Hey all im pretty new here, mostly troll around trying to learn about my 84 gs. Here for the last month if I ride in say 4th gear at around 2200 rpms the car will randomly start to "sputter" like its suffocating. The problem occurs in every gear but only after I pass 2k..... but i can drive around under 2k and it runs perfecly fine. Im sure its a problem with my carb and my mechanic said it could be the vaccumm diaphram? So would I be better off trying to rebuild the carb or try and find a "new" one? Any suggesstions are greatly appreciated.

 

Replace the fuel filter. If that does not do it - check for blocked exhaust.

You are better off to rebuild your carb than to buy a autozone/checker rebuild. As long as it has not been hacked up by someone not knowing what they were doing or it is clogged so bad that can not be cleaned or corroded the Nikki is pretty bullet proof. New are NLA.

Have one here now, 83, was running out of fuel, they replaced fuel pumps, overhauled carb, flushed the tank charged the guy a bunch. Had an aftermarket fuel filter in it, I replaced it with a Mazda factory filter and now it has pressure all the time and runs great. Had to scrap off a non-mazda gasket off the carb, all the vent ports were blocked, and now besides running great it passes emissions 0 HC 0 CO,( 1600HC 18%CO when it came in)

120,000 miles. All original.

 

Yeah I probably will end up rebuilding it, im reading through sterlings website now lol. I should have mentioned earlier what all i have done to the car since ive had it just to get where I am. I have cleaned the fuel tank, replaced the fuel pump and filter (filter several times), replaced alternator, dist. cap, rotor button, plugs, had the doughnut replaced on the exhaust, and a few other to try to get it running better lol. Whould it be risky to try and use parts from a carb off a 1st gen at a junk yard?

edit.... also forgot to mention that for the first month or so of having the car this problem did not occur.... not sure if that helps any lol

 

I do not think it is a carb issue right now. I have had fuel tank pickups bad from rust, even after tank cleaning. But if it will not go over 2K, check for blocked exhaust, pull cats. Precats have a tendency to loose the mesh that holds the substraight in, it blows back to the main cat and blocks it. I have seen main cats go and the mesh went back into the muffler and blocked it there.

 

I will definately check the exhaust out next. But the car will rev over 2k if I pump the throttle no problem its just that cruising down the road theres no tellin when it will die on me once I exceed 2k. another question.... what can cause the tachometer to stop working???

 

Trailing ignitor.

 

If you've had to replace the fuel filter frequently due to plugging from rust, it's time to drop the tank, have it boiled and resealed. The pedal pumping indicates it's a fuel flow/pressure/supply issue. All you're doing is adding fuel via the accelerator pump, stealing fuel from the rear fuel bowl which may starve the rear rotor.

 

make sure the fuel reducer befor the carb is in the right way and not blocked.

 

The 'fuel reducer' is a one way valve that's installed post carb, not pre.

 

Check your vaccum hoses, sounds like it might be a leak...

 

thanks for catching that.
I have had build up come from the carb and jam that valve.

 

Up to 2000 rpms the fuel is primarily supplied by the idle circuit. After that your primary fuel jets kick in. Take the top of the air cleaner assembly off and see if you see fuel spray out of the emulsion system on the primary barrels as you slowly move the throttle shaft "dont confuse the emulsion tubes with the outlet tubes for the accelerator pump". If you don't see fuel coming out and it studders and dies then you fuel jets and emulsion tubes are probably restricted. I doubt you have a vacuum leak because you said it idles well.

 

i would first remove and rebuild the carb. it sounds to me like your jets are partially clogged. after rebuilding or during, replace the fuel filter and drain teh tank and check for sediment. you can even remove it at that point and check the pickup screen for blockage. once the pickup is out you can check for sediment inside of the tank. i have a writeup with pics on dropping the tank. if you like i can post it here.

 

thanks for all the suggestions guys. ive been very busy and just got back in town for the holidays and can finally work on the car some more. Today i started her up, let it warm up, sprayed some carb cleaner, and let it idle for a short while. i then drove a few laps around the block and the car died on averaged once per block. it seems that the carb cleaner loosened some gunk up possible but im not sure. is there anything else regarding that that i can do? im a bit hesitant about messing with the carb cuz i reallllly dont wanna make anything worse but any suggestions are welcome. oh and with the intake off and after sprayin some cleaner i was able to revv to redline with no bogging down.

 

Check your ignition, and make sure you have spark on all of the plugs. With the loss of the tachometer, this is sounding more like an ignition issue than a carb thing...






.

 

Time to learn carbs, I think... sounds like an internal clog or a gummed up screen.

Take off your air cleaner, and watich your float bowl levels while you raise the RPMs by hand. IF they drop significantly, you have a clog before the floats. If they don't drop but you still stall, odds are a clog in the mains somewhere.

 

sorry bout the confusion with the tach.... my brother has an 85 and it turns out he had a bad sensor causing that problem lol. I just purchased a haynes so im gonna study a bit

 

Switch the ignitor leads on the distributor and see if that works and let us know.