Sergio146 Posted August 21, 2021 Report Share Posted August 21, 2021 For my 1980 Datsun 720, whenever I start it in the morning, the rpms stay around 1200 but when it is fully warmed up, it ramps up to 2000 rpm. Is anybody familiar with adjusting a hitachi carb since I have finally managed it to make it run. Thanks. 1 Quote Link to comment
datzenmike Posted August 21, 2021 Report Share Posted August 21, 2021 It increases by itself? or when you start to drive it??? 1 Quote Link to comment
Sergio146 Posted August 21, 2021 Author Report Share Posted August 21, 2021 It increases by itself when it is simply idling when I first start the truck and allow it to fully warm up. 1 Quote Link to comment
datzenmike Posted August 21, 2021 Report Share Posted August 21, 2021 When warmed up, at least 10-15 min take the top of the air filter. Is the choke flap vertical and fully off? 1 Quote Link to comment
Sergio146 Posted August 21, 2021 Author Report Share Posted August 21, 2021 The choke flap is vertical, not sure what you mean by fully off? But if it refers to being fully up, then yes it is up. 1 Quote Link to comment
datzenmike Posted August 21, 2021 Report Share Posted August 21, 2021 Choke is on when closed and off when vertical or open. How about the fast idle cam? This is when the engine is cold and the plastic cam moves into position and stops the throttle closing forcing a fast idle. As the choke warms and opens the cam moves out of the way and the idle drops. 1 Quote Link to comment
Sergio146 Posted August 21, 2021 Author Report Share Posted August 21, 2021 Oh I see, I'll look into that and keep you updated on whether it doesn't seem right. 1 Quote Link to comment
datzenmike Posted August 21, 2021 Report Share Posted August 21, 2021 Hold the throttle part open and open and close the choke flap by hand. The fast idle cam should lift up and drop down freely. WD-40 spray will wash dirt off of and lubricate it. 1 Quote Link to comment
Sergio146 Posted August 21, 2021 Author Report Share Posted August 21, 2021 OK, I have looked at the fast idle cam and by just looking at it, the adjusting screw is not sitting on any of the steps. 1 Quote Link to comment
Sergio146 Posted August 21, 2021 Author Report Share Posted August 21, 2021 How do I go about adjusting it. Is there a certain way to adjust it or just until the screw lands on the last step? 1 Quote Link to comment
datzenmike Posted August 21, 2021 Report Share Posted August 21, 2021 No don't mess with it. It's set at the factory. Hold the throttle part open and close the choke plate. The cam should lift up and the screw will sit on one of the steps. If it does it can be presumed that the choke is working properly Can you turn the idle speed screw down when it's revved up? 1 Quote Link to comment
Sergio146 Posted August 22, 2021 Author Report Share Posted August 22, 2021 It won't turn on at all and the fast idle cam doesn't sit in anyone the teeth. Quote Link to comment
Sergio146 Posted August 22, 2021 Author Report Share Posted August 22, 2021 *doesn't sin on any teeth of the fast idle cam Quote Link to comment
Sergio146 Posted August 22, 2021 Author Report Share Posted August 22, 2021 What if the fast idle cam has been adjusted already by the previous owner? Can it be readjusted or not? Quote Link to comment
datzenmike Posted August 22, 2021 Report Share Posted August 22, 2021 Very unlikely the fast idle cam was messed with. It's practically impossible to get at with the carburetor on the vehicle. I wouldn't worry about it. You said it revs to 2K so loosen the idle speed screw and try to lower the idle speed. 1 Quote Link to comment
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