Datsun Roadster Forum-311s.org

Hi ! Hope someone can help me because I'm at wits end with this roadster and I thought I had at least some kind of mechanical abilities !! The car runs rough when idling at cold start up with choke partially out and when I go to push the choke all the way in once It should be warm enough to do so it backfires through the exhaust then dies ! I'VE TRIED ALMOST EVERYTHING !! Almost everything in the ignition is new and the carburetors were rebuilt by Apple Hydraulics !! Any SUGGESTIONS WOULD BE MUCH APPRECIATED !! I've had a mechanic look at it and he didn't help the situation any !!! PLEASE HELP !!! i WILL RESPOND TO ANY SUGGESTIONS ! THANK YOU VERY MUCH FOR THIS MESSAGE BOARD AND THE FINE MEMBERS USING IT !!!

Is yours a 68-70? Does it have the smog pump and air injectors still attached? If so, there's an anti-backfire valve that will prevent the car from backfiring when decelerating. If this piece is bad your car likely will backfire. It might also be bad or misadjusted exhaust valves that aren't holding in the pressure when the air/fuel mixture is ignited.

As for dying when you push the choke in and the car is warm, it sounds like you don't have it rich enough. You should start from a standard tuning setting and then adjust from there. 1.5 full turns of the air/fuel adjustment nut (under the carb body) is a good place to start. Adjust the richness on each a fraction of a turn richer of that nut (down/loosen makes it richer, up/tighten makes it leaner), one carb at a time. See if the idle increases. If so, adjust a fraction richer, etc., until the idle doesn't increase, then adjust it back just a fraction. Do this for each carb.

You also need to set the idle, and this needs to be done on each carb with the dogbones disconnected from the carbs, then the dogbones need to be adjusted so they don't impact the idle once connected. You should NOT use the center idle adjustment screw to set normal idle. That is only for setting "high idle", though what that's good for I don't know either.

But before you do all that, you need to do the basics. Adjust the valves. Set the point gap. Set timing. Make sure your plugs and wires are in good shape. You can't "tune" those by adjusting the carbs and your car will never run properly if those things aren't taken care of first.

I had my car backfire throught the exhaust at high rpms. Sounded like a someone was shooting at me with a rifle next to a wall.
When I changed out the needles to richen it, the problem went away.