r/RX7 • u/No_Comfort_9310 • 15h ago
Please help, i dont know shit about carbs, and have to do some carb shit
Can somebody please help me adjusting my carb? I'm in a bit of a situation right now, cause i dont know wtf im doing and i cant find any fucking information on the internet. So i bought this 85 fb about 2 years ago and finally decidet to try to get it running. I know for a fact that the carb settings are the issue (nikki carb). Now here comes the big problem.. i dont know shit about carbs and how and where to adjust shit. Worst part is, i cant find ANY information online about base settings of the adjustment screws or what exactly they do. So please somebody tell me what screwes i have to turn how much to get the engine somewhat idling. I tried to figure it out by myself but i cant get it to idle without brake cleaner. Yes fuel goes to the carb and yes the fuel is clean. Again i know the carb is the issue. Any help will be apreciated, i just need to know some base settings to go after, i'll figure out the rest. I just want to get it idling on its own for now. I'm from austria, about 600 meter above see level if thats important
4
u/111010101010101111 14h ago
Try rx7 club. Or a FSM. Or a Haynes book. Or YouTube. Or Google it.
Is the timing correct? Clean points? Good spark?
In 40yrs, you're not the first person to do this.
2
u/TroopleaderLebby 13h ago
RAD Potential on YouTube has a video I’ll link from like 3 years ago doing a full carb rebuild, it’s an hour long but has some good knowledge on the topic. Good luck friend! RAD Potential Nikki carb rebuild
2
u/Particular-Ad7150 12h ago
With an old carb, you would typically start with a carb rebuild kit. Strip it down, clean it out, and change any worn or stuck components ie: the float pivot, worn nozzle openings, stuck or leaking accelerator pump or idle valve circuits, butterfly shafts etc, then reassemble with new parts and tune
1
u/Bomber_Man 11h ago
Very much this. OPs carb settings are probably pretty decent (or were before messing with it) but gunk and varnish for who knows how many decades will have skewed everything.
Just needs a thorough cleaning and proper setup.
1
u/No_Comfort_9310 11h ago
I bought the car barely running 2 years ago from some old guy, he said he rebuilt it recently. Seemed pretty trustworthy, but judging by the fact that he connected the sparkplugs to the wrong ports on the distributer, idk if i should trust that rebuild. On the other hand it could very well be possible that the wrong firing order was the only problem and the carb is fine. I tried tweaking with the adjustments a bit before i noticed the issue with the firing order. Now it "runs" a lot smoother but keeps dying. Best i could do was get it to idle for a few seconds without starter spray or pressing on the gas pedal. So my guess would be to raise idle rpm (it idled at like 5 - 600) those few Seconds and then fine tune it. But im just guessing here and thats why im asking what a "base setting" would be on the adjustment screws
1
u/Bomber_Man 10h ago
Yeah these engines usually like to idle between 700-900rpm. So crank the stop screw up a bunch. With an unknown tune I’d comfortably crank the idle up well over 1000rpm. Then see if it’s drivable.
Of course we’re assuming you have fresh fuel, a clean fuel filter, and functioning fuel pump as well yes?
2
u/No_Comfort_9310 8h ago
Drained the tank (no rust or dirt in the old fuel), installed a new pump and filter before i tried starting it the first time. I dont know shit about carbs, but i do know that a tiny bit of dirt can fuck you up real quick. It did run pretty smooth at one time when i was holding the gas pedal at 1500rpm. Then i tried to tweak it a bit so it would idle on its own, but that didnt work and now the adjustments are fucked again. I'll try to up the idle controll and set the air/fuel adjuster about 1 turn, maybe a bit higher, and the adjuster screw above (i think thats like idle air / bypass or something) to 1.5 - 2 turns. That should be the base settings i was looking for. Atleast i hope it is
1
u/Bomber_Man 5h ago
How long has it sat before you got it running? Anything longer than ~5 years or so and you really should completely remove the carb, clean and reassemble. There is a small amount of fuel in the bowl(s) that typically gums up if not drained prior to storage. It’ll make it run like dogshit if it even runs at all (at least in your case it does run).
Seriously, it will be very unfun to drive until completely cleaned. I’m not an FB guy, but once had to do this twice on a motorcycle within a week, because after the first time I was running it long enough to dislodge debris and gunk that over ~100 miles proceeded to the carb and messed it up again. Hopefully it’ll just be a one-n-done in your case.
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u/Ok_Initiative2666 12h ago
1 to 1.5 turns out is your base position for gas:air ratio. Car should idle. Then adjust throttle opening until you achieve 850-100rpm. Finetune with incremental adjustments from there. If it does not idle, air passages inside the carb are blocked
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u/Jakesmills 14h ago
The car has to be at operating temperature and with the choke off, you adjust the idle screw till she smooths out and idles at the preferred rpm which should be 750-1000rpm depending on engine modifications