'86 nissan 720 Flat spot off idle

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NorCalNissan720
Posts: 3
Joined: Tue Mar 09, 2021 4:19 pm
Car: 1986 Nissan 720 2.4L 5spd
1973 Datsun 240Z

'86 nissan 720 Flat spot off idle

Postby NorCalNissan720 » Thu Mar 25, 2021 5:12 am

Hopefully get some help here. This forum doesn't seem so busy. I have an 86 nissan 720, Z24 engine. California model. I've gone through it to make sure I don't have vacuum leak, have rebuilt the carburetor too. The issue is I have to feather the gas off idle or it wants to die, like hitting a flat spot/going lean.

Float level is correct
Accelerator pump squirt not the greatest, but it's there
No vac leaks
Choke works properly
Idle cut solenoid works properly

Any ideas? I know even a rich condition can cause this as can a lean issue, so maybe lower float level a little more?


User avatar
VStar650CL
Posts: 2002
Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

Re: '86 nissan 720 Flat spot off idle

Postby VStar650CL » Thu Mar 25, 2021 5:26 am

If you're unsure rich or lean, pop a spark plug and take a look at the burn. Medium tan to cocoa brown is healthy, dark brown to black is rich (or cold), light tan to white is lean (or hot).

NorCalNissan720
Posts: 3
Joined: Tue Mar 09, 2021 4:19 pm
Car: 1986 Nissan 720 2.4L 5spd
1973 Datsun 240Z

Re: '86 nissan 720 Flat spot off idle

Postby NorCalNissan720 » Thu Mar 25, 2021 12:33 pm

Already did, little bit white on the edge of the tip, rest is brown. White part was tan. Looked healthy to me.

Also did some squirts of carb cleaner in the throat of the carb; too much kills it at idle, but quick sprays doesn't affect it much. If lean, it would speed up or smooth out. Hmm, did that with the straw on. Probably better idea without it.


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