Carburetor change?
 

Whatever problem the Nikki has,fix it and keep it. Cobbling a 2V Holley carb and adapter plate together is essentially going backwards both from a driveability and a performance standpoint. What is your purpose in going this route?
What's the story on the Dart in the background?

I'm just trying to figure out how he's going to get a 2V carb to work on a 4 port manifold...…. :scratch:


But yeah, 100% backwards direction. And how do you figure its difficult to work on a nikki compared to a holley? And who is selling new Nikki four barrel carbs?


No no no this doesn't add up at all. I'm calling trolling; you had me going. :lol:

But I would like to say if you do go with a 2 barrel carb keep us posted. That'll put my redneckery in check.

The O'Reillys carb will not be new,it will be a reman. I was not aware they sold or could even get reman Nikki carbs. I have no idea of the quality of them,or how long it would take to order one in. Since you find your Nikki hard to work on,either find someone to rebuild it for you or use yours as a core for the O'Reillys reman.The Nikki was designed for the rotary engine while the Holley,any Holley is not. Trying to make any 2V carb work on a rotary will be a futile effort.

Now the Weber is a much better choice. You'll want to add a header for the exhaust to make it come alive.

Lots of guys go with webbers or IDA or other single throat carbs. That's pricy IMPO.

What's wrong with the nikki?

Before you toss it in the trash try unscrewing the 9 bolts that hold the top on (I'm just recalling that number from memory), and peek down inside. Take a can of carb cleaner with you and try not to mess with the floats (cause they are the devil to reset). Spray the carb cleaner down each of the little holes (they are the air bleeds). Then take the straw from the can of carb cleaner and stick it down in the fuel jets they are at the bottom of the v in the middle of the bowels on either side of the carb.

This process will dislodge most anything in the carb that will cause it to not deliver fuel at anything other than idle. Try this before you toss your hands up and let a simple carb kick your butt. ;)

The ONLY part of the Nikki that is a pain to work on is the idle circuit. Just because it is cast into the base plate, but it doesn't often get that clogged.

Boom, there is your problem.

Your solution is to either put the old seats/floats and needles back in, or take the seats and needles out and burnish them.

The new kits (much like new Webber carbs and Holley carbs) are made cheaply quickly, and they have lots of rough edges. Smoothing the roughness off the new needles will make them not stick in the seats.

Right on! This is exactly your issue. Did you rebuild it or get it done or it came that way? Doesn't matter, do what was suggested. Also is it an OEM fuel pump or after market? The nikki only likes to see 2.5 psi max fuel pressure. That will cause flooding also.

Mine would flood at 3psi or higher, and stop flooding at a hair under 3 (literally a hair, like 2.9) Also, you mentioned removing the rat's nest. If you also cleaned up your wiring you want to keep an ignition-hot 12v on the Air Vent Solenoid plug. Without it you'll get flooding issues. Hard to see but I used some of the left-over wiring I stripped out and made a little 3-plug pigtail to plug inline with the temp sensor connectors.

https://cimg9.ibsrv.net/gimg/www.rx7...fe2ccb4f24.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...4f01d5c9e8.jpg

Nothing at all wrong with a Nikki. Just have to learn them.

They're not complicated, for a carb.

The photos are accurate, as in, that is my car. The notes on the Mazda pictures sound right. I used this guide for the stripping -
http://foxed.ca/rx-7/Carb%20Stripping%20Draft%201.pdf
The only parts to be careful with are -
*Removing the choke butterfly: Don't do it if you plan on ever starting the car below 55 Degrees F
*Goobering up the vacuum holes with JBWeld. Yuck! I made blockoff plates/gaskets for anything I opened up, so that I or the next owner can restore it to stock.
*Removing the Dashpot. Unlike an Edelbrock or Holley, the Nikki will stall you out if you stop short (mine did/does anyway). The stripping guide says to learn some finesse when stopping. Fuck that - you end up stalling in every intersection. Put the Dashpot back on and your fine again. That was my experience, YMMV.

If your Air Vent Solenoid wires are cut that is why you're flooding. ***Someone with more experience than me please chime in here.*** It's my understanding that if the car is running, that valve needs to be open for air/vapor/fuel flow to work right. It needs 12v to it to stay open. Cut the wires and it is stuck shut, which causes flooding. I think this part is still available and affordable.

Try Atkins Rotary, Racing Beat, Google, Ebay, I don't know. One of the last sections in that stripping guide is about removing this, and it seems tricky. I took some better pictures of my OE/stripped/Sterling-modded intake and the pigtail I made for powering the vent solenoid. The last picture shows the water temp sensor plugs I connected to, to power the solenoid. These OE wires send the signal from the temp sensor to the choke knob, so your factory choke operates. It's hot with the ignition and right there, so I tapped into it. I never saw this done, so thought I'd post what I did. This last pic shows an Edelbrock carb (which I don't recommend) but shows where I get power for Eddy/Holley carb electric chokes. #1- factory plug in harness #2- Factory temp sensor plug #3 my wire to aftermarket electric chokes.

https://cimg0.ibsrv.net/gimg/www.rx7...65345c1bb9.jpg
https://cimg0.ibsrv.net/gimg/www.rx7...2bfcf2f4c3.jpg
https://cimg4.ibsrv.net/gimg/www.rx7...ea0e978074.jpg
For a Nikki you want 2.5 to 3psi (max). Not sure the best regulator to use, other than a stock pump and no regulator. I used / tried an NX low pressure regulator rated at 1.5 to 11 psi, but at 3psi the adjusting screw literally screwed out. I had to use Thread locker to hold it in one thread, so I don't recommend that brand.

Oh, I had to tap into the wiring because I removed a Lot of the OE wiring harness when I ditched the rat's nest. You may still have the correct plug in your car.

https://cimg5.ibsrv.net/gimg/www.rx7...ea998d5e9a.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...972d59dae9.jpg
No wonder these cars are so heavy!

ive done some fuel system testing, and the short answer is that you want no regulator.

the regulator you do not want is the holley, it kills fuel flow and pressure is all over the place

the stock pump, flows quite well, and pressure is rock solid at 2.75psi.

if you must change stuff, i like the mallory pump, it fits the car well, and has a regulator in it that actually works

J9 good info as always. Which Mallory is that?

I think he's talking about this Mallory pump. Mallory/MSD 4070M Fuel Pump for RX7 1975-1985 - Racing Beat

I like the Mallory 4309 fpr they sell. Mallory/MSD 4309 Fuel Pressure Regulator for RX7 1975-1985 - Racing Beat

I'd pull the vent solenoid out and cut the plunger off of it. At least that's what I did to my carb.... Seems asinine to power something that will cause your carb to fail to restrict fuel; when its original purpose for existence is no longer there.

BUT if it works hey why not slap it back in and turn the key.

Carter, the wire you circled in black is the richer solenoid and is not needed if you've already removed the emissions junk. Have you stripped wiring and emissions from the engine, or is it still there?. The solenoid on the fuel side (driver's side) is the air vent solenoid I was speaking about. If it is in there it needs power or your carb floods. This is all in the carb stripping guide I linked a few posts back. When I did mine I didn't want to do any irreversible damage, so I just powered it as the guide suggested. To remove it you have to break it out and I didn't want that.

Hook it up if you desire. That can confirm that this is your problem. I think it is, and also in combination with maladjusted/new floats.

I never followed a "stripping guide". I'm sure its helpful, but I just went through the carb and took "unnecessary bits" off. Unfortunately that means I can't tell you 100% what I disconnected. However I can say that if I ran into a solenoid that caused flooding I can guarantee I "solved" the problem; this typically means I cut the plunger off the valve on the inside of the part.

I've done just about everything you can do to these carbs and I do remove the float bowl vent solenoid on most of them for reduction of things that could go wrong.

yeah that one. if you had a stock engine though i see no reason to change the pump at all, it flows plenty

no idea, you'd have to test it.

test 1 is easy, its just volume. so find a container with some kind of measurements on the side, mine is for juice and its labeled in Milliliters. Mazda's spec is cc/minute so this is nice. take the fuel link off the carb, put it in the container, and run the fuel pump for 30 seconds. Mazda's spec is 1400cc/minute or more.

test 2 is to put a pressure gauge on it, but you need a 0-5psi one and the bigger the better. those little 0-15psi ones lack resolution. stock pump does 2.75psi and its steady as a rock.

Jerry can will fix the no fuel issue. :lol:

Very interesting. I am working on an EFI upgrade with a DCOE style throttle body. I was actually thinking of working the dashpot into the linkage for a smoother off throttle experience. Not sure I can fit it, but I'm going to try.

I never use the dashpot and things run fine.

a stupid question>>>-->Do carburetors wear out? A mazda dealer mechanic told me such.

The shafts can. They will make a vacuum leak.

Any reason to omit the dashpot? Is it a just a choice for simplification? Not trying to thread-jack, just curious since I'm doing a full carb build and I'm looking at simplifying (improving) everything possible. Does removing it not cause issues with the throttle snapping shut and such, or does it simply require more finesse?

Gotta be honest I had to google search what a dash pot was... Nope, apparently its unnecessary cause I've never had any issues without it.

Awesome, one less thing to clean up and install on my stripped carb. I had never tested without it before and seeing how it's there in the first place, I'd say it's reasonable to have figured it had some purpose to serve. Nice to know it's not necessary.

Thanks

If you look it up some say it was to prevent stalling, others will say it was specifically emissions related (despite them existing before emissions was an issue). I think it would likely be most useful in traffic, cruising at 10-15 mph in 2nd gear. Lifting off the throttle as you try to modulate speed without it may cause a slight shutter and bucking, while having it will produce a smoother deceleration transition. So you can remove it...but why?

Yeah, that does make sense. I've seen people who say to remove it and those who don't. I would agree that it has little to do with emissions, as I can't see how closing the throttle plates slower would affect that.

Perhaps once I get the carb installed I'll do some testing with and without it. I had wondered about slow traffic throttle work (going between brake and gas more often than normal at low speeds), so I can see where that might cause some issues. Again, I didn't want to thread-jack, but thanks to everyone who replied to my comment.