Sunday was a good day - I finally got the new-to-me RX2 running. Sort of. On carb cleaner. The thing hasn't run since at least 1986, but after some rewiring, cleaning, etc. we got the apex seals freed up and the ignition system and starter working, so we pulled off the air cleaner, shot some carb cleaner in, and it fired right up and "idled" at 4000rpm (with a little help from the pedal ).

I have had the gas tank cleaned and recoated (nice work!) and the fuel pump is pumping. After that, it's a mystery to me because I fundementally do not understand how carburators work (I'm a fuel injection guy). The only thing I know is that the return line MAY be blocked with sediment, but that's unclear right now, and probably not all that important since I'm not getting anything useful out of the carb itself...

What is the best way to approach an RX2 carb that's been sitting for 20 years? Should I attempt to rebuild it? Where would I get the kit/parts for it? Should I try swapping some aftermarket carb on there? I have an '82 12A in my garage - can steal its carburator?

On a side note, anyone have any suggestions for something I might be able to run through the fuel system to clean it out? I am okay with replacing the return line if that's what it comes down to, but I'd rather not if I don't. Also, is there somewhere that might sell a blockoff plate for the thermal reactor? I'd like to get that thing outta the engine bay! I can cut one, but I'd rather not reinvent the wheel...

Now, off to read about carbs... Accelerator pumps and jets and floats and bowls... WTF?

 

Well, most RX-2s came with a Hitachi 4-barrel. If you have a very prominent straw sticking into each of your four barrels at a 45-deg angle, it's a Hitachi. I seem to recall that someone found A (read: only one) rebuild kit for it, but don't recall specifics. The first step is to pull the fuel line off the inlet and see if you're getting good flow. If you are, then check the float bowls.

The float bowls act just like your toilet at home, so that when the fuel level drops (as you burn it or stab the throttle real quick), the floats drop a little and crack open a little valve that refills them.

In normal operation, the carb uses the flow of air through the barrels to draw fuel in slowly because of a vacuum it develops (it's not the same vacuum that your intake manifold uses). In order to get the fuel to trickle in consistently, the fuel level has to be real consistent. Too low and it won't trickle, too high and it'll pour in. If you are getting fuel from the lines, check to see if your floats are set too low (they'll shut the valve off before the bowl is full) or if your needle and seat (the valve) is stuck.

Because rebuild kits are hard to come by, be very careful and don't take apart more than you need to yet. Check the fuel, then the bowls. If you screw up the bowl gaskets it's not a big deal, but you'll probably tear important gaskets if you go any further.

Give it a shot and take some pics for us. Oh, and what year is the car?

 

Thanks for the reply... I suppose I understand what a carb does, but I am very visual and it's all hard for me to imagine. I have every repair manual (Autobooks, Haynes, Chilton) ever published for the RX2 thanks to an Amazon.com gift certificate, but all the diagrams in the world don't explain what does what, and they all assume we know how one works already.

Anyway, I thought the car was a '72, but the owner's manual (wow!!!) in the glovebox says it's a '73 and the original title (it's a one-owner car) says it was purchased 6 January 1973. I didn't see a label on the door jamb, and the one under the hood is impossible to read. At any rate, my current best guess is '73...

When you say "straw" are you talking about something running parallel to the length of the barrel, or perpendicular across? I don't have the car accessible at the moment, but I remember something across the barrels at a 45 degree angle.

If rebuild kits are hard to come by, is it worth moving to something else that's easier to service? Another (admittedly lazy) question - is the fuel feed supposed to be the top or the bottom port on the carb? The person who had possession of the car before me apparently "did some work" that may have not been entirely by the book... I haven't found it shown in any of the repair books...

Thanks again...

 

Well, I don't remember which fuel fitting is which, between the supply and return. The "straw" is (I believe) the air bleeds, but It's been a while since I was fluent in Hitachi. The big Hitachi carbs weren't as common as the later Nikkis, though (See pic). It's not a bad carb and is worth fiddling around with for a while. Racing Beat will gladly sell you a new Rotary-modded 4-barrel Holley or you can check ebay, but I wouldn't give up yet. If you have a later Nikki (joint venture of Hitachi and Zenith-Stromberg) you'll find more support for it.

Nearly all carb problems can be solved with some cleaning and adjusting, and you have no reason yet to think it's trash. BTW, the Holley won't bolt straight onto your manifold, but it can be done. If it proves not to be the fuel supply or float bowls, you can always tear into it, clean the internal passages and jets, put it back together with some handmade gaskets, and you might get a good working carb. Besides, you'll learn a lot.

 

Here are pictures of the top of the carb... any help?




It is definitely a 1973....

 

Ah, looks like my old twin dizzy.. my jets were all gummed up.. this is what I did to clean it up a bit. Just put the little strraw on the carb cleaner and spray where i have outlined those read dots.



Hope that helps.

 

Also plug up any vac lines.

 

It does...

Can you also confirm that this is a Hitachi or Nikki carb? I am seriously clueless.

(But if you wanna know about Bosch Jetronic, Motronic, or Ford EEC I can probably help )

 

It's the early Nikki. The 73 and 74 had a slight modification for the automatic choke, but it's nothing major. If you take the top cover off, you'll be able to access all the bleeds and jets indicated in the pic from my last post. You'll also be able to blow out 4 and 5, which are your fuel jets.

The floats are hung from that top cover, so you can check them while you're in there. Have you checked your fuel flow? If so, take the top cover off the carb to blow out all your jets, then hold the cover upside down, hook up the fuel line, and turn the key on. The weight of the floats hanging upside down will keep the needle seated so no fuel should come out. You should then be able to lift each float independently and have a little fuel trickle out of the top cover on each side.

If all your jets are cleared and the floats are opening and closing your needle valve, then it's probably the float height that's the problem (cutting off the fuel flow before the bowls are full), but that would surprise me. Before I chased that, I would unscrew my fuel and air jets (air bleeds) and clean them all really good by hand. All told, yo'uve got 16 jets to clean, so I'd just take a bucket of cleaner or an oil pan with some gas in it, and take them out one at a time, soak in the gasoline, and run a pipe cleaner through them. You can also try real parts cleaner, which comes in a paint can-looking container with a little screen shelf inside. You can dunk your jets in there, let them soak, and they'll clean really easily.

By the way, do everything you can to keep from tearing the gasket. I'd start it by getting an exacto under the gasket, and slowly work it off so that it stays stuck to the cover. If it does separate, then just line it all up, tape it to a sheet of paper, and cut a new one from gasket material at the parts store.

 

Can you really briefly describe what's involved in removing the top cover? I know this is bad, but since the car is not currently at my house I can't actually look at it, and I have to be "precise" when working on it. I'd like to pull that cover off, see about cleaning it up at home, then bringing it back for reinstallation.

Looking at my own picture, is it just a matter of disconnecting the relevant lines and then undoing those four (?) nuts?

The reason for all this is that I am trying to figure out whether it's somewhat mobile on its own or not, because it makes a big difference how I get it up my driveway, which is a serious PITA on a non-driving car... Anything I can get it to do to move under its own power is a huge boon.

Thanks again...

 

Edit: I just reread your post, and it looks like you want to take the carb home with you. If so, then just lose the four nuts, the fuel line, the throttle cable, and the OMP rod (it ups the oil flow per rev when you're on the throttle) and check for any funky vacuum lines. I'm not sure how many there are, but they might run to the manifold, a spacer block, or the carb itself. Check for fuel flow while you're at the car, then bring the carb home if you want to clean it up. Now, on with my original post...



Well, from the manual I see seven screws that need to be removed (go around the outer flange in the black & white photo and you should see them around the edge). You'll want to wiggle it a little as you lift to see if it'll come off on its own. If it won't lift by itself, you'll need to start it.

First things first :

Get gasket material, carb cleaner, exacto knife, and grab a charger for the battery.

Pull the fuel line off the carb, turn on the key, and see if you get decent fuel flow. If you do, then grab the carb cleaner and blow out the four jets that you can access without removing anything, as trainwreck suggested. Blow it out with a can of air, get in the car, turn the key, let the bowls fill, and see if it'll fire. Keep in mind that you might flood the motor in the course of trying all this, so have a plug wrench handy and be respectful of your starter. It'll quit on you if you don't give it a break. If you have a buddy handy, ask him to look down the carb barrels as you pump the throttle to see if you get anything. If you don't, then your needle valve is stuck due to varnish buildup. If you DO have fuel but it won't run, you have clogged air bleeds or your floats aren't set right.

If the easy fix didn't get your fuel moving, you'll need to clean everything. The gasket will overhang the body of the carb by a tiny amount - you should find a little lip of gasket all the way around. Slip the back edge of an exacto knife under and lift from a corner, so that you can slowly separate it. Work it gradually all the way around, lifting the cover the whole time, until it all breaks free and lifts clear. You should now have the top cover with gasket attached. It's up to you if you want to cut a new gasket, but you won't need to if it comes off cleanly.

With the cover off, proceed as above, removing and cleaning all your jets, and lifting the upside-down floats with the key on to see if they're controlling the fuel level like they should. If you've done all this, put it all together, and it still won't start, take a break and tell us where you're at. FYI, another good reference are Sterling and RX7Carl in the 1st-gen section. They've written the book on RX-7 Nikkis and should be familiar with what you've got.

 

That is awesome info, and exactly what I needed... I really need to famliarize myself with the various parts in a carburator and I suppose nothing is better than jumping straight in.

It'll be another week or so before I get to all this (lots of rain, and the car is outside...) but I will revive this thread when I have more information.

The only thing I know at this point is that several weeks ago we pumped fuel from a plastic gas tank through the pump and up to the carb successfully, so I know the pump is working and the fuel lines are clear enough to pass fuel. After that, it's all a mystery.

I also need to look into the return line. I was unable to suck any air throught it while the gas tank was out, so it may be totally blocked. I imagine that will ultimately cause a problem, but I'm gonna work on getting it at least running on its own before worrying about the return system...

Thanks much - I'll report back...

 

Just so you know, the return line is because many old fuel pumps use the fuel flow to cool the pump. Rather than flow what you need, it flows much, much more to keep the pump cool, and runs nearly all of it back to the tank. Just a little ever makes it to the carb. You can run a piece of fuel line from your carb's return fitting straight to your fuel supply if you want to eliminate the return.

The return line, if it IS a problem, won't be your only problem, though. If it were blocked and everything else functioned right, the backpressure would bump the pressure up, overfill your fuel bowls, and fuel would start dumping out your main jets into the throttle bores - all without anything actually running.

 

That all makes sense. I was actually a little surprised to see that return line. The pump on the '2 is the solid-state style, and it's external, so I don't really understand why there would be a return line - there is no bowl in the tank to fill, and I would have imagine the pump would stay cool being outside the car. Guess not!

That aside, I assumed a blocked return line would cause pressure problems up front. Next time I'm out there I do plan on pulling off the fitting at the tank and seeing if any gas is making is back to the tank. Just running the pump, I can hear gas trickling in the tank, and I assume that's coming from the return. If I can't unblock it, I will just rerun it. Not my idea of fun, but whatever... With any luck, maybe some fresh gas in the system will work some of the gunk loose...

 

In that case, then, just make sure you put a cheapo plastic fuel filter with barb slip-on fittings inline just before your carb. If you're gonna start circulating crappy fuel, you don't want to make your clogging any worse.

 

The gas is all-new. The tank has been drained, cleaned, sealed, reinstalled, and refilled with a few gallons of brand new gas. I'll replace the existing fuel filter out back, and once it's all done I'll probably drain the tank one more time, in case nastiness from the lines ends up dumping back there...

 

Alright, man. The weekend has come and gone. Anything new w/ the carb?

 

Unfortunately no... we had a ton of rain this past weekend and I couldn't handle working on the car in the rain... I'm out of town this weekend, but next weekend is locked in!

 

Pretty good news - probably some more questions, too.

We hosed down the carburator with some Berryman's Chemtool and let it sit for a while, then cranked it over. It came to life almost instantly, and we held it at about 4000rpm for a while, then backed off to a pretty steady idle at 800rpm. It seemed a little rough (engine vibrations unbecoming a rotary ) but not bad at all.

I added another 4 gallons of gas (6 total, I think) and poured some Berryman's fuel additive in the tank... WAY too much. It's supposed to be 1oz per gallon, but I added 15oz for 6 gallons. I figured it couldn't hurt, and there was lots of gunk to clean out.

Over the course of the day, we adjusted some things here and there, tensioned some belts, checked the timing, and started it about a dozen times. Sometimes it would crank over and fire immediately, sometimes it needed a little help from carb cleaner. Sometimes it would idle properly, sometimes it wouldn't. But, as it ran more the exhaust got much cleaner and the idle seemed healthier. We had to eventually stop running it as it was getting quite warm, and a bunch of brush and debris that had accumulated around the exhaust was starting to smoke, and we certainly didn't want a fire...

The question that remains:

Sometimes - and only sometimes - when revving the engine there is a loud popping sound that accompanies it. It's definitely RPM dependant, and for lack of a better description it sounds like a helicopter. It sounds like it may just be a massive exhaust leak somewhere in the engine bay, but I'm curious if anyone has any other ideas or suggestions? I'm not familiar enough with what a rotary exhaust leak should sound like...

Next items are going to include nuking the air pump, removing the a/c compressor & related hoses, fixing the exhaust, and redoing the brakes. With any luck, it should be driveable... Maybe a couple more months at the current pace...

 

Check That The Tank Vent Is Open .a Blocked Vent Gives The Same Symptoms

 

Which tank vent? The charcoal cannister vent, or is there another one?

 

yes,that goes back to the tank with a one way valve inbetween.you cuold be running then sputtering etc......i guess that if you got it going now its ok but just chek.