R1 Carbs (lots of pics)

[VintageRice]

Good tips Mikey ! ! I'm educated once again.

 

I'm gettin a stat......stat ! ;)

[VintageRice]

Your lean. Popping on decel is a symptom of being too lean as is the lean misfire (carb cough)

You may need to increase your pilot jet size. On the carb that is coughing adjust your idle mixture screw until it no longer coughs.

 

Really? Ok, well I'll definately consider that. But then why did the popping/backfiring improve with removing fuel pressure? (these carbs are rated for only 3psi)

 

And also I've heard coughing carbs can be from rich or lean depending. But thats just what I heard from a backyard hotrod/ oval track racer guy.

 

Also, when you drive a subaru brat at 40mph, trun the key off, pump the gas, then turn it back on it goes BANG !! (personal experience) :) :) backfire is the result of excess fuel passing through the cylinders into the exhaust yes? I figured that's where my deceleration popping is coming from. But I could definitely be wrong too.

 

Wheres all the carb tuning guys when you need them ? ? ? :D

[Drummerboy4as]

I'm just going off of what I know from tuning my motorcycle that also has a Mikuni carb.

 

Popping on decel (closed throttle, slowing down) is cause by a lean condition or exhaust leak.

Popping in between shifts (open throttle, close throttle, shift, open throttle, bang) is caused by a rich condition, raw fuel being ignited in the exhaust.

A carb fart or lean misfire is caused by a lean condition in the intake manifold. Could be a leak as well. I used to know exactly what cause a lean misfire but have since forgotten. I'll do some digging and get back to you

 

Edit: the lean misfire happens when the throttle is open and the air velocity of the intake doesn't yet match the velocity of the engine. The carb can't yet compensate by adding fuel so a lean condition occurs. If you are getting popping out of a single carb at idle you most likely have a leak in that runner somewhere.

[VintageRice]

I'm just going off of what I know from tuning my motorcycle that also has a Mikuni carb.

 

Popping on decel (closed throttle, slowing down) is cause by a lean condition or exhaust leak.

Popping in between shifts (open throttle, close throttle, shift, open throttle, bang) is caused by a rich condition, raw fuel being ignited in the exhaust.

A carb fart or lean misfire is caused by a lean condition in the intake manifold. Could be a leak as well. I used to know exactly what cause a lean misfire but have since forgotten. I'll do some digging and get back to you

 

Edit: the lean misfire happens when the throttle is open and the air velocity of the intake doesn't yet match the velocity of the engine. The carb can't yet compensate by adding fuel so a lean condition occurs. If you are getting popping out of a single carb at idle you most likely have a leak in that runner somewhere.

 

Awesome, hey thanks for the help. I'll definitely look into this. The leak in a runner could be a possibility given I built the entire thing lol.

 

Thanks!

[slingshot532]

I have been driving my car, it is running strong but still working stuff out. I took an extended drive on the freeway and it started to feel like the throttle was sticking. I got off the freeway and sure enough the idle was high, I pulled over and tryed to lower the idle with no luck. Meanwhile the car started to over heat, I got back on the freeway and the temp slowly dropped. It never got over 3/4 on the guage. the next day I whent to start the car and it was leaking from the water pump (something I should have changed befor I put the motor in). I replaced the water pump and thermostat and it runs right at the mark. Still havent figured out the high idle, it hangs up if you lightly push the pedal, if you mash the pedal and just let it go the idle drops back down. I may need a stronger return spring?

 

I also have a short in my turn signal somewhere, the flasher fuse blew, the guages are also on this circut. I think that is in the turn signal comby switch.

 

If I decel after a long full throttle run then get back on it, it stumbles and missfires befor accelerating. Sometimes it takes a while to catch up. The car is still running rich could this have somthing to do with it?

 

Stoked to see everyone making progress. Can't wait to see the turbo and the L16 running.

[Drummerboy4as]

Definitely sounds like a rich condition. When you blip the throttle does it return to idle quickly or run on for a second before returning?

 

Stumbled on this recently. It's written for a Yamaha Road Star but the principles are the same and the carburetor they are talking about is functionally the same.

http://weislake.com/sig/mucker/carb/carb%20tech3.pdf

[Drummerboy4as]

Is anyone else experiencing low manifold vacuum with this new setup?

I have 2 ports, 1 for the brake booster tee'd off to the tranny and 1 for the dist advance. I'm only getting about 10hg from each while I should be getting 20hg.

Normally it wouldn't be an issue but I'm using an auto tranny and without the proper vacuum it won't shift correctly.

I'm still trying to nail down whether it's a vacuum leak or if the large diameter of the carbs is not giving me enough intake velocity.

I'm running an A87 head so I don't think it's a matter of the head choking the intake.

Thoughts?

[VintageRice]

Glad this thread got going again. Good tips all around. :hug: :hug: :rofl:

 

 

Tonight I put in a stat, and lifted all my needles to the highest/richest setting. I figure looking at the taper on the needle that I'll gain a fair bit more fuel off idle and stay about the same at wot. The main is pretty much wide open anyway at wot cause the end of the needle is barely in the hole at any position really lol.

 

Hopefully running at proper temp and a little richer will bring good results. :) We shall see!

[slingshot532]

Thanks Drummerboy. I will study the info.It seams like all the carb how to pages have one piece of unique info that is totaly healpful, or sheds a differant light on tuning.

 

As far as the idle issue , if it is at idle and idleing high, I blip the throttle and it drops right back down where it should be. it reminds me of the high idle carbs do to help the car warm up and run better when cold, but it dose it all the time... It must be because it is rich. I just read that and it sounds like having the choke on. That would explane the very high idle when it was warmed up after driving on the freeway for 10 min.

 

I have not checked vacuum pressure, I have noticed my brake booster may not be working as good as it did with my old motor.

[VintageRice]

Ok, took it for a drive with the stat in, heater works much better lol.

 

 

I adjusted the needles all the way rich. Drove it. It popped close to the same on decel but popped the enitre time during idle once warm. pop pa pop pop pop pa pop pa pop pop papa popidy pop pop...

 

Adjusted them all the way lean(scary word) ran about the same as it did in the middle adjustment.

 

 

 

 

 

On a side note, I think the engine finally running at a proper temp stopped the little bit of carb cough on idle so thats good.

[datzenmike]

It may be all the way rich... but only as rich as that particular needle and jet is concerned. A smaller needle and or larger jet would be even richer. A wide band O2 sensor and gauge would lay this to rest.

 

I would also like to know why the manifold vacuum is so low. Is it just that one or are all R1 carb set ups like this???? Maybe some others should connect a vacuum gauge to their manifolds.

[Dirttrack510]

For what it's worth, I had that boiling issue on my race car and I took the thermostat out and removed the guts of it and then put it back with just the little crossbar piece still attached to help remove air bubbles. I've never had another overheating problem. I can't say it's a great idea for a street car though, as my car is strictly a race car and is flat on the floor/wide open throttle at all times. I guess it's worth a try though if nothing else works for you.

[VintageRice]

It may be all the way rich... but only as rich as that particular needle and jet is concerned. A smaller needle and or larger jet would be even richer. A wide band O2 sensor and gauge would lay this to rest.

 

I would also like to know why the manifold vacuum is so low. Is it just that one or are all R1 carb set ups like this???? Maybe some others should connect a vacuum gauge to their manifolds.

 

I know. By "all the way rich" I meant as far as I could adjust the needle at this particular moment. I was just trying to see if there was noticable changes from going richer or leaner. And there was.

 

Adjusting hte needles takes a few minutes. Changing jets you have to pull the carbs off. Plus get different jets lol. I was just working with what I had for fun.

 

I'd also like to mess with the mixture screws but DANG they are hard to get to when the carbs are on. Pretty much impossible to adjust accurately with carbs attached. O well.

[slingshot532]

I found my high idle problem, the carbs where coming out of the radiator hose couplers i made. the back 2 pulled all the way out finally and it wouldan't start.I will up grade to fuel filler line. I tracked down a short in the turn signal switch, someone cut the horn wire and spliced in a new wire to it by wraping the wires together and taping it.fixed that and the fuse dosen't blow and the guages work. Yaay!

 

Also found a way to instal a return spring, just need to find the right spring.

[VintageRice]

Progress rules. :D

[spudly13]

It may be all the way rich... but only as rich as that particular needle and jet is concerned. A smaller needle and or larger jet would be even richer. A wide band O2 sensor and gauge would lay this to rest.

 

I would also like to know why the manifold vacuum is so low. Is it just that one or are all R1 carb set ups like this???? Maybe some others should connect a vacuum gauge to their manifolds.

 

i just got back from the dominican today. ill hook my boost gauge up to my intake tomorrow and let u guys know what kinda vaccum im runnin

[datzenmike]

Good. I've thought about this and can't see why it would be normal to be so low. Idle should be 18-20 range. Big overlap cam maybe 15.

[Farmer Joe]

now a point that hasnt been made is that it sounds like were only getting a reading from 1 of the runners...

 

am i correct in this?

 

do any of the r1 guys have an intake with a balance tube, or is it just single runners youve tapped?

 

mike, a normal reading is usually taken from somewhere thats a common plenum.. whereas, the single runner will only give you the reading from that cylinder.

 

thats just what im pickin up... id say if the intake has a 1/4in or 3/8in balance tube connected to each runner for 1 valcuum source, that would prolly get the 18-20hg reading your lookin for..

[Drummerboy4as]

I've been giving the vacuum problem some thought and there's really only two things I can come up with that might cause the problem.

 

The first and most likely in my mind is that the vacuum isn't being pulled from all cylinders. The problem with that though is that hooked up to 1 runner I get about 10hg with the needle bouncing with every intake stroke. When I have cylinders 1 & 4 hooked together I still only get about 10hg.

I have no way of testing the hypothesis as I have no ports on runners 2 & 3. If necessary I will tap 2 & 3 and run all 4 hoses to a manifold. I'd like to avoid this until it's been "proven" that this is necessary.

 

Hypothesis #2: the intake manifold starts at 40mm and tapers down to just oversize of the intake ports. There is a 1/16-1/8 inch lip around the ports that doesn't match the manifold. Could this shelf be causing turbulent air and decreasing my intake velocity thereby decreasing my manifold vacuum?

 

The other thought that I had was that maybe 40mm was too much for a 1600 but I've read that 1600 pintos are using 40mm webers no problem.

 

L16, A87 head, to my knowledge stock cam, stock exhaust manifold with glass pack, R1 fuel pump

[spudly13]

im showing between 17-20 psi of vaccum

[Drummerboy4as]

Pulled from where?

Engine specs?

 

[spudly13]

pulled from the #2 cylinder intake runner. Stock l16 with a ported head. homemade turbo header.

[spudly13]

 

 

 

 

Hopefully this works... i was so mad yesterday when it broke

[Drummerboy4as]

pulled from the #2 cylinder intake runner. Stock l16 with a ported head. homemade turbo header.

 

Hmm. You have an intake plenum too right?

[spudly13]

yeah