Hey guys, I bought a 1974 RX3 wagon without a motor in it, then took a perfectly running 12a motor out of an '82 RX7, but obviously the wiring harness for the rat's nest was not going to work with a car 8 years older. So after removing the rat's nest, and then stripping down the nikki carburetor, then capping all unnecessary holes, it now idles at about 1,000 rpms, but really stumbles, and there is a bit of a leak coming from the lower carburetor gasket (the 10mm bolts) I made a new gasket and it's still leaking a little. When I push the gas hard it goes just fine, but when I slowly hit the accelerator it stumbles and then almost dies unless you flutter the pedal. When I let the clutch out at idle it starts to move then just dies. It pretty much always dies when the clutch is released unless you get it up past 3k rpms. Also I never noticed before, but when i put the carburetor back on, the choke cable doesn't seem long enough to put the choke back to the neutral position. Does anyone know what the little rod that comes from the front of the engine and attaches to the carburetor does too? No matter how I play with the idle or air set screws, it seems to make no difference. I'm currently in college so I was wondering the most inexpensive way of upgrading the carburetor. Would a 4 barrel holley bolt on? Any help would be appreciated, Sorry I know there's alot of questions, but I want to get this thing on the street. Live in WA state if anyone is nearby.

 

Did it run fine while in the Rx7? if so then its something you screwed with? did you cap all the vacuum ports of with new rubber caps? dont use a screw in the end of a piece of vacuum tube it'll still leak. Check those 3 times before moving on! Personally i would buy a $25 rebuild kit for the carb and at least rebuild the accelerator pump( I've had bad accel pump cause similar symptoms as yours) dont be afraid its very easy to replace it. That rod on the front of your engine is the oil metering pump rod, when you apply throttle the linkage is moving that rod down activating the oil metering pump to supply oil into the carb. Its important to connect it up to the carb. Good luck

 

carb rebuild kit : auto zone has them . also the rubber plugs are a bad idea , they rot because they are all from china and who knows what they are doing to make them last 6 months max .I ether jb liquid weld the holes or use the plastic colored plugs , no leak issue .Holly carbs run great until you turn ,side drafts are a rotary power killer (never seen an intake with a carb do a 180 on any motor ), stay with the nikki , unless you can find a 44idf weber and manifold ,or a dual down draft weber setup .good luck

 

The OMP supplies a metered oil supply directly to the keg via two injector nozzles (not through the carb ), the carb linkage simply operates the volume of oil going through the OMP . You either need to run the omp or start mixing your gas with 2 stroke oil .

There are also different models of holley's that have the float center hung so there is no issues with flooding or lean out during cornering . I would try rebuilding the nikki they are a good carb . maybe if your not up on carbs you should get someone to show you how it;s done help you through the rebuild .For sure you need to deal with the choke problem . Have a good one Gerald m.

 

Mattallac is right, the rubber plugs are garbage but seeing you're a rookie I wouldn't rush into jb welding vacuum ports just yet grasshopper. Use the rubber caps to dial it in and get it running and then look to a permanent solution. I use the colored plastic caps mattallac mentioned and they work great. Take our advice and give the carb a once over and stop screwing with the adjustment screws on the carb. Also holleys make good power but it's true they run dry around corners and you'll get only 5-10mpg. Weber, dellorto etc make great top end but are cold blooded with shitty choke systems if at all. The Nikki was designed by a group of clever little Japanese guys so it's the best option for drivability, power, economy.

 

Gerald m,
This lad has an 82 spec 12A so the oil is sent via plastic tubes to the carb. Keg injection started at 84 GSLSE 13b-on.

 

right noticed the year after posting but make sure the rod is hooked up proper and working . It sounds like it's just hanging there .

 

anyone who can make a holly not starve around a corner I'll send a dollar , 2 people like hollys on rotarys drag racers and people who never had them on there car

 

yeah i wanted to keep it as original as possible and rebuild the carburetor, I just don't want to do it and then have the exact same problems... I'm sure there's a thread on here somewhere about rebuilding the nikki

 

Also the rod is connected but those little plastic tubes broke off at one point or another during the engine install. Where on the carburetor do they attach to? I work at a shop where I could get help with the rebuild but a write up would be nice too. Another issue carb related that could help dial it in a little closer just out of curiosity is that it is a really hard start cold. It takes a lot of cranking and careful placement of the foot on the accelerator. I take apart motors all day but never have to put them back together again... Also they're all piston engines.
Did anyone know about the choke cable thing either?

 

Not much to look at paint job wise but it's rare

 

Don't know much about the nikki It seems to me that they are a poor cold start carb . Once running proper you will need to develop a technique for starting . As far as choke cable goes something must be different for it not to fit , you either need to move the choke mount or replace with a longer good quality choke assembly . good luck Gerald m.

 

nikki carbs are reliable and when tuned right are one of the best carbs for a stock motor , Mazda chose them for a reason .

 

whoa! whoa! whoa! don't go pulling the Nikki apart just yet.

Max Tanner, this was the most important question of the thread (second to yours, i guess) and i don't see where it was answered.

my other issue with the rebuild advice at this stage is the fact that you have confirmed you have a vacuum leak. find it and fix it before you do anything else.

without a functional choke unmodified Nikkis can be quite cold-blooded in climates that get very cold. they are great carbies - very reliable and much easier to troubleshoot than Holleys.

run premix until you get the OMP functional again. if you simply broke the lines, i think i read that there are comparable lines available at Lowe's and Home Depot for you to fabricate/repair your own.

 

I have three, the one that ran fine while on the other car I couldn't get to work again at all. One I had in storage has a gasket leak between the aluminum and metal part with the intake valves, where the 10mm bolts are, tightened it to no avail and i still sucks starting fluid right in and raises the idle like crazy; but that's the one on there now and it idles at 1k RPMs really rough and has all those other issues... I also have a more simple looking one that I found on a farm and took apart with a bees nest in it and all and I'm cleaning that one up in a bucket of gasoline right now because the secondary valves are frozen tight. I ordered a rebuild kit for the farm find one because it doesn't have an altitude sensor or too much extra crap on it. Any tips for getting those secondary valves free again besides dunking in solvent of some sort would be appreciated.

 

well, it sounds like rebuilding the one that you know what's wrong with it may be the best bet.
would be nice if you could expand on this a bit. may just be some detail missed with install/transfer.

 

Well it worked but wouldn't hold any sort of reasonable idle. I just took the original one apart and the upper weird shaped gasket came up without sticking or anything, just came right off, while the lower gasket came off in two pieces, it actually looks better gasket-wise than the one that somewhat works. I was going to use the one that somewhat works as a reference to rebuild the original one...

 

One little thing max . If you are cleaning the carb with gasoline all that it will do is wash the dirt off it won't do any good for varnish etc . that is built up inside the carb . At least get a can or two of carb cleaner and spray the hell out of the inside parts and blow dry with low pressure air ( be careful you don't blow any small pieces away ) . Get yourself a GOOD brake down diagram of the carb so you know what is happening , stuff like that is everywhere on the net. Good luck .

 

the diagram comes with the carb rebuild kit from auto zone