Hey guys,

I just got a stock '85 12A RX7 which runs like a crap. Doesn't idle very well, has slow or no acceleration, lack of power, oil leaks from the cooler etc. The previous owner didn't care much about the car and told me that the stock NIKKI needs to be rebuilt. Rather then doing this, I found a MIKUNI with 12A intake laying around and was wondering if anyone has done the conversion. Would this be a straight swap? I am looking for a step by step instructions, as I am not an expert on carburetors.

many thanks

 

You'd be better off cleaning up the nikki. It may not be a carb issue at all. You should first verify
that you have clean, adequate fuel flow and pressure all the way to the carb. You may need to
change the fuel filter, replace hoses and/or maybe clean the tank. Hopefully the pump is ok. If it
still runs like crap after doing that, then I would pull the nikki and clean it good or at least run
a bunch of seafaom thru it and spray it good with carb cleaner.

The mikuni will be just as much work since you don't know carbs at all. The learning curve will
be the same and you will still have to do the fuel system stuff anyway.

 

A stock Nikki is gutless and small. A modified Nikki is more powerful than a Mikuni.

 

Not much support for mickunies here that I know of, but as for the factory stock nikki there are some real experts here.

I agree with t_g_farrell you're better off getting the car to run good as is, in a close to stock shape; then move on to other carb choices if you please.


To answer your question "is it strait forward". Yeah after you have a car that can run and idle and everything putting a different carb on is simple. Just re-tune the new carb after installation. BUT if you don't have a good running car like one with fouled plugs, a bad fuel pump, and dirty gasoline it will be the most aggravating swap you'll ever come across.

 

Thank you. Here is more info. The car idles ok if I have the choke ON. With choke off it tends to die. I did manage to adjust the mixture (it was 3 1/2 turns out) to 1 1/2 turns out. It idles slightly better now. Also it idles better with the air filter off and all vacuum hoses disconnected from the air filter. I already replaced the fuel filter, cleaned the sparking plugs, they were black burnt, no improvement. I would like to clean the NIKKI on the car if possible. What is the easiest way to check the fuel flow and pressure?

 

If it idle with the choke and does worse off choke, you probably have a vacuum leak somewhere.
If you pulled hoses off of the carb you would need to pug them or they will be huge vac leaks.

I would take the air cleaner off, and spray the carb really good while running with a good quality
carb cleaner. Then I would run a can of SeaFoam thru the gas tank. You might get lucky and
fix the issue.

To check pressure you will need a guage for fuel and plug it into the fuel line coming into the
carb. To check flow you just need a gallon jug and place the fuel line in it and see how fast
it fills to 1/2 gallon. If it takes a minute or less your probably good to go. The FSM has the
specs on the pressure and fill rate required.

Go here for the online FSM: Foxed.ca