Divisible_By_0 Posted October 20, 2016 Share Posted October 20, 2016 My 1980 BRAT idles at 1400 this seems really high to me and I can not get it to go down (was at 2k when I started but now lowered when giving it full throttle it goes the chokes for a second and goes real hard) by messing with the adjustment screws on the carb and i cant find anywhere that says or shows how to tune a carb (this is my firs carbed car I do not know anything) I am also wondering what the air/fuel ratio should be for this car. Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 20, 2016 Author Share Posted October 20, 2016 I have found the idle speed screw but I cant not find the idle mixture screw to save my life, my carb matched every picture I have seen of the stock hitachi carb for the 80 brat but they show the mixture screw next to the idle screw if I lower the idle anymore it dies and my air fuel ratio meter says it is as lean as the meter will read Link to comment Share on other sites More sharing options...
DaveT Posted October 21, 2016 Share Posted October 21, 2016 try finding a factory service manual, or someone who has a link to one. There should be a step by step procedure in there. 1400 is really high, if it's all warmed up. I've never had an 80 with a carb, so I can't be much more specific. Link to comment Share on other sites More sharing options...
naru Posted October 21, 2016 Share Posted October 21, 2016 (edited) Sounds like the idle stop solenoid is inoperative/unpowered or the idle circuit in the carb is otherwise blocked. Check for power at the solenoid.It should click w/applied power. If it is fubared,you can gut it to open the idle passage. Edited October 21, 2016 by naru Link to comment Share on other sites More sharing options...
naru Posted October 21, 2016 Share Posted October 21, 2016 http://www.autozone.com/repairguides/Subaru-ff-1-1300-1400-1600-1800-Brat-1970-1984-Repair-Guide/Carbureted-Fuel-System/Carburetor/_/P-0900c15280065ae8 Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 21, 2016 Author Share Posted October 21, 2016 http://www.autozone.com/repairguides/Subaru-ff-1-1300-1400-1600-1800-Brat-1970-1984-Repair-Guide/Carbureted-Fuel-System/Carburetor/_/P-0900c15280065ae8 I have read that my carb has two adjustable screws one controls where the throttle return stops the other is idle speed this is the carb on my EA71 engine that long slotted screw under the throttle arm is the Throttle return stop that flat head screw is idle speed these are the only screws i see on this carb that dont take it apart sorry its rotated I cant figure out how to fix it Link to comment Share on other sites More sharing options...
naru Posted October 21, 2016 Share Posted October 21, 2016 Long one is the throttle stop/idle speed screw. Bottom one is the idle mixture screw. It only adjusts idle mixture and will have no effect above about 1000 rpm as the carb will be running on the main circuit rather than the idle circuit. Check the solenoid. Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 21, 2016 Author Share Posted October 21, 2016 Long one is the throttle stop/idle speed screw. Bottom one is the idle mixture screw. It only adjusts idle mixture and will have no effect above about 1000 rpm as the carb will be running on the main circuit rather than the idle circuit. Check the solenoid. is the solenoid the part withe the wire coming out of it in the last photo? whenever I turn the screw you say is idle mixture it just changes the rpm Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 21, 2016 Author Share Posted October 21, 2016 As I am sure you have found this is my first carbed vehicle and I dont know what I am talking about, the idle is down to around 950rpm but the mixture screw is turned all the way in which would be it running extremely rich right? If I losen it any then the rpm goes to about 2k and it will not go any higher than that So I am assuming that I need to put the mixture screw back and move the choke to bring the idle down and all while it is doing this the engine is running on the choked side of the carb till I give it any amount of gas and it stays at that rpm but the other side of the carb starts using fuel Link to comment Share on other sites More sharing options...
naru Posted October 21, 2016 Share Posted October 21, 2016 Yes,that is the solenoid. It is normal for the rpm to change w/mixtiure changes. I`m surprised it has any effect at that rpm. Since the engine responds to idle mixture changes,that suggests the solenoid is OK,I`d check it anyway. I`d be checking to see if the secondary throttle is hung open. Recently had one w/high idle for that reason. Link to comment Share on other sites More sharing options...
naru Posted October 21, 2016 Share Posted October 21, 2016 As I am sure you have found this is my first carbed vehicle and I dont know what I am talking about, the idle is down to around 950rpm but the mixture screw is turned all the way in which would be it running extremely rich right? If I losen it any then the rpm goes to about 2k and it will not go any higher than that So I am assuming that I need to put the mixture screw back and move the choke to bring the idle down and all while it is doing this the engine is running on the choked side of the carb till I give it any amount of gas and it stays at that rpm but the other side of the carb starts using fuel Mixture screw all the way in means the idle circuit is getting NO fuel. A rough adjustment would be 2-3 turns out from bottomed. Don`t bottom it hard,they are delicate. Choke has to be wide open and the idle speed screw should not touch the fast idle cam w/adjusting idle speed and mixture. Do a rough adjustment on the mixture and then see if you can reduce rpm w/the speed screw. Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 22, 2016 Author Share Posted October 22, 2016 The solenoid works it shot the pin across my garage Link to comment Share on other sites More sharing options...
Divisible_By_0 Posted October 22, 2016 Author Share Posted October 22, 2016 (edited) Aww man thanks so much it runs so well now it doesnt sound bad or shake badly on start Edited October 22, 2016 by Divisible_By_0 Link to comment Share on other sites More sharing options...
skishop69 Posted October 22, 2016 Share Posted October 22, 2016 Idle solenoid? They don't have an idle solenoid. Some had an idle up vacuum pod if it had AC. That solenoid is the anti diesel or shut down solenoid. All it does is open on key on and close on key off to stop fuel in the idle circuit. Other than shutting off fuel, it has no effect or control of idle speed. Link to comment Share on other sites More sharing options...
naru Posted October 22, 2016 Share Posted October 22, 2016 Idle solenoid? They don't have an idle solenoid. Some had an idle up vacuum pod if it had AC. That solenoid is the anti diesel or shut down solenoid. All it does is open on key on and close on key off to stop fuel in the idle circuit. Other than shutting off fuel, it has no effect or control of idle speed. Also known as an idle stop solenoid. It will kill the idle if it does not work. Plenty of effect on the idle speed. Link to comment Share on other sites More sharing options...
naru Posted October 22, 2016 Share Posted October 22, 2016 Aww man thanks so much it runs so well now it doesnt sound bad or shake badly on start Cool! Link to comment Share on other sites More sharing options...
skishop69 Posted October 22, 2016 Share Posted October 22, 2016 Right. As I stated, other than shutting off the fuel... It can't cause the car to idle up. That was my point. Link to comment Share on other sites More sharing options...
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