R1 Carbs (lots of pics)

[datzenmike]

They look too small. Maybe the vacuum signal used to raise the slide? My R-1s are boxed up.

[Keg86]

After reading through this thread and seeing some conflicting/confusing and sometimes vague information on how to tune these carbs I thought I would throw together a post on exactly how I did mine for my 1972 510.

 

First my engine specs:

 

L20b with a U67 head

Mild Cam Regrind (came with motor, unsure of specs)

Old Nismo Header

2.25” custom stainless exhaust W/ Innovative Engineering Wideband O2 Sensor (for tuning these carbs specifically)

 

 

Ok, now that that is out of the way, I got my set of 2000 R1 Caruburators (98-01 will work) on ebay for $150 and set to work. I sourced my intake manifold from Bogg Brothers in the UK ( http://www.boggbros.co.uk/ ) for ~$300 and verified their L20 intake manifold flange using my cad model to make sure they have a good layout. (Note: their manifold comes with a bar between the two halves that you have to cut out picture below) I also asked for them to give me an individual vacuum bung on each intake runner so I could manifold them to provide vacuum to my B210 brake booster. I liked the idea of manifolding them over just running one bung off of cylinder 4 (their typical seen on other manifolds from this thread). I also sourced my throttle cable, choke cable, and main jets (170s and 180s just in case) from Bogg as well. I got everything in the mail within a week and installed it. Note: I am not using vacuum advance but haven’t had an issue with it.

 

 

Initial tuning:

Idle air screw 3.5 turns out

Nonadjustable stock needles

180 main jets

 

A/F results from wide band:

Idle – 13:1

Mid – 14:1

WOT – 15-16:1

 

Here is where an issue with these carbs on the l16-20 engines comes up. Because of the proximity of the float bowl to the headers as the engine/headers get warmer the AF Ratio climbs and climbs. I saw as high as 19:1 on a long freeway cruise (had to pull over, let it cool even though the temp gauge never changed) and had to limp home. Need to build a heat shield.

 

This is the point that I knew I needed to get a little deeper into the carbs. Since I had the stock nondjustible needles so I called dynajet to get their tuning kit. After completely confusing the sales guy by explaining what I was doing with the carbs I was transferred to their Lead Carb Tuning Engineer. Sadly, I forgot his name but this guy knows his shit. He knew exactly what I was doing and steered me towards their 4165 Jet kit ~$125 (http://www.dynojet.com/pdf/4165.pdf includes adjustable needles, an assortment of main jets, larger idle jet, etc)

 

Now, this part is important, this carb magician told me to buy 4 (buy 5 they are tiny) of their DCO500 Corrector plugs ~$2.00. These plugs go in the main air jet (see picture below). This jet, according to him, works by allowing air into the main jet and aids in fuel emulsification. This system works great with the stock R1 Airbox but if you remove the airbox and increase the size of the main jet you get a compounding problem that exponentially lowers the fuel (increasing the air) going through the main jet. So a 180 jet will flow only marginally less fuel than a 200 and worse as you go up. (Read Main Air Jet section here http://www.dynojet.com/jetkits/jetkit-info.aspx )

 

 

Once I got the jet kit and plugs I installed everything and Tune 2:

Idle air screw 2.5 turns out

Adjustable needle at the midpoint (as directed by dynajet)

180 main jets

 

A/F results from wide band:

Idle – 12:1

Mid – 13:1

WOT – 11:1

 

Installed the 170 jets I had from before and Tune 3:

Idle air screw 2.5 turns out

Adjustable needle at the midpoint (as directed by dynajet)

170 main jets

 

A/F results from wide band:

Idle – 12:1

Mid – 13.25:1

WOT – 11.5:1

 

 

So now, using the same main jets I’m quite rich but everything else seems good. So I needed to order more main jets. Since you can use the main jets from a Weber 32/36 DGV I ordered a couple sets of jets 150s (Part number – 73801.150) and 160s (Part number – 73801.160) from Carbs Unlimited (http://www.carburetion.com/Weber/WeberDGEVParts.asp). I received the parts in 2 days and installed the 150s.

 

Tune 4:

Idle air screw 2.5 turns out

Adjustable needle at the midpoint (as directed by dynajet)

150 main jets

 

A/F results from wide band:

Idle – 12:1

Mid – 13.8:1

WOT – 12.5:1

 

That is as far as I have gotten but I might go down to the 138 jets that came in the dynojet kit just to see if I can get my WOT up to ~13 consistently and I’m probably going to have to have to richen up the mid a little once I do that. All in all it runs like a completely different car. It’s much smoother with a super quick throttle response. It doesnt even compare to the 32/36 I had in there before. Hope this all helps someone. 

[MantisX620]

Good info, thank you Keg86. Those air jet plugs would explain why im having to run 215 jets just to stay in the 12s at WOT. I still have some 170 main jets laying around, I think ill try those air jet plugs and see if my range gets a little more linear with the 170s installed. Any reason why you are turned in so far on your idle screws though? Wouldnt a leaner setting be better off? What timing are you running at by the way? I have mine somewhere around 13-14 BTDC.

 

MantisX

[Keg86]

Yeah, I hope it helps and let me know how it goes. Also, i cant stress enough to buy 5 or 6 of those plugs. They are TINY and i dropped one followed by 20min looking for it. As for timing, I am at ~16 BTDC if i remember correctly running mid grade gas. The only reason i am in so far on my idle air mix is because i haven't changed it since i set it up with the dynojet kit. I HATE doing those screws because you have to wait till everything is hot to get an accurate reading and always burn the shit out of your knuckles on the headers. I'll probably bring that up to 13:1 eventually but since it is really only the idle that is effected i am procrastinating. 

[MantisX620]

How are you guys syncing these carbs? Would a bench sync suffice? My plan otherwise is to tap my runners and hook them up to a motorcycle sync tool? Im also looking to put some weber 45 DCOE velocity stacks on how Dadszun did.

 

MantisX

[Suplexilicious]

I originally started welding a intake together but they need to taper for the head and carb to have a nice transition.

Any chance you have the 3D printer files for these manifolds or ended up casting some?

[Keg86]

I just did a bench sync and it seems fine. I put a vacuum port on each runner to sync that way but it didn't quite workout in the way I had hoped.

[G-Duax]

I always use the hand held carb synchronizer, and do it both at idle, when the slides are sitting on the stops,

and at just off idle, where all 4 slides are lifted off the stops.

The first is for making sure all 4 are idling the same,

and the second is for making sure all the linkage or cables are adjusted correctly.

I have seen so many youtube (youboob?) vids of poorly sync.ed throttle bodies, and carbs, it's like they can't figure what they are dooing wrong.

The engines always seem to have one, or more cylinder go dead when they just come off idle do to the one carb, or throttle body not opening at the same time as the other.

[slingshot532]

https://www.flickr.com/photos/slingshot532/shares/0572Z9

 

 

Just got done rebuilding my motor. Got it started tonight. It's a pickup ka24e block with frontier ka24de head, Brian Crower cams, Light flywheel, Brian Crower valves, cheap EBay 4 to 1 headers... I had these carbs with the stock pickup head and it ran great. So far it's running good. I have a new electric pump and it's too strong so the carbs are overflowing from the vent tubes. The carbs are in the way of the battery. Stupid stuff. I do not recommend the ka24e to ka24de head swap. Just start with a ka24de and get the E Pistons. It's a lot of work and half assing stuff. But for the record it does work. Once I get the exhaust on I'll post more.

[slingshot532]

Somehow a valve adjustment shim came lose and broke in half. It chipped my exhaust cam. The motor had the classic ka24 valve tick so I took off the valve cover to check it out and sure enough.

[angl71-521]

nice  :thumbup:

[MantisX620]

Hey guys, my carbs were basically pissing gas out of any open orifice today. In port 1, there was a small pool of gas even. I've taken them off to inspect them, but any idea why a carb would overflow like that? I'm hoping something is just clogged.

 

Unrelated (or maybe not) where can I get a replacement diaphragm cover?

 

Thanks

MantisX

[Stoffregen Motorsports]

Stuck float due to wear, fuel pressure too high or dirt.

 

That's my guess.

 

What PSI do these carbs run at?

[MantisX620]

5psi I believe. I gave them a good cleaning and all seems well now. I was low on gas so maybe it was dirt.

 

MantisX

[Loryde520]

I had the same problem on my recently installed Mikuni R1's. The second carb in started to squirt gas out of the tiny air jet. I installed a 1-4 psi fuel pressure regulator and problem solved,....for now. I ordered 4 new needle and seat kits from the local Yamaha dealer just in case the problem arises again. Apperently the o-ring around the outside of the seat tube can leak and cause the same problem. It's like the floats aren't shutting off the gas flow. Mine carb was actually bleeding fuel into the intake tube and causing a hard start issue. I am running a stock mechanical pump with a Holley regulator.

[MantisX620]

Carb #1 pissing gas again and coming out the overflow. I think it may be related to runner 1 as its the only one that has a nipple on it for a vacuum signal. Gonna check the disti and the hose to make sure there are no leaks.

 

On another note, before it started pissing gas again, I made the changes suggested by Keg86 and the advice given is spot on! I blocked off those ports with solder and installed smaller jets. The truck has never run better! Pulls to redline and doesn't take long at all doing it. First time ive gotten this truck do 95mph lol. I have .175 jets in it and AFRs are:

 

Part throttle: 14.3-13.7

Full throttle:  12.6-12.9

 

I think a .170 or .165 will be slightly better, put it pulls great as is.

 

Im not too comfortable with the solder though as gas might weaken it. Im thinking ill put some jb weld down the holes instead. I was gonna get the plugs meant for it, but they charge $14 shipping on 3 dollars worth of parts and im a cheap ass.

 

MantisX

[Keg86]

Nice man! I'm glad to hear that it is working for you. Plugging those ports makes all of the difference. I finally got mine dialed in to 13.5-14 at WOT, 13.5-14 at part throttle and idle at 13 flat. Sadly, i only got one reading cruise then my O2 sensor died so I'm hoping it is still good cuz i have SMALL 138  jets in there for my L20. 

 

The pissing gas thing has happened to me too. I found that it was related to a vacuum leak between the carb and the valves. Somehow, if there is a leak there it starts going crazy, not sure why. When it has happened to me Ive tightened my connector boot clamps and that seemed to stop it. I'm running the R1 fuel pump if that makes any difference. Sucked cuz it just starts pumping like crazy until you turn the engine off with key out and find the leak.

 

Also, just realized that my profile picture was taken when i was pulled over after the first time it puked gas all over my headers while out on a cruse. haha Datsun memories.

[Stoffregen Motorsports]

What type of pressure regulator do you have?

[Keg86]

My R1 Fuel pump from 98-02 doesn't use a pressure regulator since it is specifically for those carbs and internally regulated to a outlet line pressure of 3psi. It is a really nice electric fuel pump option since it uses simple two wire 12v power, controls itself and are like $25-30 on ebay.  

[Hix1985]

Anyone making Intake manifolds state side yet?

[Tom1200]

Just an FYI; on the FCR carbs I have the regulator adjusted to,just over 2 psi. Anything above 3 psi and it seems there is some love of fuel weeping past the float needles. Fuel may not leak out the carbs but you notice the car being rich at idle, really,obviousmifmyou,have an A/F ratio gauge. I try to keep the revs above 5k all the time (some turns it drops to 4800) and do not have fuel starvation issues, well at least when I remember to top the fuel cell.

 

Tom

[Stoffregen Motorsports]

I guess that's what I'm getting at. Sounds like the weeping is a result of too high fuel pressure.

[Keg86]

Yeah with the standard mechanical fuel pump pushing 3.5psi you might see some fuel weeping but that wasn't the issue that i saw. I have a wide band A/F and even when it was dumping fuel out of the overflows my ratios were still rock solid also since i am using the fuel pump from the bike the carbs came from i think the pressures are good. Since i fixed all my carb boot connections it hasn't happened again (fingers crossed it wont). For the life of me i cant figure out why a loose boot connection would cause it to dump fuel out the overflows tho.

 

Hix1985 - I haven't heard of anyone commercially making them in the states yet. However, i got mine from the Bogg Brothers in the UK and the price was pretty reasonable and i had it in my hands a week after i ordered it. I would totally recommend them. They put these carbs on everything and are super knowledgeable if you have any questions. That is my $0.02

[ap72license]

My buddy Tony can make you a manifold, he just made me one for the zx14R ITB's to bolt to my Ford 2.3L. He's a little backed up on work right now but he always appreciates more business.

[G-Duax]

I just used normal Mikuni carb spigot mounts on a Weber DCOE style manifold.

Although I'm using Mikuni smooth bore VM carbs, someone could possibly do something simular to mount the FCRs.