I just rebuilt the Nikki on my 84 FB, and now the bitch won't idle! I digress, a little background, the car was sitting for 3+ years, I did the normal stuff, oil, filter, pulled the plugs, spun it by hand, blah, blah, blah...I drained/pulled/cleaned/reinstalled/filled the tank (fresh gas), new pump, new filter, pulled the carb, cleaned, soaked, and rebuilt it, but I think the idle circuit is still gummy. It runs great but won't idle. When I first got it running, the idle mixture screw had no affect on idle at all, the only way it would idle is at around 1200, and I'm guessing at that point it's probably out of the idle circuit, and into the primary circuit. I pulled the mix screw, hosed the idle mix hole down with carb cleaner, and the mixture screw started to make a difference, I revved it up and tried to almost choke it out, trying to suck the idle circuit clean, to no avail. Once in a while, if I babysit the throttle, all the way down, I can get it to idle, but the first time you crack the throttle, it comes back down and dies. I'm starting to wonder if maybe someone put some sugar in the gas tank before I got it, because the inlet and return were choked solid, for the first 4 inches up the pipe, inside the tank. I made sure I cleaned everything and even rinsed the tank in a half gallon of denatured alcohol, ran a half gallon of clean gas through the pump, and lines. My big question is, what is the correct setting (or at least a good starting point) for the mixture screw? Could I have a decel valve sticking? If you shoot carb cleaner in it running, it tries to die. I bead blasted the plugs, before I started it, they were pretty black, could this be the source of my low idle woes? I did pick up new plugs for it, probably won't go in until Sat. night though. I'm also going to change the fuel filter again, when I do the plugs, just for good measure. Hook a brother up! Any help at this point would be appreciated.

Pat

 

Welcome to the forum and the Darkside. In my sig line is a link to the FSMs, factory carb manual and other rotary related reading. DL whatever you need and read up. In the FAQs, Sterling has some great writeups on troubleshooting Nikkis. High idle is generally a sign of a vacuum leak, I would start there. As for the idle mix screw screw, 3-1/2 turns out is a good starting point.
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Thanks for the reply, and the welcome. I'll try the 3-1/2 turns, I started out at 2-1/2, and progressed to 4-1/2, where it seemed to smooth out. The only reason its idling high right now, is because when I go any lower it dies, which is why I thought it must be idling above the idle circuit, into the primaries. I'll check the Faq, and the tips, I checked the factory manual, and the only thing it said about the idle mixture setting is, use an EGA to set it. Thanks again for the reply.

Pat

 

Check for vacuum leaks...

 

yeah, sounds like the mystery hose, n201-13-756?

 

I have checked for vacuum leaks, sprayed the entire outside of the carb down, I'm pretty confident there are no vacuum leaks, I have turned the idle up, because it won't stay running (for long) at 750. I am wondering if one of the solenoids in the "rats nest" is sticking open. Like I said above, occasionally, if I baby it all the way down, it'll idle but after you rev it, it comes down and dies. Hey Kentetsu, I just moved back to AZ. from Battle Creek (just noticed your loc.).

 

Funny, I moved from Arizona to Michigan.

Personally, I think that spraying carb cleaner around looking for vacuum leaks is an urban myth. What happens when you spray it into the car? The engine wants to die, not rev up. Pointless. There are only so many vacuum lines on the engine. It may seem like a lot, but if you go through them methodically you will find something. Sometimes the best way is to start replacing them with new lines. Tedious, I know, but it can work.

Even I had a vacuum leak that evaded me for over a year. It turned out to be a broken vacuum cap. This was on an engine that had the rat's nest removed, so there were only like six or eight lines to deal with. I didn't identify the leak until I removed the carb and replaced the intake gasket. As I was remounting the intake onto the engine, I saw the cracked cap. Big difference once it was replaced.

Good luck with your car. I wish I was back in Arizona, but I just have too many roots laid down in Michigan now to move. Maybe when I retire? lol. Enjoy the sunshine!