R1 Carbs (lots of pics)

[G-Duax]

I would think so, since they are meant for gravity feed.

But I will be bypassing fuel back to the tank, that will lower the pressure seen at the carbs,

and a lower static fuel level (float setting) will also help.

But I am prepared to put a 1 psi check valve in on the return, without a bleed jet, and that will drop the pressure at the carbs to that.

[Tom1200]

On my flat slide carbs I run no more than 2 psi. 2.5 seems to be the tipping point where the float needles start to leak. At 3psi you'll start getting fuel spilling over.

 

Tom

[slingshot532]

Update on r1 carb status. Still running strong after a couple years. Running frontier dualcam head with Brian Crower cams, valves, springs and retainers. Block and tranny are from a single cam pickup, distributer is from L series motor. Diff is R180 front diff from 4x4 Nissan pickup. Fuel pump is a K and N carb electric pump puts out 3si. I add 1gallon of VP M5 to a full tank sometimes to compensate for the higher compression and it runs very smooth. Super fun.

 

chttps://www.flickr.com/photos/slingshot532/shares/w31XLF

[Tom1200]

Nice I've had the flat slides on my car for over 10 years now and they've been flawless as well. Mine is a biased opinion for sure but I think the bike carbs are the way to go. Nothing wrong with DCOEs but the bike carbs flow more and for me have better throttle response.

[G-Duax]

You know, K&N makes angled filters, right ?

[banzai510(hainz)]

Cool
do these carb have accell pump or just CV as most bike carbs?

[datzenmike]

R1? CV . When the throttle is opened suddenly the slide can't react fast enough and the engine vacuum draws in extra fuel forcing a rich condition. At least that how SUs work. The SU's damper oil acts like a shock absorber. Thicker oil causes the richness to increase, thinner to lean out.

[MantisX620]

Anyone have any idea why my R1 carbs would go lean (20.2 AFR on wideband) when I am slowing down to stop (Out of gear), and then richen back up to 14.5 after i've come to a stop at the stoplight? Everything runs as expected in every other part of the carb range except here. Im  going to check again for vacuum leaks but I cant think of anything else to check.

 

MantisX

[datzenmike]

Well I think most carbs go lean on deceleration. The mixture is set for the air drawn in at idle. When slowing down you're engine draws in more air that is does at idle so it will get very lean and why the exhaust may pop. It's just wasted gas anyway so the less you burn the better. Some 720s and maybe the '79 620 had a fuel shut off on deceleration. It turned the idle cut solenoid off so no idle gas can be sucked in when slowing down at highway speeds. It should save gas but really it just removed gas otherwise wasted out the pipe.

[G-Duax]

You don't need14.5:1 on decel, or idle.

Just like you don't want 14.5:1 when pulling hard, especially on a built engine.

Just at cruising speeds.

Best HP & Torque are obtained at 12.5 to 12:1.

 

On the newer EFI cars, the A/F will go off scale on decal, because the injectors will shut off when the throttle is closed at higher engine speeds.

[MantisX620]

I see what you guys mean. But, should'nt the carbs only go lean if im decelerating in gear? In my example above, I was decelerating out of gear which means the engine should idle as it would if im sitting still right?

 

MantisX

[G-Duax]

Stop worrying about it......

[datzenmike]

Take it up to highway speed and take out of gear and coast long enough and it will probably go lean then clear and then back to 14.w/e at idle.

[lowrider]

I finished welding up a manifold not for the 40mm R1 carbs, but for the 37mm FZ1 Mikuni carbies. The FZ1 carbs have a shallower mounting angle and are technically classified as side drafts versus the down drafts of the R1 carbs. This allowed me to build a more classic horizontal manifold. Don't mind the welds, I'm a bit rusty welding aluminum.

I have to make a vacuum manifold for the brake booster and then I'll be installing these on my 610 wagon.
 

[hendrik6073]

i used a second hand vacuum brakem pump for that purpose, one like this

 

[lowrider]

On 8/21/2018 at 12:57 PM, hendrik6073 said:

i used a second hand vacuum brakem pump for that purpose, one like this

 

I believe I am going to go the same route. I did some digging and the pump that you linked to is used on an assortment of late model Volvos. I plan on taking a trip to the local Pull-a-part this weekend to grab one.

Do you use a reservoir with the pump or is it plumbed straight to the booster?

[hendrik6073]

both can be done, it is not neccecery. I use a little reservoir because my headlamps are also vacuum powered. I use a festo switch to switch the pump on and off. switch

[G-Duax]

On ‎8‎/‎21‎/‎2018 at 11:57 AM, hendrik6073 said:

i used a second hand vacuum brakem pump for that purpose, one like this

 

 

Those are all over eBay for $50-$75 used.

They come on many Audi & VW cars.

I've bought 2 of them already, for projects, and another will go on my 620 when the bike carbs go on.

They have a built in vacuum switch, and will shut down when (going from memory here) at about 20" of vacuum.

Any of the cheaply built vacuum reservoirs, like Moroso offers, will work, but I found a nice small (about a quart) air tank with better connections.

 

Here are some of those pumps now: https://www.ebay.com/itm/Audi-Volkswagen-Brake-Vacuum-Pump-8E0-927-317-A/362420667915?hash=item5461f4860b:g:unoAAOSwTWZbf1B-

Edited August 24, 2018 by G-Duax

[frank88]

I've been reading all 55 pages this week and thank you to all who have contributed. Great thread. I'm pretty keen on giving this a go bit my main question is about vac lines. 

 

It seems there have been good results with vac advance when all the runners have been tapped but then what to do with the brake booster? Has anyone tapped the runners AND tapped into the number 1 runner for the booster?

 

Anyone run an electric vac pump for booster or just delete it all together?

 

I know there has been talk of this in this thread but limited confirmations or reports back. I'm trying to put a shopping list together for a reliable build.

Edited September 21, 2018 by frank88

[G-Duax]

See the post just above yours.

 

Audi Vacuum Pump is what I use on 2 different vehicles, along with about a 1 quart reservoir.

They run around $50 on eBay for a real nice one, and $65-100 for a chinese one.

Personally, I'd rather run a used one from Europe, than some POS out of china.

 

Edited September 21, 2018 by G-Duax

[frank88]

Thanks for that, not sure how I missed it before!

[hendrik6073]

is there some kind of compare list when it comes to jet's ? i would like to compare my 1.6 setup with others.

[datzenmike]

I'd like to have a starting point for 2.4 liters.

[hendrik6073]

1.6 i think my setup is not as it should

 

[ap72license]

displacement will have little to do with carb jetting, the exact model of carb, cam timing, intake and exhaust design, etc will all play a factor.  If possible I reccomend spending the money for a wideband oxygen sensor setup, or going a step further and a budget datalogging system.  Will make a HUGE difference when trying to tune.