Hi guys, been awhile since I've had a chance to hop on the site and post anything about my 83. Got married and had twins, had to get another car that actually had a backseat . But anyway, kept the ole girl and have recently dusted her off and yup still purred like a kitten. Well now that I have a daily driver and things have settled down at the house I have the time to give her some much needed tlc.

I'm going to start with the carb, I have a modified Nikki from a guy I can't get a hold of anymore. The problem is when I put it on (this was a couple years ago) it would start and die at idle, if I kept bliping the throttle I could keep it running otherwise it would die. Now I haven't put it on again since so I'm going to throw it on this teusday so I can confirm my memory and get more details. A little about the carb... It's stripped down, the secondaries are bored out, venturi arms smoothed and knife edged, acc pump has been messed with but not sure what. I'll post some pics up and measurements when I get em. The question is is there a possibility the pieces on the carb are mismatched? Or is it more likely a transition circuit or idle circuit issue?

 

On primary side I've got
70
40 might say 46
180

Secondary
60
140

Can't tell if they have been drilled or not but arnt those stock sizes if undrilled?

 

I hate to say it but your carb is another victim of that CobraStngSVT guy. Everything that can be done wrong to a carb, was done wrong to it because that guy didn't know what he was doing.

Your carb will never run right. How do I know this? Because I worked on an identically modified carb by the same SVT guy about two months ago for Jinkun. I got it working for him after undoing everything that was done wrong and redid it all the way I do carbs and even tested it with boost successfully! And it worked! But only after spending far longer on it than I had planned.

For better or for worse, at least now I know how long one of these so called "SR" Nikkis takes to fix. I am willing to take on another one if you're willing to allow me to do so. Pay shipping both ways and maybe a little for my time to fix the venturis and to order some correctly sized jets and maybe a new rebuild kit if it's needed.

No, this is not a business for me. Just a small hobby. I've gotten pretty good at it, too. If you follow any of my hogged out boost prep threads where I lay it all out there for all to see, I have no secrets because secrets don't help anyone. You might call my approach "open source". Like a GNU carb. That sounds weird. Oh well, I said it first.

Ok to address your specific questions,

The reason why the SR Nikki will start and die at idle is because his venturi cut is grossly inefficient and will never work. It's due to the way it was cut. The narrowest part is supposed to be right in line with the bottom of the booster but this guy cut it from the top which moved it 9mm below the bottom of the booster. That's right! If you don't believe me, just look down into the carb to see what I'm talking about. The only fix it to pull these pieces of trash and install properly cut ones. I might still have one set of pristine stock ones I could hog out properly and install. Maybe. I'll have to look. I hope I do.

Both your primaries and secondaries were bored out by his lathe. On Jinkun's carb, I could see a variance in his machine which left a nasty edge inside. That's so sad. lol

The so called knife edge wasn't performed on Jinkun's carb so I doubt it was performed on yours. The SVT guy only took a dremel and attempted to smooth things which was a waste of time because air doesn't flow around those areas where he spent most of his effort. Lame mod. The way I do it is like Sterling where I actually knife edge the support arms. I call it the airfoil mod or the aerofoil mod depending on my mood.

The accel pump diaphram area doesn't look like anything was done to it, other than shoddy powdercoat (which should never be applied to a carb). However I know he does drill out the banjo bolt and nozzle WAY TOO BIG which ruins them. I have a spare nozzle and banjo bolt to provide, drilled properly of course. I can also do the Sterling mod to the diaphram area. But there is still a problem due to the media blasted main body the idiot SVT guy would do. It produces millions of micro craters. These allow the fuel to leak down past the checkball which causes a random accel pump glitch. Basically sometimes when you step on it, no gas squirts out. It happens randomly and should clear up on its own after some break it time. See, the little ball bearing or rather checkball is hard steel while the carb main body is soft, like zinc I think. Constant use should polish the metal and make it work again. I have no idea how many miles this will take.

Something else I noticed about Jinkun's carb once it ran well enough that it could be driven for the first time. These carbs, like Sterlings and Yaws, all have a crappy Holley dominator air bleeds used as fuel jets in a misguided attempt to have tunable jets. The problem I discovered is Jinkun's carb had a strange cornering issue that I've never experienced from any other Nikki before. It reminded me of the stories about Sterling carbs having cornering issues and he was working on some kind of baffle that could be install in the float bowls. Yaw had worked on something similar, apparently. You want to know the actual reason why I think Jinkun's carb was having cornering issues? It was due to the inefficient shape of the funnel in the Holley air bleeds. To see what I'm talking about, all you have to do is visually compare the funnel shape of any stock Nikki jet against the Holley and you'll see what I'm talking about. Since then, I discovered a website that sells Hitachi jets which the same design as Nikki jets and come in a variety of sizes every .2mm so it makes fine tuning a breeze. This is how it should have been for us in the beginning. But I only discovered these a couple weeks ago. Search for jetsrus.com on your internet search engine.

All the air bleeds you can see, and the numbers you provided, are stock. I don't think the SVT guy drilled them out, but then again anything is possible with this guy. I don't trust his work further than I could throw one of his SR Nikkis.

If you want this carb to work, you need to seriously consider having it corrected by someone who is competent. I know you already spent some money on this boat anchor but you aren't the only one who was duped by this guy, so don't feel bad.

By the way, there was media everywhere inside Jinkun's carb. That SVT guy didn't even clean his mess up properly. I'm sure your carb has plenty of media lurking here and there that will free up and go into your engine at some point.

 

Here is the thread detailing Jingkun's carb. It has pictures of the shoddy powdercoating and plenty text to read. The thread transitions from speculation to hard core facts after he sent it to me and I got busy correcting everything. Enjoy! https://www.rx7club.com/1st-generati...tions-1064548/

 

I just studied the three pictures you posted. Um, where's your fuel rail? It's kind of important. I have no spares.

All the drilled holes in your air bleeds appear stock, thankfully. The primary short slows are still too big though. They are too big from the factory and need to be smaller to work without a choke and especially with hogged out venturis. But I don't blame most people for not knowing this. It's not commonly known. Sterling only barely touched on it and Yaw didn't do anything with them.

I also notice your return spring bracket doesn't look stock. The non-stock angle and length add up to a pedal that won't be quite stock feeling. good luck with that. Was it an SVT mod or something you did? If it was an SVT mod, I don't understand the point of it. Then again, nothing that guy did was any good.

I also couldn't help noticing the cable linkage has been monkeyed with by the SVT guy, same as Jingkun's carb. I had to get in there and redo it with some stock spacers and other hardware to get the cable lever to align with the cable bracket so the cable wouldn't be at a funny angle which leads to premature cable wear and a stiffer pedal that doesn't return to idle fast enough. Makes me wonder about the angle of your return spring too.

Man, if only I would have known as much as I do about Nikkis back in the day, we could have laughed this guy off the forum before he had a chance to ruin so many carbs.

Hmm, I wonder how many more are still out there? Two down, ten to go? Did he mod that many?

 

Correction: Oh I see why the the return spring bracket was modified. It was to allow the spring to stay in place while the top is removed for easier tuning. Sterling did something like that as well.

Well guess what. I've had the tops off of various carbs hundreds of times and I never once felt the need to redesign the stock bracket. Why? Because the stock setup works great and, while it is one extra step why taking the top off, it is not a big deal. I've also found that once the basics are figure out, the tune is repeatable across several carbs.

Example: Jingkun's carb received my best guess turbo tune and it turned out to be perfect from the very first test drive! There was no need to constantly take the top off to change an air bleed or a fuel jet. Kind of rendered the modified primary air bleeds moot as keeping them at 70 is all you have to do for these carbs to run right. There is zero need to mod them! Oh well, some people think stock sucks and will do everything in their power to leave their mark. Sometimes that's great but most of the time it's by someone who has something to prove (the SVT guy with a Mustang based name on a rotary forum) and it usually ends badly.

Well, I've typed enough for now. Hopefully you got something useful out of all this and will make some informed decisions about your poorly modified carb.

 

Thank you Jeff20b for confirming what I was afraid of . I've been back on the site for a few days now and have read thru most of your posts on nikkis and have already checked out jetsrus. And yeah boosters not knife edges like I thought they were, wish I had just kept my money. Would it be cool if I picked your brain sometime, wanna get it tore down and think about what I want from the ole 83, might just go with a turbo build instead of NA since I'm not auto-Xing her anymore. And the fuel rail is on my other stripped stock nikki, I have AN fittings on my fuel lines and that one had them on there.

 

Ok, gotcha on the AN fitting. I know the SVT guy offered that service.

Yeah, I can provide the info you need. From reading through Jingkun's thread and this one, plus anything else I can tell you, you should be able to get that carb working. You will, however, need to come up with a spare set of venturis and hog them out the correct way if you want to make more power than a stock carb is capable of. And yes, boost prepping is worth while because these carbs love boost if you do it right.

 

Thank you Jeff20B, I'll pull that anchor apart and put some eyes on it and take some better pics. Is my only option for venturis going to be getting another carb and pulling them out? If so would it be best to just scrap this thing (by finding him hand delivering it back thru his window?

 

Basically, yes, and yes.

I was able to save Jingkun's carb only because I had a spare set of venturis from a dead carb I tore down a year before.

Hmm, maybe offer this carb up for sale on the forum rather than throwing it through said jackass' window. Maybe someone out there has a set of spare venturis and has masochistic tendencies in order to want to take on such a painful proposition as a ruined carb that may yet work again. It all depends on how motivated you are to make it work again, I suppose.

 

Oh well, I am gonna hunker down and fix this headache. It's not like it's my only carb or only car, so I don't have to rush anything and I just take my time and mod this thing the right way. The threads I've been reading thru of yours are super informative, feels like I'm getting a grasp of tuning the Nikki but just a grasp. I have alot of reading ahead of me and searching through the forum, kinda bringing back memories of when I first got the Rx7 and knew nothing at all about them. Just need to stop thinking about getting ripped off so I can have fun and enjoy the learning process. Thanks again Jeff20B, looking forward to getting this carb in a useable condition..... Challenge accepted svt douche!

 

What I find most interesting is the SVT guy does not come on here and defend himself in any way.

I agree with the "with a Mustang based name on a rotary forum" sentiment as well. I mean
think about it, would you hand your carb to someone who is obviously not primarily into rotaries.

 

I think it's because too many people want their money back. The guy failed to deliver a carb that actually works, and he knows it. He has good reason to stay away.

I, for one, don't want him back here, stinking up the forum. Good riddance.

Edit: Thinking about this touchy subject a bit more, I think I understand why I'm feeling this way. I've just spent the better part of a year, beginning last Feb, working on these carbs, modifying them, making them work with boost in a better way than anyone ever has before, and finding that with each breakthrough, my level of respect goes up for all the excellent engineering that originally went into these carbs, and for Hitachi (the parent company), Nikki (the factory/plant that builds these and makes them work on rotaries), and Mazda for using these high quality carbs, and lastly everyone who uses these carbs and doesn't go off into fail injection land. I would never do anything to ruin a Nikki and I think everyone here would concur. So when I see the level of shameless self promotion from the SVT guy compared with his actual incompetent "work" if you want can call it that (I'd call it butchering or hamfisted to be polite), and how he charged people $400 for carbs that didn't work while riding on Sterling's coat tails, I can't keep quiet about it. I have to expose every obvious glaring mistake because facts don't lie. Jingkun's carb's baseplate was so rusty it would never idle. This proves the SVT guy didn't even bother test running at least this one carb before he sent it out the door. What does that tell you? It wasn't even the same carb Jingkun sent him.

So even if this SVT guy comes back and makes an attempt at defending himself and his shoddy work, what good would it do? The truth is out there. Here, on the forum. I've said everything I needed to say. And I didn't even give the guy any money. I've got no dog in this fight, as they say. All I can offer is a warning, which I've done. If I was him, I'd be more worried about all the people he owes money. I can see why he hasn't been back.

 

I sent SVTMoron a set of venturis to modify for me, throttle shafts, and emlusion tubes/air bleeds. I think he charged me $100. The shafts and air bleeds were so bad that they couldn't even be installed. I could have done better with my angle grinder. For some reason I decided to install those frickin' venturis in my carb, but they looked weird to me. NOW I know why. Like Jeff said, he didn't cut them right. (Jeff I'll be contacting you about straightening out my beautiful Glazed Nikki!) The angle is wayyyy too drastic. I haven't run my carb yet, as Gus is an ongoing build, but I'm glad I didn't. From the sound of things it wouldn't have idled anyway. Unfortunately, I now have to tear apart my carb again to try and sort out the mess this fool started. *sigh*

Here is a pic of the carb I built myself. I obviously wasn't interested in cutting corners by the looks of it. I did everything else on the carb myself, with the help of a local Indianapolis carb building shop (for the plating of the main body). Also went ahead and machined my own custom air bleeds, and thinned my throttle shafts the CORRECT way.

Jeff, I'll be contacting you about making the necessary corrections/adjustments. I'd also like to get some tuning info from you, and pick your brain about making this setup right.

Jamie

 

PM sent.

By the way, that's a sharp looking carb. Doesn't look all fisher price like SVT's lol.

 

Very nice. Did you paint or powder coat? Did you media blast to get everything so clean before finishing. I want to make a carb look this good but want to make sure the technique I use to finish it is correct and lasting.

 

I masked off the throttle body of the carb and painted just the edges of it with black ceramic brake caliper paint. The gasket mating surfaces were then un-taped when the paint was drying. The brake caliper paint sets up VERY hard, and I use it for most applications. It is very sensitive to humidity though. Make sure you paint at 50% RH or less. Otherwise the paint hazes up and turns white from condensation and ends up looking like crap.

The main body of the carburetor was media blasted and actually re-plated. I had both the blasting/cleaning and the plating done by Promax Carbs on Gasoline Alley in Indianapolis (PROMAXCARBS.COM). They are a 2-3 man shop, and did a GREAT job on it. Cleaned everything out after they got done blasting, and after plating it looked like brand new. Very professional, and I would recommend giving them a call. You could probably just ship them your main body and then have them ship it back. They also media blasted the air horn, and then I just left it raw aluminum when they got done, or may have possibly clear coated. Don't recall. I think I just left it raw. The aluminum should lightly oxidize to protect itself, but won't rust.