1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

strange running condition

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Old 05-05-18, 07:30 PM
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strange running condition

85 distributor/coils spark wires(new)
13b s4 6 port, no air restriction sleeves
Racing beat intake with Mikuni carburetor(similar to weber)
vacuum advance hooked up

bought this engine used and assembled it with all new internal parts, I checked all the jet sizes in the carburetor, all good. timing is set. fuel pressure at 4psi. fuel filter clean. ive fiddled with idle and float a bit but not much change was shown.

if I let it idle then give it acceleration it will rev high but if I go to rev again it tries to die. ive clwaned the carburetor with carb cleaner etc but next im going to inspect every jet closely for cleaning.

what do you guys think based off the videos?
https://youtu.be/9xk_OcijmIU
https://youtu.be/T1k9EBo8izU
Old 05-05-18, 07:41 PM
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I actually own Rotaries

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sounds like your running on 1 rotor to me
Old 05-05-18, 08:09 PM
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Originally Posted by 73rx313b
sounds like your running on 1 rotor to me
maybe one side of the carburetor is clogged
Old 05-05-18, 11:33 PM
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That’s not how carbed intakes work bro.
Old 05-06-18, 07:48 AM
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The sleeves that you're talking about are not air restriction sleeves. They are opened by actuators at higher rpm's to allow addition air into the engine that is subsequently stored in the dynamic chamber. The engine is designed to run using all of the components for the 6 port system. Is the intake manifold built for the S4 N/A 6 port engine?

It almost sounds like the engine is not getting enough fuel. Its choking at any heave ounce of throttle application. Why is your fuel pressure at 4psi? I would think at least 6psi would be in a good operating range.
Old 05-06-18, 07:23 PM
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Not sure about that set-up exactly, but IMHO it sounds like the accelerator pump is miss-adjusted. I had a similar problem, but it was the Nikki's vent solenoid having died that caused the bowls to be under high vacuum under load. Out of curiosity, have you checked timing?
Old 05-07-18, 09:17 AM
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Originally Posted by Benjamin4456
Not sure about that set-up exactly, but IMHO it sounds like the accelerator pump is miss-adjusted. I had a similar problem, but it was the Nikki's vent solenoid having died that caused the bowls to be under high vacuum under load. Out of curiosity, have you checked timing?
thats what many are pointing me twords, the diaphram is in good condition maybe there is an adjustment or the spring is worn out.
Old 05-07-18, 09:45 AM
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Again, not sure about the Mikuni, but can you see the AP nozzels? If so, while the car is off pump the gas a couple times and see if fuel comes squirting out of them. It should be a decent amount and if there isn't any, something in the circut is most likely clogged. It could also be out of adjustment or the spring could be missing or installed on the wrong side of the diagram like you said.

Keep us posted.
Old 05-10-18, 12:02 AM
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Originally Posted by Benjamin4456
Again, not sure about the Mikuni, but can you see the AP nozzels? If so, while the car is off pump the gas a couple times and see if fuel comes squirting out of them. It should be a decent amount and if there isn't any, something in the circut is most likely clogged. It could also be out of adjustment or the spring could be missing or installed on the wrong side of the diagram like you said.

Keep us posted.
rotorholic helped me troubleshoot the issue and found that my Main Air jets are too big, this led to the issue of trying to die at 4k rpm when the main jets kicked in and let in too much air. the main air is a part of the main jet circuit.
Old 05-10-18, 08:20 AM
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Awesome. Nice to hear you got your problem sorted out.
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