Guest Anonymous Posted February 25, 2002 Share Posted February 25, 2002 I have a 1971 240Z I just picked up all original stock. I was messin with the adjustments underneath the carbs and now I cant get it to work right. When its cold it will run good then when you rev up engine and it warms up it just starts to die like its not getting any fuel or like its running on one cylinder. I turned dials clockwise from top all the way in then 3 turns back out on both sides and now it wont run right..I was trying to tune it richer or leaner but now I cant do anything with it. any help appreciated. ShredZ Quote Link to comment Share on other sites More sharing options...
Miles Posted February 25, 2002 Share Posted February 25, 2002 Looking from the bottom of the carb turning the wheel clockwise will richen the mixture. I turned mine all the way in full rich until the adjusting knob stopped and then backed it out in full turn increments. Mine seems to run best at 2.5 turns out from full rich. Check for air leaks in hoses and gaskets. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 25, 2002 Share Posted February 25, 2002 Do you have to mess with any other settings like timing. It was running perfect till I messed with those mixture settings.. I meant to say looking from top I turned both carbs counterclockwise all the way then 3 full turns out for lean but now it just dies as soon as it heats up. Starts fine cold then it just totally dies and have to let it sit a little bit before trying anything. Quote Link to comment Share on other sites More sharing options...
DAW Posted February 26, 2002 Share Posted February 26, 2002 Do a search of this site for SU adjustment tips. I know I responded several months ago to a similar post. First of all, don't do anything else (timing, etc) until you've reversed what you know you did with the mixture adjustment. Think about what's happenning when you turn the adjuster: it's right hand thread; visualize looking at it from under the car while you turn it clockwise, you will be raising the jet and in its center is a tapered needle extending in it from above, as you raise the jet, less fuel can flow through the jet/needle so you are leaning the mixture. Get back on track by leaning (engine off) each jet in until it stops the out two turns. Good luck. DAW Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 26, 2002 Share Posted February 26, 2002 Originally posted by DAW:Do a search of this site for SU adjustment tips. I know I responded several months ago to a similar post. First of all, don't do anything else (timing, etc) until you've reversed what you know you did with the mixture adjustment. Think about what's happenning when you turn the adjuster: it's right hand thread; visualize looking at it from under the car while you turn it clockwise, you will be raising the jet and in its center is a tapered needle extending in it from above, as you raise the jet, less fuel can flow through the jet/needle so you are leaning the mixture. Get back on track by leaning (engine off) each jet in until it stops the out two turns. Good luck. DAW Yea I did that already but it seems like its still not working peoperly. It runs great when cold then just dies out. Hopefully when I receive that video from Ztherapy that will help. Quote Link to comment Share on other sites More sharing options...
DAW Posted February 26, 2002 Share Posted February 26, 2002 I searched back too but it didn't come up. In it I recommended a book, "How to Build & Power Tune SU Carburettors" by Des Hammill, published by SpeedPro series. The Z Therapy video will be a great help too. When you say it runs fine when cold, do you mean with the chokes on or off? The chokes on these carbs is a linkage that mechanically pulls down the jet from the needle (like backing out the knurled mixture adjustment, except exaggerated). The choke linkage at the carb can stick, leaving the carb way too rich once engine is warmed. DAW Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 28, 2002 Share Posted February 28, 2002 Originally posted by DAW:I searched back too but it didn't come up. In it I recommended a book, "How to Build & Power Tune SU Carburettors" by Des Hammill, published by SpeedPro series. The Z Therapy video will be a great help too. When you say it runs fine when cold, do you mean with the chokes on or off? The chokes on these carbs is a linkage that mechanically pulls down the jet from the needle (like backing out the knurled mixture adjustment, except exaggerated). The choke linkage at the carb can stick, leaving the carb way too rich once engine is warmed. DAW I can't tell If its sticking. I brought it to a mechanic who supposedly works on Z's and they have had it for 2 days and can't figure it out. It starts up fine cold and as soon as it warms up it bogs and dies. I am getting frustrated and I am about to order the rebuilt carbs from Ztherapy. I have never replaced any carbs before is pretty simple? What tools do I need or extra parts are involved such as gaskets etc...I am sure its the carbs that is the problem because it ran fine till I adjusted the mixture settings underneath the Su's. Any more input appreciated. ShredZ Quote Link to comment Share on other sites More sharing options...
Guest Zpeed Posted March 3, 2002 Share Posted March 3, 2002 get carb cleaner and clean the jets inside the float bowl, make sure u clean them really really well... i cleaned them and now my carbs work perfect... Quote Link to comment Share on other sites More sharing options...
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