gmkeegan Posted April 28, 2016 Report Share Posted April 28, 2016 hi guys so i bought a 1971 240Z first thing i did was take the carbs off and give them a new rebuild kit! put them back on the car and it runs idles but when i hit the throttle it bogs or backfires then i know it's too rich..... so i lean it out and it still bogs... i read online if it's too rich and you lift the float it will revs up. but mine bogs down. can anyone help? oh last thing some of my emissions hoses are cracked and not connected does will that cause for a bad tune? Quote Link to comment
Doctor510 Posted April 28, 2016 Report Share Posted April 28, 2016 Sounds like the float levels are wrong. Be sure you are using ATF or Marvel Mystery Oil in the piston dampers. Your chokes may be sticking DOWN if you used them. Quote Link to comment
gmkeegan Posted April 28, 2016 Author Report Share Posted April 28, 2016 Sounds like the float levels are wrong. Be sure you are using ATF or Marvel Mystery Oil in the piston dampers. Your chokes may be sticking DOWN if you used them. omg i totally dumped the one side out by accident.. i'm going to refill it tomorrow and tell you how it goes thanks again!! Quote Link to comment
datzenmike Posted April 28, 2016 Report Share Posted April 28, 2016 Backfire can be from too lean. Did you refill the dampers with oil? The dampers delay the opening forcing a slightly richer mixture on sudden acceleration. 1 Quote Link to comment
gmkeegan Posted April 28, 2016 Author Report Share Posted April 28, 2016 Backfire can be from too lean. Did you refill the dampers with oil? The dampers delay the opening forcing a slightly richer mixture on sudden acceleration. when cleaning the one carb i dumped out the oil by mistake i am going to try tomorrow and tell you how it goes. too dark now. thanks again!! 1 Quote Link to comment
datzenmike Posted April 28, 2016 Report Share Posted April 28, 2016 It's the viscosity that slows the sudden opening of the slide. Some like ATF but it's too thin. It doesn't really have a weight rating and it varies between makers. For above 40-50F maybe try 20w40 engine oil and increase it in stages till you get what you want? Quote Link to comment
Mr.Dean_Yates Posted May 10, 2016 Report Share Posted May 10, 2016 Down here in az atf is all I ever ran in my su carbs. Thing ran like a stuck pig. I think altitude has a factor...just a thought. I went up the mountain in Tucson (considerable altitude change of a couple thousand feet) and when I got towards the top it started to bog and sputter and sound like crap. Probably cause I ran atf. I messed with those carbs for about two hours trying to get it to run smooth again but no luck. 1 Quote Link to comment
MikeRL411 Posted May 17, 2016 Report Share Posted May 17, 2016 Actually old "3 in 1" oil sems to be just right! Singer sewing machine oil would be a good substitute also, Of course there is the seldom exercised option of using the manufacturers specified damper oil, but WTF! this is RATSUN! 1 Quote Link to comment
datsunwizard Posted May 17, 2016 Report Share Posted May 17, 2016 Or if you want the correct oil, go to a British part house, and get the original. Comes in a neat, easily to use bottle. 1 Quote Link to comment
Doctor510 Posted May 17, 2016 Report Share Posted May 17, 2016 My preference is Marvel Mystery Oil (MMO) Quote Link to comment
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