all others are a nice brown 8. no binding in the linkages, linkages move very smoothly 9. Sprayed carb cleaner on all joints and seals, no increase in rpm 10. float levels all set to the same factory settings

Hello all from Australia, Long time browser, first time poster here because I finally can't find the information I'm looking for! First off, my name's Adam and I have a 1973 240z which is currently running a standard L28, N42 head/block combo, with brand new triple 45mm OER carburetors, and Trust headers to a twin 2" exhaust system. I have just installed a new set of OER carbs I purchased from Japan and am having difficulties sorting out the idle/low speed cruise setting. Bit of details into the setup, 45mm carbs 34mm venturis #190 air correctors (not yet tested to see if these are the best) #130 mains #60 idles #40 pump nozzle #1.8 needle valve 3.5psi fuel pressure from the mechanical fuel pump into Holley regulator 31mm fuel level using the OER level gauge. Idle screws are setup so that the first progression hole is just 100% covered looking through the brass cap/inspection hole. Carbs are balanced the best I can using a unisyn. I have a wide-band O2 sensor probe in the tail pipe. I am running 98 octane fuel. Timing is at 15 BTDC with no vacuum advance connected. Valve clearances have recently been adjusted. Now, onto the problem I am having.. Driving with the #60 idles installed, 1 full turn of the mixture screw turned out, slow acceleration and cruise is very rich, 10.5 and 11.5 AFRs respectively. I also have #50 idles on hand which I have installed to try and improve the current rich scenario and I cannot even get them to idle. With mixture screws out 1.5 full turns (recommended range is only 3/4 to 1 full turn), they cannot idle on their own, only when I blimp the throttle which I believe is activating the pump jets. With the #50s installed, AFRs are off the scale in the lean area. They can't idle let alone drive. My question is, is going down from a #60 to a #50 idle jet that big of a jump that the car can no longer idle on its own? Or is there something wrong with my idle screw setup? OER offer a #55, but I would like to double check with the experts out there first before spending that money. Any help would be appreciated. And please let me know if I am missing some information, I tried to be as detailed as possible. Thanks, Adam