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Very much appreciate the support and learnings we've gained in joining this site, and making sense of our "new" 83 RX-7 that came with a rats nest removal and carb that is in pretty bad shape...
My son and I continue to review much of the documentation referred to us from this forum. As we are working to make sense of it all, and for anyone willing to assist with some silly noob questions, much thanks in advance for any advice on the following:
We've taken the carb apart to the point where we have all the ancilary items removed (what was left standing from the rats nest removal, that is), and have the main carb bodies seperated. There is considerable corrosion in the float bowls as seen in the image below. Our next planned step is to clean thouroghly using our ultrasonic cleaner (simple green pro hd, 3:1 ratio). Here's our noob questions:
For the upper body, I've read not to touch the float needles. Should I simply not place the upper body into the cleaner? I am worried about the amount of debris from the corrosion we found in the float bowls, and how that may have impacted the needle valves. Recommendations on how we might address?
Although the car is an '83, the carb on it looks to be an '84 and has the altitude compensator. Once removed, the gasket looks as though it has been sealed in place. I do not see a replacement gasket in the rebuild kit. If you were us, would you simply keep in place and not clean the upper body?
Thanks for any thoughts / recommendations.
Last edited by C&K; Oct 13, 2025 at 06:53 PM.
Reason: Answered some initial questions on our own.
We are making good progress, and have decided to simply take everything apart and clean extensively. A lot of surprises - I'm floored this carb ran at all. One surprise we found has me baffled. Picture below are the needle seats, where when we disassembled, we found some form of plastic thing on one of them... Does anyone have any idea as to what this is?
There are filters all over that carb that are not really needed if you have a decent fuel filter after the pump already. They are, as you found out, under the seats and also at the fuel line inlets if I remember right as well. These will all cause strange issues as they get old, deteriorate, and collect gunk. When I hogged out my nikki I didn't put them back in. Your approach is sound, remove every piece and then sonic clean the non plastic parts. Also, blow compressed air through all the passages as they come out of t he cleaner. You will be surprised and what pops out.
It has been pretty amazing the amount of crud we've been able to get out of this carb, that's for sure. And as one would assume, we're certainly not the first ones to rebuild this unit. It looks like we do not have any of the weights for the check ***** anylonger. Someone had actually placed two ball berrings under the AP nozzle, I guess to use one as a weight? Nothing was in the AP inlet at all... Would you simply replace each with the new, single check ball? Or is there somewhere I can source replacement weights?
It has been pretty amazing the amount of crud we've been able to get out of this carb, that's for sure. And as one would assume, we're certainly not the first ones to rebuild this unit. It looks like we do not have any of the weights for the check ***** anylonger. Someone had actually placed two ball berrings under the AP nozzle, I guess to use one as a weight? Nothing was in the AP inlet at all... Would you simply replace each with the new, single check ball? Or is there somewhere I can source replacement weights?
You would have to source some used carbs to use as donors I think. Unless someone can measure them exactly and weigh them so you get the exact right size and weight.
It has been pretty amazing the amount of crud we've been able to get out of this carb, that's for sure. And as one would assume, we're certainly not the first ones to rebuild this unit. It looks like we do not have any of the weights for the check ***** anylonger. Someone had actually placed two ball berrings under the AP nozzle, I guess to use one as a weight? Nothing was in the AP inlet at all... Would you simply replace each with the new, single check ball? Or is there somewhere I can source replacement weights?
The exact weights themselves shouldn't be too critical. While the factory weights are surely designed to a particular spec, the most important part is just having a weight to ensure the check-valve function of the ***** works consistently. Realistically as long as whatever you use for the weights is relatively inert (brass or corrosion resistant steel), won't get jammed, and allows fuel to flow around it they will function adequately. You definitely want something in there though, I wouldn't just leave it with a single ball. The two ball bearings honestly isn't the worst idea if the factory weights are MIA.
The exact weights themselves shouldn't be too critical. While the factory weights are surely designed to a particular spec, the most important part is just having a weight to ensure the check-valve function of the ***** works consistently. Realistically as long as whatever you use for the weights is relatively inert (brass or corrosion resistant steel), won't get jammed, and allows fuel to flow around it they will function adequately. You definitely want something in there though, I wouldn't just leave it with a single ball. The two ball bearings honestly isn't the worst idea if the factory weights are MIA.
This is a good observation and probably true. Plus you could use multiple ***** to adjust if needed for the weight.
You can use the needles and seats found in the rebuild kit if you put a lot of time into chamfering and smoothing out the raw machined parts. It's an absolute last resort only if you can't salvage the stock needles and seats.
As for the altitude compensator gasket, some regular parts store gasket paper would do the job.
I've got a few spare carburetors. If you list out what you think you're missing, I should be able to spare some check *****, weights, and others.
Really appreciate the advice and thanks for the offer Ta-Aikah! We were able to source the missing weights as well as a throttle adjust screw which we realized was also gone. All said, we've completed the rebuild.
Aside making sense of the rats nest removal, what was left standing, and learning how to get the carb put together correctly, we are now working to hook everything up in our atttempt to get the best running condition possible. More surprises and more questions - I'm sure we will have many more new threads we can entertain here...
Some final questions first though as we reattach the carb with fingers crossed:
Looks like we have a "ported" intake manifold. No idea what good vs bad should look like, but this seems pretty well butchered. Much thanks to @TimWilbers in helping us ID the coasting valve. As you can see in the pic below, it looks like part of the porting included a rough removal of the shutter valve. It feels like we will have some vacuum leak here as what was left standing is pretty loose. Any recommendations on a best way to resolve?
Our carb has the altitude compensator with three lines coming from it. Two on top (one with a 90 degree bend), and one on the side. As it came to us, the 90 degree bend line was uncapped - the other two were capped off. After reading some conflicting information, we're unsure how to handle. Confirming that the 90 degree bend is the #2 MAB or a vent for the compensator, thus keep it uncapped? Cap the other two?
The vac advance pots on the dist were both simply connected to each other. I've read that there should be a tee in place connecting both of them to the second from the left vac port on the base plate. I've also read that this is true for the primary only - that due to the emissions delete, to cap off the secondary without the control valves of the rats nest and just connecting to the manifold, that it could retard timing under the wrong conditions, cause hesitation or poor idle... Any advice here as to what is accurate and best practice in our situation?
It has been pretty amazing the amount of crud we've been able to get out of this carb, that's for sure. And as one would assume, we're certainly not the first ones to rebuild this unit. It looks like we do not have any of the weights for the check ***** anylonger. Someone had actually placed two ball berrings under the AP nozzle, I guess to use one as a weight? Nothing was in the AP inlet at all... Would you simply replace each with the new, single check ball? Or is there somewhere I can source replacement weights?
First image (ref Mazda Carburetor Manual):
Top pieces are parts # 93 and 94, with a weight that came out but does not have a part number
Middle pieces are parts # 73, 74, and 75 for the accelerator pump
Bottom is an unknown weight that is in the wrong bag
Second image is the gasket for the altitude compensator. You will not find it in a carb rebuild kit because it is included in th engine rebuild kit (?????).
I bought 2 kits in 2014 (long story). I used one of the gaskets for my carb rebuild earlier this year and have no use for the other one.
If you want this stuff, send me PM with a mailing address. No charge.
Thats kind of a hack job on the intake modification to channel the primaries to secondaries. The problem I see with it is there may be flow differences between front and rear rotors. Not much left to get them evened out. I'd probably go with it for now and get another intake to modify better.
Mine look like this, not perfect but reasonably symmetric.
We are close... Carb reinstalled. Started the tuning process only to pause as the main nozzles are dripping gas for a bit following turning the key off. There is an aftermarket fuel pump on the car, so we are going to test pressure first to see if this is the cause. If that's in spec, we will look at the float levels again... Unless anyone has other ideas? We'll take them
Altitude Compensator: We still can't make sense of it with all the emissions having been yanked. For now we have the 90 degree bent line uncapped (atmospheric vent?). We believe the vertical line next to that was for the vacuum signal for AC? Capping that. Horizontal line on the top - no idea... Is this a bowl / air vent? Image below; any thoughts/advice/opinions appreciated. Red arrow = capped. Green = open. Yellow = ??...
Vacuum advance pots: From what we've been able to understand: Front pot is ignition advance - connecting this back to the second from the left vac port on the base plate. Rear pot is retard / altitude control? Without emissions now, we're capping it. Again, any firm knowledge, thoughs/opionions/etc greatly appreciated.
If you mean the vacuum advance pods on the dizzy, one is for leading and the other is for trailing. If no rats nest just hook them both the the second nipple from the front on the nikki base plate which gives you ported vacuum (no vacuum at idle basically).
Back at it with some time off for the holidays. We believe the previous owner did a partial carb rebuid (i.e. replacing parts, but not truly full disassembly and cleaning), which included using the new needles and seats. We are assuming this to be the cause of our main nozzles dripping fuel. We don't have the originals thus are stuck trying to make these - or the new ones we have from our own rebuild kit - work.
@Ta-Aikah you mentioned ealier in this thread spending a lot of time chamfering and smoothing out new seats to make a good seal. Do you or anyone else in the forum have experience / advice you could share on how to best accomplish? I've purchased some simichrome polishing paste. Our current plan is to use a little paste to polish out the inner portion of the seat, then bench test with low air pressure until we find the needles seating properly....
I don't have experience with it personally, but the idea is to make sure there aren't any burrs left on all of the surfaces you can get to. Honestly, a Scotch-Brite scouring pad (probably green) is likely your best bet.
I like the idea of lapping the seat like a valve. That won't hurt, but is likely not causing the sticking.
If the sticking needle and seat are causing your overflowing main jet, it's probably a burr/edge on the four main edges of the needle catching on a burr on the cross-drilled holes in the seat. Does that make sense?
I've done this by using compressed air with the top off and holding it upside down and bouncing the floats up and down a lot to get it to move smoothly. Just don't go nuts with the pressure.
