Just pulled my car (80 RX7) out from winter storage and managed to get it started. That's the good news. It idles at about 550, but that's not my choice, it's the car's choice. The idle speed and mixture screws don't have much effect at all--other than finally stalling the car out. It's 550 rpm or nothing. What is preventing me from even playing with the idle?

I've searched through the archives and looked Sterling's Web pages, but I just end up getting confused. Thanks for anything you're willing to toss my way.

 

Are you sure you are adjusting the speed screw and not just the mixture one? I hate to ask that but its happened alot in the past. Of course, SA's had a different screw setup than FB's... Are they right next to each other or is there just the one in the middle?

 

this is a first for me, i'm interested in the results lol

 

There are two screws, one above the other. The top screw is the speed adjustment and the bottom is the mixture (according to the manual). With the speed screw turned out about 2 turns or so and the mixture screw turned out about 5-8 turns (seems like a lot), I can get the car to idle, but just barely---and that's at 550 with no other choice and it seems like the car is on the verge of stalling all the time.

The other thing that is happening that might be a clue is that it starts right up when it's cold, but then is difficult to start when it is warm.

Thanks for the help.

 

Nope, idle adjustment screw will be to the rear of those two screws, closer to the throttle cable.

Head over to www.sterlingmetalworks.com for detailed instructions on tuning the idle. Great site!



.

 

so the nikki is the same for SA and FB?

 

No, SA's were different in the screw locations. My Haynes manual pictures an SA carb. I had a hell of a time figuring out where the speed screw was when I first started since my carb didnt have the 2nd screw to adjust lol.

 

Hope I'm not repeating myself here--my original message just disappeared, so I'm taking another shot at this.

I've attached a photo of my carb which I have just pulled. I'm still trying to figure out the idle issue, which means I'm also still trying to figure out where the adjustment screws are.

In the picture you will see two screws just above where the red plastic handle of the screwdriver begins. According to the manual, the top screw (slotted) is the idle speed. The bottom screw (phillips) is idle mixture. But I trust you guys more than the manual. What's what? Am I totally missing something?

And what's that phillips screw to the right with the little blotch of red paint under it?

Thanks a ton.

 

phillips screw with red blotch is the Idle speed screw the other two would be
the air/fuel mixture

 

Sorry for misinformation. I keep trying to prove Kentetsu wrong but its too damn hard!

lol

 

that funny that you have an alien as your sig pic. Im from roswell NM and because they crashed here 1947 that our main attraction. As for kentetsu hes your post superior its like going against your samurai master its just unheard of.

 

Thanks for the help. It's wild. I looked hard for the idle speed screw but didn't see it until I pulled the carb. Hopefully, this will help me get on track with the idle. But now that I have the carb pulled, what would you guys suggest I do while I have it out of the car?

 

Come on Ian, it can't be that hard! I'm wrong at least .003% of the time...

Glad you're getting things figured out. Have you checked out the website I posted? You'll learn more than you ever wanted about your carb over at Sterling's place...

 

Since this happened post-storage, my guess is that you've got an air bleed that's clogged. Doing a proper cleanout of the carb would probably be useful.

SA adjust screws are indeed different from the later FB's. There are three main ones that impact idle, only two of which (idle speed, also known as 'Air Adjustment Screw' or 'AAS,' and idle mix, also known as 'Mixture Adjustment Screw,' or 'MAS') can/should be adjusted while the carb is on the car.



The third, the 'initial throttle opening' screw, normally doesn't need adjusting, and it is locked with a locknut and inaccessible when the carb is on the car. Initial Throttle Opening can only be set using a feeler guage or dial guage, from the bottom of the carb.

(Adjusting ITO via dial guage)

 

Yep, I checked it out, and hanks for the tip. It has great info.

Things are looking up. The car is now idling at about 1200 (can't seem to get it down to 750--850), but at least it is now running. She fires right up on a cold start, but doesn't want to start when she's warm. If you have any idea what might going on, I'm all ears--in the meantime I'll be searching through the archives.

Really appreciate the help!

 

Divin Driver,

Thanks for the great photos and the info. I was able to mess with the 'initial throttle opening' screw but it was pure guesswork, and now seems like a mistake. On the other hand, the car is now running, but it seems like I should take the carb back off and do a proper adjustment with a guage.

 

I used a dial guage to set mine, as I couldn't locate a small-enough round feeler guage (the ITO is tiny, a matter of thousandths).

If jimmying it got you running, it's clearly a mixture issue; carb adjustment, jet and air bleed cleanout, or similar.

Doing a carb rebuild might be your best bet; gets everything clean, and properly adjusted.

 

I'm seeing that the idle speed control screw is not the stock screw and the nut is on the wrong side, so someone has already messed with it, probably during the rebuild (non-stock gasket color). This was almost certainly your initial idle speed problem.
As for the no - hot - start issue, this can be the result of a fuel system ventilation issue; ie the charcoal canister stuff. Too much condensation mixed up with oil vapors, clogging the vent with dino-pudding. Maybe a clogged/busted PCV valve, or lack of one. I am uncertain yet whether this has the effect of flooding the idle circuit, which is basically gravity fed, or depleting the supply, or perhaps the supply is depleted as the fuel in the tank cools & contracts, sucking the fuel in the supply line backwards toward the tank. Not really sure. There's a small chance it could be your float bowl ventilation solenoid (not being hooked up), but the lack of ventilation within the carb usually wreaks very different havoc. Usually tank venting issues will give a tell-tale "whoosh" when the fuel cap is removed after a good heat up.

So for the idle, you're idle speed screw is too far in, keeping the primary valves too far open, thus causing the idle mixture adjustment screws to have virtually no effect. (You're nearly idling off the main circuit.)

For the hot start issue, try going comando with the tank vent line.

 

Looks like a stock idle speed control screw to me. Not all Nikkis came with a spring loaded screw.

 

It's not. It's a Nikki screw, but it's not the idle screw.
The locking nut is also supposed to be on the other side.
...But who knows? I've only taken about 300 of them apart. :shrug:

 

-Yup, I'm wrong and I was a putz with that remark.
The nut is on the correct side. The screw probably is the correct screw, though I usually see these in a harder steel than the other Nikki screws, and slotted, not Phillips.
I change them on the Sterlings that have early throttle bodies by removing the nut and using the throttle sensor positioner screw spring from the OMP link so that it's set up like the spring-locked bullet style idle speed screws on the later Nikkis.

 

Thanks, guys. A lot of info. Not sure where to go from here. Maybe a carb rebuild. Maybe a carb clean. Maybe a local mechanic--there's one in Boise, Idaho who claims to have a lot of experience with the rotary, but maybe that's just the easy way out. Just have to give it some thought and monkey with it some more--but in the end I want an RX7 that runs right.

 

That's a relief... 'cause mine's always been set up that same way (nut out, no spring, slotted philips). It is a different steel from the other screws; seems very hard. Also a very fine pitch to it.

Being the 2nd owner, though, I couldn't swear that someone else didn't get to it before I bought it.

 

When I run across a carb with a short screw and locknut like that, I usually replace it with the longer harder steel slotted springloaded screws from dead FB Nikkis. It makes adjustments so much easier.

 

[ offtopic ]
Jeff, you got any good SA carbs or even just bowl covers laying around, with working power valve pistons?
I could make a home for one...

[ /offtopic ]