hunterkai365

Aloha, im new to the forum, this is my first post so i hope im doing this correctly, i apologize if not. Ive read alot and tried to just solve my problems that way but im stumped.

i have a 1985 mazda rx7 gsl (12a) manual transmission. As far as i can tell its got a stock nikki carb, and looks to be an 85 as well. I bought it 2 years ago and it barely idled, backfired alot, blew white smoke, reeked of gas, and would stall when you pressed on the accelerator hard at low rpm. Seller told me it just needed a carb clean, possibly rebuild and she’d be fine, so i bought it, actually drove it home(kept it revved up)

after sitting for 6 months I decided to finally do some work to it. Ran through all the vacuum lines and made sure they were hooked up correctly (more than a few of them weren’t) after fixing that it seemed to at least idle. Then i drained the old gas out, put in ethanol free, changed the fuel filter, spark plugs, oil, and oil filter ( i live in hawaii so i put 20w50 in per mazda service manual) I also messed with the timing a bit, it appeared to be super advanced so i had to retard it a bit. On top of all that I sprayed a crazy amount of carb cleaner into the carb. It still has all the same problems but it can idle. It seems to idle super low when its cold, like 1k or less, then when it warms up it idles like 2k.

so I decided to just pull the carb and rebuild it, im in the middle of rebuilding it right now, and it seems super clean, all the gaskets look pretty good condition, almost new. Can anyone help me figure out what might be the problem. I thought the accelerator pump might be the culprit but it looked to be good condition.


id also really appreciate any links to some useful threads with similar issues to me or threads on rebuilding the nikki carb

mahalo

diabolical1

iTrader: (3)

may have been maladjusted floats or the needles/seats (in addition to whatever other tom-foolery had been going on with the car) ... but none of that matters now.

you're in the middle of a rebuild, so here are some resources that might be helpful.

hunterkai365

Measured the distance between the floats and the airhorn, looks to be in spec. I see this valve thing, i think it’s the dashpot delay valve, not too sure tho. Im not able to blow through it either direction so that’s concerning. What is it and should air be able to pass through in a certain direction? Referring to the green thing in line w the hose

hunterkai365

diabolical1

iTrader: (3)

it's some sort of check valve. for what, specifically? i'm not sure. i will have to look it up or wait for one of the more adept Nikki-masters to chime in.

you mentioned blowing, but ... *pause*... did you try sucking? more than likely it would be exposed to vacuum.

diabolical1

iTrader: (3)

found this while searching for an answer about the valve. thought it might when you get the Nikki back together and need troubleshoot:
https://www.rx7club.com/1st-generati...-carb-1126137/

here is an annotated diagram for future reference, but it does not show the valve: https://www.rx7club.com/1st-generati...i-carb-912089/

maybe take photo of what it attaches to on the other end of the hose?

hunterkai365

Didn’t try sucking, wouldn’t that do the same as blowing from the opposite end


heres a pic of where the other end of the hose connects to. Not sure what it is because my haynes manual, which is for my year, is for a different carb than mine, I think they used an earlier model for their teardown and grouped it all together in the same gen.

KansasCityREPU

iTrader: (9)

Blowing in the opposite end may not work if there is a check valve only letting air flow in one direction.

hunterkai365

I’ve been using this site for a while, it’s really helped me a lot, but the picture quality isn’t great. Also i see the check valve in the diagrams but it’s not labeled. Ill link it so you can take a peek.

1985 Mazda RX-7 Factory Service Manual

hunterkai365

Figured out my problem, probably didn’t need to rebuild my carb but I’m sure it helped. Turns out I had a vacuum leak. All my hoses were properly connected but there was a hole melted in the hose that connects the intake manifold to the anti afterburner valve, also known as the Mystery hose. To think I was stumped for over a year, ready to throw in the towel. Hearing her idle at 1k was such a great feeling.

diabolical1

iTrader: (3)

i'm sure you are neither the first, nor the last .... what matters is you stuck with it. sometimes these cars (or just cars in general) can be about small victories.

i think vacuum leaks cause many people to run around in circles because they can manifest in different ways (low idle, high idle, rough idle, or no idle). there are so many places they can happen that they can be very hard to locate. nevertheless, if you don't find it, then you can go off in another direction possibly making your life more miserable.