85rotarypower

I need some carb help. I started my car a while back and it wouldn't idle. It would only run with the secondaries open. I figured a rebuild would fix this. I got a rebuild kit, and just a few days ago I took the carb off to rebuild it. As I am taking it apart, I notice some differences from the Haynes manual. First off, the choke return diaphram was missing. On top of that, there were a few things messed around with that pertain to the choke. This is a major problem. But, on top of that, as I remove the bolt for the fuel return line, the whole unit slips and destroys the return line fitting. So, instead of trying to salvage a very old and misused carb, I want to install something in place of it.

My options are:

-Get an already rebuilt Nikki carb (don't want to go through breaking something by accident again)
-Get a fairly cheap Holley, Weber, or similar carb and intake.
-Or use a carb from something else (Edelbrock) and make it work.

What is the best option cost wise since I will eventually get a Holley or Weber, but don't want to spend a lot of money?

wwilliam54

junkyard carb + rebuild kit

85rotarypower

Sorry, but no RX-7's in junkyard near me. Only option is to get one from a parts store or from you guys.

wwilliam54

search for the idf thread
that would probly be the least expensive carb besides a nikki

Steve Shulz

What year is your car?

Sterling

What part of the return line did you break?
If you're reffering to the tab with the slot in it that fits over the inlet set square banjo, do't worry about it. Just rip the rest of the tab off the return (careful not to crimp the line). Be certain there ar no pieces of flashing to interfere with the aluminum crush washer when reassebling, and everything will be fine.
If that's not what happened, please specify.

As for the choke, it's virtually impossible to explain how you can make it work without pics for illustration.
I'm in the process of rebuilding a Sterling Carb (modded Nikki) that will have what I reffer to as a "partial choke", Ie, a workable choke without all the extra crap that makes it automatic. The choke will operate but you'll have to hold the **** out the whole time.

(I am working on keeping the switch that engages the magnetic **** holder, but I don't have it down just yet).

I will be taking photos of the whole rebuild in steps so that people can see how the linkages work on a sparkly clean carb.
I don't know if you can wait that long.
But I can say that if those are your only problems, it's not really that bad.

Rx7Carl and I do straight-up rebuilds that include degreasing and airhorn and mainbody sandblasting for a nice clean finished carb. The cost $170.00, shipping included.

85rotarypower

Unfortunately when the tab broke, the whole unit spun and almost broke the return line fitting off the unit. SO needless to say the line is no good. As for choke, I don't think I can get it working. There is just so much missing and things hacked up that I didn't notice before that I will need to replace the carb. I don't think it is worth the effort to get the carb working when in a few months I just planed on replacing it anyway.

BTW, I have an 82' GSL with 5 speed.

85rotarypower

Comon guys, I need help here. What is so special about the Rotary carbs?? Is it just the oil injection, or is there more to it. I would just like to know.

Sterling

I'm not sure what you need to know / are asking.

Richard Miller

you do not want to go to a parts house to get a new carb. Napa wanted something around 400 clams for the stock carb.

Sterling

And that's for a reconditioned carb.

Can you post a picture of the damaged line?

If the choke flap and top linkage is present along with the spring, and the throttle cable bracket is unbent and uncut, the choke can be made to work.

Your next lowest priced option is to search for a carb here from someone. Don't pay more than 40-50 bucks, and expect to have to rebuild it. You already have the new gasket set. It's your best bet -for-the-buck right now if you intend to get a Holley or Weber later anyway.

The Hollys that Racing Beat and MazdaTrix sells are jetted specifically for rotary application.
You can not take a comprable stock Holly or Carter (440cfm) and expect to be able to easily "make it work".

By the questions you are asking about your stock Nikki, my guess is you really don't want to get into trying to make another carb not specifically configured for the rotary to work on your car. (You think you have questions now...!)

Either fix or replace the Nikki, and save your pennies for what you really want, or cough up the dough now.

Do some searching here. Lots of carb info.

85rotarypower

What I am asking is what makes the carb so special that not just any carb can be used on the rotary.

EDIT: sterling, you must type faster than me. You just answered my question in a way. I was asking about things to see if I can just buy a $300 Edelbrock performer carb. Much cheaper than a Holley from racing beat. But then again, you can get the Holley that racing beat sells at Jegs for just under $200USD. Racing beat must do a lot of work to justify their $550 price.

BTW, the return line fitting connected to the main fuel line on the carb is what broke. The tab on top broke and then the line was squashed between the solenoid below it and nearly broke off. It is not reparable. That is of course if I can't find way to hook up a different line. For the cost to get one of those, I might as well just get a carb with a properly working choke.

Sterling

Nothing in particular. It's simply configured (jetted) for the needs of the rotary, that's all. It's basically a Holly knock-off. But Hollys have pressed air jets and metering systems that need to be modified to work correctly a rotary.
Having never compared the rotary-modded Holly to the stock Holly equivalent, I don't know exactly what is done. Carl knows more than I do about them.

The rotary needs a carburetor that works ideally on a piston engine twice its displacement. For example, the 12A has a 70cid displacement, but because it's always intaking on every "stroke", it's "sucking" in as much as a 140cid four, like in a Pinto.
That's just one thing. The other is that the rotary has a redline 25-33% higher than it's usual carbed piston equivalent.
The manifold vacuum measurements are different in a 12a and its piston equivalent, as well. This means that the air jets that bleed vacuum signal to the main circuit need to be different.
Because all carb models and engine models are so different, and nothing is linear when dealing with vacuum, there are not easy reference charts for finding the right combinations of fuel jets and emulsion air jets. Toss in the variables associated with bore size, bore size difference between primaries and secondaries, and secondary opening timing, etc, -It's a matter of trial and error- alot of trial and error.

Sterling

If the main objective here is to get a carb on your car that works until you either make up your mind what you want or get a better carb, you could remove the return line part, reassemble everything, insert a lead fishing wieght into the return line hole, and put that stubby bolt back in.
If the lead ball is big enough, you will seal the opening as it squashes into the hole, and also seal off that tiny orifice on the side.
This is called "deadheading" your return line.

The orifice on the side was Mazdas way of regulating the fuel. The pump (when new) would put out just a tad more pressure than the 4.25 required for the carb (presumably it would!) and it would fluctuate with fuel tank sloshing, electrical accessory use, heat and fuel volume increase, **** like that.
The return hole just kept it more consistant at the carb.

The deadheading idea I just now came up with. Should work. If you have a better idea, try it. Perhaps do what I said but use a longer bolt than the stubby to ensure it reaches the lead ball and squishes it good.
Make certain the ball is barely small enough to fit the line...you don't want it so small that it easily slips into the necked-down part.

If that does'nt work, there's always "JB Weld"-- "The rotorheads favorite Fix-All"! Do what I said, only instead of the lead, roll up a nice ball of JB Weld epoxy paste, and stuff it in there, and put in the stubby.

That will fix your line problem.

Now the choke...I run no choke. It just takes patience. I know it's damn cold up there where you are, so I would give you my "Ya don't need no choke" speech.

But I will say this- If you still have the flap and linkage with the spring on the right side of the choke (looking at the carb as if the primary side is the "front") and you still have the main throttle cable bracket in place in it's entirety, you can hook up your choke cable to the top cable hole on the bracket and link it to the choke shaft linkage arm that should be hanging down.

If there is NOT a giant metal housing bolted to the right end of the choke shaft (Has a thermospring and epoxyed wires) then there's nothing to keep the choke shaft under tension to the linkage.
This means when you pull the linkage arm as if the cable was being pulled out, the flap does'nt move, but now it's loosy-goosy.

A simple twist tie wrapped around the linkage at an obvious place will keep that choke shaft wired to the choke cable linkage.

You will have to hold the choke closed manually, as the automatic choke **** will probably not work. (This is the electromagnet that keeps the choke **** in the out position until the car warms up.)

Then there's a trickier, but important part of the linkage...the fast idle linkage.
The fast idle linkage is a complexly bent wire that is attached to the top of the choke shaft linkage, and likns to a free-moving arm on the primary throttle shaft. When the choke is closed, the wire pulls on the arm on the primary shaft, and the arm cathes another linkage part on the throttle shaft. It opens the primary throttle shaft ever so slightly so as to increase the idle.

Adjustments are made simply by bending parts of the linkage with pliers. Study how it works, and be sure that the appropriate parts line up, and make contact the way it makes sense to you that they should.

DON'T bend stuff if it does'nt make sense to you! You'll be left with useless pieces if it's not done correctly.
As I type this, I must toss in there that you should not be intimidated by any of it. Just do things that make sense, and not *****-nilly. (In other words, None of this:
"Well let's see...I'll bend this and see what happens. Nope. That ain't it. O.K., lemme try this one..."
Think out what you're bending and keep track of what you're doing.

I'm working on a choke set-up just how I described. The carb is spanky clean, and I'll be shooting pics for my website. I can send some to you. Email me.

Trust me- I know...You can get any piece o' **** Nikki to work on your car!

85rotarypower

OK, I will try that then. So the fuel return fitting is not really needed then? I will take a look at it and see what can be done.

Ok just took a look. It can be fixed, I just wasn't sure about the return line and making the choke work. The only thing I don't understand is the linkage to open the primaries a little when you pull the choke. I don't understand why this has to be bent. If I wire the two parts together that you mention, the choke works fine. The primaries open up about a quarter of the way, probably to keep the engine at 3000rpm, but why does the wire have to be bent?

Terrh

iTrader: (7)

it IS damn cold up here, and I'll give you the speech: YOU DON'T NEED NO DAMN CHOKE!



mine don't work, my car starts fine even with its totally #)$(*#$'d carb.

just pump the gas 3 or 4 times before you hit the starter and keep pumping to keep it running for the first 10 or 15 seconds, then it should idle OK...

Sterling

If it's doing the job right (which it sounds like it is) then it does'nt have to be bent.
It's the tab on the throttle shaft that the choke "swing-arm attached to the wire" thing lifts up on that could be tweaked a little side ways either way to adjust how far open the primaries go.
You would do this after the carb is tuned and running, just to ensure that with the choke out, the primaries crack open enough to give 2000-2500 rpms.
(You would'nt want the thing opening the primaries to 4.5K!!!)
That's all that was about.

Sounds to me like it'll work. You won't know till you rebuild it...your next challenge!
(It's not that bad )

Rx7carl

WOw, I missed this whole thread! I'll just add a little info. RB charges what they get for a holley for a couple of reasons. One is yes there are internal mods done on passages and such in the carb to make it run right on a rotary. Two is that all the time/dyno time/track time/ $$$$ spent to R&D this carb has to be made up somehow. So your paying for that as well. Its pretty fair if you ask me, as I bet they put mucho $ into developing the carb.

85rotarypower

OK, Looks like everything is going to work fine, except the accelerator pump. The check ball and weight are gone. I am thinking that when the last person rebuilt it, they lost the weight and check ball. Is there something I can use to substitute for this? I have no idea how big the ball is. This is my first carb rebuild.

Sterling

OK- I just took apart the spray nozzel from a bottle of Simple Green. I'm assumining that all the spray nozzels are about the same (Windex, Fantastic, etc).

Deep iside is a checkball that is the perfect size.

A BB or another checkball...something SMOOTH, small, and heavy will serve as a wieght.

EDIT:
This for under the nozzel set.
The same size ball is behind the AP housing, but the wieght is a very slender, taller wieght.
Hopefully you have that.
If not, then a snipit of copper wire about 1 1/2 the diameter of a #2 pencil lead would work; about 5/16th inch long.
Thing is, the sniped ends would have to be filed dead flat and with no burrs.

85rotarypower

Thanks a lot sterling and everyone else. I think I have the knowledge to get the carb to work. Saved me lots of money.