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Probably time I post an update on my carb conversion, and I also need some help...

From pics above, I was in the middle of swapping these onto an '87 Cabriolet but ended up getting a Mk2 Golf with a gunked up CIS system (easy decision). :D

Carbs are Keihin CVK, likely from a '96-'03 Ninja ZX7-R. After chasing down a couple of vacuum leaks, and hooking up the distributor advance, I am at the point where I can get them to fire up and idle. They'll only run with the choke (really a fuel enrichment circuit) engaged... I have a couple of issues I could use help with, here's what's happening:

  • Starting when cold takes a few attempts before sputtering to life.
  • As soon as I disengage the choke circuit it will die, regardless of how long it's been running.
  • I am using an AEM wideband O2 gauge.
  • I have the pilot mixture screws (fuel side) about 4-4.5 turns out, which concerns me as they loose "snugness" around 5 turns out so I know I'm pushing it.
  • Once warmed up with choke circuit still on and throttle 100% closed, AFR is around 12:1 - 13:1. If I blip the throttle off idle it bogs and dies.
  • If I crack the throttle plates using the thumb screw, it is my understanding that the plates uncover more (up to three) pilot holes. However, turning in the screw (opening plates) lowers RPM quickly and AFR progressively goes off the gauge (~ 17:1) and will die.
  • When warmed up, if I give an aggressive throttle pull it will bog a second then rev up. The AFR goes lean off the gauge though...

I don't have air filters yet (ordering tomorrow). I noticed if I cover a bellmouth or two with my hand, it revs up a bit easier and healthier-sounding, but still lean off the gauge.

All the above is leading me to understand I'm way too lean all around... So I removed the carbs, opened the bowls (not too bad inside) pulled the pilot mix screws and started cleaning. See pics below.

My main jets are 148, and pilot jets are 38. It's a stock low-compression 1.8L 8v, so any recommendations on either jets?

Some Pics:

Carbs with throttle linkage. Carb faces (with bellmouth) not installed yet here.



Bowls a little gunky, but otherwise decent:



For fuel I am using the stock CIS in-tank "lift" pump with new 5/16" hoses to the front and CIS stuff removed. I did try an under-car low-pressure pump but it wasn't moving any fuel, so I bypassed it.
In the bay I have a transparent filter, then another filter that has a second 1/4" outlet functioning as a return. This setup puts 3 PSI to the carbs.
I had tried using the Holley adjustable FPR (laying on strut tower) in a return arrangement, and it functioned the same as this setup...




Super-tight clearance to the firewall with carb bellmouths on:

 

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What does your fuel pressure do when you open the throttle? Does it hold or does it drop off?

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^ Good question, I was always watching AFR, but never paying attention to the FP gauge...

It's going to be about a week before I get the carbs back on. I am cleaning them and ordering up filters which will need some trimming for fitment.

What would the fuel pressure indicate? I'd assume at idle the 3 PSI reflects closed fuel ports, and at open throttle it should drop a tick as the floats drop and let more into the bowls?
 

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Yes, it should drop a little bit, but not a lot. If it drops too much you may want to try losing the return line and just running a dead headed system.

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Finally some success, cleaning the carbs was the key! :laugh:

I was told they had been cleaned before I bought them so I didn't think to open them up and check... I did a light disassembly on them, pulling the pilot (idle) screws, pilot jet and main jets. It's amazing how tiny the pilot jet holes are, and easily gummed up... I sprayed nearly a can worth of carb cleaner forward and reverse (where possible) through the pilot and main circuits.

I have the pilot screws about 2-1/4 to 2-1/2 turns out which is much more appropriate. The throttle plate thumb adjuster works exactly as expected now, raising and lowering the idle speed properly. The starter circuit (choke) works much better, and I can close it off after it warms up for a couple of minutes.

Once warmed up with choke off, I've got the AFR fluctuating around 13-15 with idle RPM around 1,000. If I blip the throttle I am still getting an bit of hesitation before revving, and an occasional backfire out of #4 cylinder. It seems to get better the longer I run it though.

Fuel pressure at idle is pretty steady, mostly at 3 PSI but randomly dipping to 2.5 PSI and back up. I added a 1-way valve after the return port, which I know is functionally pointless but helps put a little bit of resistance in the line.

For idle AFR, should I open the fuel screws a bit more and run it richer? That might help with the throttle blips off idle going lean?

And I assume my next step is trying to drive it and put some load on the engine? No real way to ascertain how the Main & Needle are functioning by just revving it without load...
 

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I also had a scary incident and have to revise my throttle linkage...

I was standing in the drivers door revving it up with the pedal and the cable snagged on one of the bolt heads (two small bolts with blue locktite) and held the throttle open about 50%. It revved up to redline for what felt like an eternity (probably 5 seconds) while I fumbled around and shut it off... I'm not sure if the ignition system was cutting spark or I was floating valves...

 

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I believe you are correct on that, being that CIS is so sensitive to fuel pressure. Also explains why the fuel pump relays are so particular...

This is a bone stock, low compression, small valve 8v with hydro lifters so it wouldn't surprise me if it were floating valves around 6500...
 

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I believe you are correct on that, being that CIS is so sensitive to fuel pressure. Also explains why the fuel pump relays are so particular...

This is a bone stock, low compression, small valve 8v with hydro lifters so it wouldn't surprise me if it were floating valves around 6500...
If that is a single valve spring motor then that is probably the case. I believe the 16v was dual valve spring from the factory but my memory is foggy. I had autotech cams and valve float hit right after 8k and made a funny sound.
 

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I finally drove the car for the first time (ever) yesterday. I've got the idle A/F ratio pretty good between 12-14. Now I need to move the AFR gauge into the dash so that I can see what's going on under load.

The car is pretty soft all-around, and the carbs definitely need some tuning, but I am so happy to finally have driven it!

I did a quick revision on the throttle linkage to eliminate the cable snag issue. I need to tweak the cable clamp setup, but this works for now.



And here's a video of it running. Hopefully I can embed this correctly:

 

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Question for you carb’ed guys.
I have a 1.8 16v corrado I recently converted to bike carbs.
Fz1 carbs, 170 jets, bogg bros manifold, fz1 fuel pump and a 1-4 psi fpr.
The car runs but idles at 2200rpm.
I can’t adjust the idle at all. Even by bringing the fuel pressure down to 1psi, nothing.
I’m at the end of my rope trying to sort this thing out.
Any ideas?



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Vacuum leak?

What's your AFR @ idle?

Is your throttle cable allowing the carbs to close the whole way?

Have you cleaned and baseline adjusted the carbs?

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Vacuum leak?

What's your AFR @ idle?

Is your throttle cable allowing the carbs to close the whole way?

Have you cleaned and baseline adjusted the carbs?

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Not sure about vacuum leaks. The only vacuum line I know of is the one from the manifold to the brake booster. That one is fine.

No idea of the AFR’s

Throttle cable isn’t connected.

Carbs have been cleaned and balanced.


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I know this is an old post and I think I’ve read most of it. So I bought a setup of carbs, fuel pump and msd from someone who had this on their mk2.

I’m putting it in my mk1 16v swap but holy **** this radiator and coolant neck on the head is giving me so many issues. Initially I had a civic radiator cause I saw it mention quite a bit. I didn’t like they way it looked or how we had to angle it so had got one from S&P automotive. It was a tucked radiator for carb swaps and I sent it back as I would have to run an in-line fill for it and the inlet/outlet where on the passenger side and there was no room at all.





So I sent that one back and got their mini tucked version and again didn’t like it. The inlet/outlet was on the drivers side and running coolant hoses was just ugly. Had to buy these metal flexible ones and there was literally no room from the bottom of the carb to the coolant neck on the head to get a hose clamp on. Plus running the lower hose down and u see the front engine mount just looked awful





So now I’m on radiator 4, scirocco style with and end tank and inlet/outlet on passenger side. But again the issue I’m having is with the bottom of the bike carbs and coolant neck.

I’m assuming at this point I’m gonna have to get a new intake manifold where the carbs are angled more up or do some serious fab work to the front core support.

This is how the carbs sit now, would it be ok to angle them more






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I know this is an old post and I think I’ve read most of it. So I bought a setup of carbs, fuel pump and msd from someone who had this on their mk2.

I’m putting it in my mk1 16v swap but holy **** this radiator and coolant neck on the head is giving me so many issues. Initially I had a civic radiator cause I saw it mention quite a bit. I didn’t like they way it looked or how we had to angle it so had got one from S&P automotive. It was a tucked radiator for carb swaps and I sent it back as I would have to run an in-line fill for it and the inlet/outlet where on the passenger side and there was no room at all.





So I sent that one back and got their mini tucked version and again didn’t like it. The inlet/outlet was on the drivers side and running coolant hoses was just ugly. Had to buy these metal flexible ones and there was literally no room from the bottom of the carb to the coolant neck on the head to get a hose clamp on. Plus running the lower hose down and u see the front engine mount just looked awful





So now I’m on radiator 4, scirocco style with and end tank and inlet/outlet on passenger side. But again the issue I’m having is with the bottom of the bike carbs and coolant neck.

I’m assuming at this point I’m gonna have to get a new intake manifold where the carbs are angled more up or do some serious fab work to the front core support.

This is how the carbs sit now, would it be ok to angle them more






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Are you using an aftermarket coolant neck for bike carbs?



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I used a stock radiator and radiator support and ABF waterneck but that was in a mk2. I too had the civic rad and wasn't a fan of the look. I didn't run filters though, so I had a bit more clearance. Could run the trumpet screens that some people have, they are mentioned in the thread.
 

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Hi think this is the right place to ask this. So I've got a carbed Ce2 Jetta 1.8, and Ive put a crossflow head on it and I'm running r1 carbs. I'm using an intank pump to a surge tank under the car then to a r1 bike fuel pump, and have used a fuel pump wiring harness from the fuse box to the pumps from an digifant golf. I've tried to use the digifant fuel pump relay in the relay position 12, but it does not work. I've had the car running by just using a jumper lead in place of the relay. I've tried to search online for a solution and think i need to use a fuel pump relay from a early mk2 kjet or cis. So can anyone tell me before i buy a new relay that if i get a early mk2 fuel pump relay and plug it into slot 11 will this work or am i better of wiring a relay externaly???
 

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From my research position 11 in a CE2 fuse box should be the horn relay. Position 12 should be the fuel pump relay. It sounds like you are using the stock in tank pump from the Digi, then the R1 pump in place of the Digi main pump, correct? If the R1 pump is in place of the main Digi pump and using the original wiring it should run off the original realy and fuses.


Have you checked your ground and switched signals in the fuse box? Have you tested the relay to make sure it is working properly?

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