Background; 1983 12A, bought 2 years ago, has never run properly. We had installed new wiring set, new distributor cap, rotor and NGK plugs without a fix. Decided it must be the carb and so disassembled, cleaned, and all new gaskets were installed, again without a fix to the sputter. Removed the rats nest, capped of all the vacuum ports except for one used to drive the vacuum advance system and the crankcase vent system. Finally gave up and took the car to the local rotary guru who did a compression test and pronounced the engine in good health, but did not fix the problem. After many months, I gave up again and took the car to a fellow down the street who told he had worked on these a few times over the years. Finally, a fix to the problem.

Problem: This engine would run fine under load, not ever at idle or cruise, sputtered.

Solution; The mechanic used a Propane Bottle and a long rubber hose to detect and pin point the location of vacuum leaks. This was done by letting the engine idle, then placing the hose outlet near a possible leak point and then slowly opening the shutoff valve on the bottle. If the engine smoothed out he knew he had a leak point.

The result: He discovered a small plate that was installed on the back of the intake manifold to be held on with two fasteners, a bolt and a nut threaded on to a stud. The stud thread was not long enough for the nut to press against the plate. He removed the stud and installed the proper size bolt to seal off the open port. I might add the plate was supplied as part of a kit that came with the Racing Beat exhaust header.

I had removed the Shutter valve and plugged the shaft and valve port using two wooden plugs. They leak, not a lot, but enough to cause a problem. This was fixed using a coating of two part epoxy.

The last leak point was a tube port that had been left open on the carburetor. This was capped off using a rubber cap.

Tuning: Adjustments were made to the one Nikki adjustment and what is interesting, is that the adjustments were very effective where before you could turn the adjusting screw several times with very minimal effect.

Finally a great running engine!! God, how beautiful the sound of a smooth running rotary.

Best regards,
THC

 

Propane Bottle? I haven't heard of that one, that's interesting.

Congrats, I'm glad ya got 'er work'n the way she should.

 

If you supply a little propane near a vacuum leak it gets sucked into the engine and the RPM goes up a little. Gotta be careful, though. The Propane is flammable, and I think that's why some use a long hose rather than just pointing the nozzle. Hope it works.

B

 

Mine still sputters. Good that your's doesn't now.

 

The acv plate (on the back of the intake mani) can be a bitch to get sealed sometimes. I broke the stud when removing it and had to drill and retap for a bolt. That thing is such a pain.