914 Carb issue (I hope)

[GBG1000]

I recently picked up a 72 914 with IDF 40s. It was a 1.7 but I believe it has been upped to 2.? with new cyls, and has a carb cam.

It never ran very good, but did allow me to have some fun for a few hundred miles.

Then suddenly it started running very bad. I noted that fuel pressure was very low (0-1.5 psi), so figured I'd get a new pump and all would be well.

I also noted a huge difference in cylinder head temp from one side to the other. If I recall correctly, drivers side hot, passenger side cold, but I am not absolutely sure that the drivers side gauge corresponds to the drivers side cyls. I thought that was related instrument malfunction

I installed a new rotary pump with regulator, at 3.0-3.5 observed PSI, but that did not solve the problem.

I began to wonder, could it be a carb balancing thing. So I began to follow tuning advice from the Redline Weber site. What I noticed was that the drivers side carb (cyl 1-2) was responsive to adjustments. The Passenger side carb was not. It did not make a difference whether I closed both mixture screws all the way - absolutely no difference. Moving the Idle speed screw made no difference either.

When I put uni sync on barrel # 1 or #2, the car wants to die, but when I put it on #3 or #4 it makes no difference.

So I begin to think ignition. Detach plug wire from #3, check spark. Get good spark, no change in idle when I disconnect the wire. Same thing for #4.

When I try to detach #1 or #2 wire though, the car will not remain running. It must be running on #1 and #2 only.

The passenger side carb does get fuel, evident by strong squirt from accel pump (oddly enough- the drivers side accel pump does nothing - go figure!)

So- sorry for the long book, but I'm looking for some ideas. Is this a carburator problem, or something more synister?? The fact that neither #3 or #4 appear to be under power makes me think fuel supply rather than carburation, but the accellerator squirts plenty of juice.

Can I get some opinions and advice? Thanks in advance

[Curt914]

HI

Kinda having a similar problem myself.

My mechanic reminded me not to get too ahead of myself and get back to basics.

Fire, fuel and compression are needed.

So, looks like you need to check compression.

Pull all the plugs, open the throttle and run the starter

Cylinders should read about the same across all 4 and should be about 120lbs.

If your suspect cylinders are low, maybe check valve clearances.

If they are way low, well then, my condolences

If they looks good, I would investigate ignition. Are all the sparkplug wires going where they should be?

My drivers side runs cooler than the other side. I can feel it just standing there and also when I grab the intake manifold. And turning the mixture screws on the drives side has decidedly less effect on the running than the mixture screws on the passengers side. Right now I have the carbs apart cause I have been through the compression check an ignition.

Let us know what you find

Curt

[GBG1000]

Thanks for the input Curt.

I have never had more than 1 wire off at a time, and each plug emits a spark, so I know I have fire. And I don't suspect my timing is the culprit, because I don't think it would affect just 2 cylinders.

The fact that both barrels of the drivers side carbs are absolutely non-responsive to idle screw and idle speed adjustments leads me to suspect fuel delivery problem to that carb. - but why then does the drivers side accelleator pump squirt gas????

I got to thinking last night, that I could switch carbs from one side to the other and see what happens.

That seems like a very quick way to check if there is something seriously wrong with the drivers side carb.

I will also look to see if I can find my 15 year old (never before used) compression checker.

I will go out and check a few things and report back. In the meanwhile, Gurus, please keep the advice coming.

[Kevin Powers]

the dr side carb is getting fuel. check the idle jets. odd that the acc pump jet doesn't work on the carb that responds to idle/air mixture screw adj. if the jet cleaning works for awhile. your carbs may be due for a rebuild.

[Curt914]

Yeah, that carb on one side seems a bit odd. The barrels on one carb are independent of each other except for the float bowl area. Maybe some kind of junk has found its way into both idle circuits. Since the accelerator pump on that side pumps gas the float bowl area must be OK.

You may not be able to just switch carbs from one side to the other as the linkage will then be all screwed up. And the fuel inlets will be pointing the wrong way. But if you can do it, I would, even without hooking up the linkage. I would get the car warmed up then switch them fast, as the car may be hard to start without the linkage, since you cant pump the gas.
See if the problem follows the carb.

But actually, before that, it occurs to me that you could have a huge air leak at the base of the manifold on that side. Its easy to get the manifold to incorrectly sit on top of the tin. You tighten it down and you still have a leak. Could affect both barrels on that one side.

I'd still check compression. Just be really careful that you dont cross thread the tester (if its the screw in type, which ideally it would be) when screwing it into the spark plug threads. You cant see what you are doingand you have to rely on your knowledge of the angle that the spark plug are at when they are thereaded in as normal. It a pain an dmay not show the problem in the end, but it is very useful info.

BTW, before all of this, what do the tips of the sparkplugs look like? Should be light tan. Are the ones form the bad cylanders black or all wet?

If they are all wet then, at least basically, your gettin fuel down where it needs to be.

How do they compare to the "good" cylanders?

Plugs can tell the whole story.

Good luck and let us know.

Curt

[GBG1000]

Curt,

I hope you are correct about manifold leak. It would probably be the least expensive thing to correct.

I switched the carbs and the passenger side is still unresposive. That seems to indicate to me that the (main) problem is not the carb.

With my hand, and later with a thin strip of cloth, I notice that there is air blowing out from somewhere, near the # 3 manifold riser. It is not hot air. I can't pinpoint the exact location but strangely, it seems strongest near the middle of the riser.

I would have expected a vacuum, not pressure.

What do you think is going on here? Should I pull the intake manifold? Is it completely accessible from the top? Is tere any potential for a novice (me) to be opening a can of worms here?

Thanks in advance for the advice.

[GBG1000]

Well I removed inspected and replaced intake manifold. I had High hopes because the nuts were just snug. Tightening it down did nothing.

The blowing air phenomenon was traced back to an opening in the tin.

My next step, as soon as I get a bit of time, will be to check compression and valve clearances.

[Curt914]

OK, you certainly are getting down the list and making progress.

So its not the carbs, its not the intake manifold.

That leaves compression and ignition.

I re-read your first post and the fact that the car ran OK (just OK) and then suddenly a lot worse needs to be kept in mind as you go through this.
Kinda like, something failed suddenly.

What do the plugs look like?

Have you looked at the inside of the distributor cap? Is there something weird about the way it looks in there? With a good light, look around the posts for the the two bad cylinders. Looks for cracks and arching. I know you are getting a spark at all the plugs, but still there could be something funky going on (spark wise) when the plugs are inserted into a running engine. Are you testing for spark by watching for a spark at the end of the actual spark plug (across the gap) or by somehow watching the spark leap from the end of the spark plug wire (without the spark plug inserted)?

When you had the unisyn on those two cylinders, was there any flow indicated by the unisyn? Any at all? Even if the cylinder is not firing, if you have compression and no leaks anywhere (like the intake manifold), non firing cylinders would still draw air through the carb when the intake valve opens. At least I think thats right. So the unisys should show some flow.

No, its time for the compression test.

Go carefully here so that you can count on the results with certainty.

IF you get no compression, you want to make sure that its because there actually is no compression in the cylinder as opposed to there being no compression due to the test being done wrong. If there is no compression, then your talking about taking the head off, and you don't want to go down that path for no actual reason.

Good luck and let us know what you find.

Curt

[Brother]

fuel delivery could be an issue. The two previous owners were delinquents who only drove the car 2,000 miles in 3+ years. Cleaning out or rebuilding the carbs could help with fuel delivery and air/fuel mixture. Can you kill the car by plugging the carbs?

The wires and plugs were replaced last year.

[GBG1000]

New Data-
Compression test (Cold wide open throttle)
1-4 = 100, 100, 98, 105

Plugs-
1,brn-bk, dry light soot
2, v blk and sooty, dry
3, v blk and sooty, dry
4, brn-blk no soot, moist with gasoline odor.

Cleaned & replaced plugs.
Wire brushed contacts inside dist cap. and rotor
Cleaned/brushed male end of wires that plug into dist cap, also expanded them a bit so they would be more snug.

Started the car and could immediately tell it was running differently.

New observations
Idle mix screw adjustments on passenger and drivers side carbs now have an effect.
CHTs are equal on both sides at idle (170). (Sensors are on #1 and #3)
However when I drive it, the drivers side gets much hotter (250 vs 175).
When I experiment with unisync, it tends to want to choke the drivers side barrels (slows, spits, backfires and would ultimately stall if I don't remove it).

When I put the unisync on either barrel of the passenger side carb, it does not seem to affect the idle.

Ok- I am happy to have good compression, also happy to see passenger side carb respond.
I know I have carb work to do, if for no other reason than to get both accellerator pumps to behave the same.

Since I now know that ignition is part of my problem, I am going to check the timing.

I will also, when time permits check/adjust the valves. The PO is helping me out a lot with the history, and informed me that due to the aftermarket cam (a "262" cam), my clearances shout be set at 0.004. Can I get any informed second opinions on that?

I suspect vacuum leak in the passenger side carb, because it doesn't choke out with the unisync. will a rebuild kit be liekely to fix this?

Hopefully, once I complete all of these things I'll be back in business again.

I f there is anyone that can recommend a good reasonable mechanic in Jacksonville, I may also think about that shortcut to getting back on the road.

Please keep the opinions and advice coming.

Thanks- Jerry

[Brother]

I would do or get a valve job done first because if a valve is slightly open, everything else could change on you. It might support the different temp, but I seriously suspect the sensor wire. Not the yellow part but the brown part that has the ring terminal on it. Sometimes it used to be stuck down at 170 like it never warmed up and then spring up to 250-315 like the other side and every so often jump down.

[Curt914]

Hey, that’s great news. Progress is made.

To keep the ideas and opinions coming, here’s a few

Next chance you get, get a new distributor cap and rotor. And a new set of plugs. And so, what kind of distributor do you have? That’s a big topic around here. Let us know. Which one you have can have a big impact on the way the car ultimately runs, or so I’m told.

Onto the carbs. So much to say with regards to rebuilding, which is what I assume you’ll do soon from your last post. Its really easy actually, just gotta pay attention to the details.

There’s the rebuilding of the carbs and then there’s tuning them. What you do during the rebuild phase can make the tuning part easier.

If you are going to tear them apart, note the following:

Write down what all the brass jet sizes are. To get the car running correctly, you need to know what the idle jet, main jet, air correction and all the other brass jet sizes are and report back here.

Also check the idle jet seats. One of my carbs came with a cracked idle jet seat, which is a brass part and is not removable. Someone in the past screwed down the mixture needle too far and cracked the seat. It took me a long time to find that one and was very frustrating. Srews up the carb completely.

If you are going to clean the carbs, I am told not to soak them in carb cleaner too long, a few hours and that’s it. Supposedly the cleaner can have an effect on the body of the carb. Compressed air is your friend, of course.

If you remove or fiddle with the throttle plates, make sure and tighten down those screws that hold them in. Last thing you need is for one of them to come loose and to find its way into your motor. I put my carbs back in place once and was not dead sure they were really tight. Not a good thought as Im driving down the road.

Take a good look at the condition of the levers on the end of the carb that actuate the throttle plates. They must be free and with no slop due to wear. I put all new ones on from CB performance. I also bought all the links and heim joints that connect up those throttle levers to the crossbar linkage. It’s impossible to balance the carbs if those parts are worn out or sloppy.

CB performance is one place that has all the rebuilding parts you might need. Sounds like you will need to look at the accelerator pump area of your carbs in addition to the basic stuff.

Before you put your sparkling clean and newly rebuilt carbs back on the engine, do the basic setup. All air bypass screws closed. Do your carbs have vacuum advance ports? Some do. Make sure they are closed. Set all four mixture screws out one turn from lightly seated. Set the speed screw one quarter turn in after it contacts the arm. This is much easier to do when the carb is sitting in your hands. Now take a look the throttle plates.

I had one barrel where the throttle plate uncovered one of the progression ports. Those are those tiny holes right where the throttle plate touches the barrel when its closed.

For idle adjustment, those holes are supposed to be covered. If they are exposed during initial idle mixture adjustment, your not gonna get it right. Redline talks about it I think.

So I readjusted my plates and reset the speed screw again at one quarter turn out. I would have never seen that if the carbs were already on the car.

Oh yeah, something I discovered last night. With the carbs all reassembled but not yet on the car I noticed something odd. One of the carbs (that does not respond to idle adjustment too well), its float was kinda stuck. New float and all, but when I turned the other carb over, you could hear the float drop. Flip it back over and you could hear it go the other way. Not so with the ”bad” carb. Flip it on its back, and you had to shake the carb a bit to make the float drop. Back the other way and again it would not drop. It just was not entirely free. So I looked at the float and it was a bit tweaked. Straightened it out and now its free. Theres not much room in there. Maybe the float would have raised with fuel in the bowl, maybe not. Not takin chances.

Did I mention float height? This is an absolute must. So much has been written about setting floats and that if you have it wrong, you will never get the car to run right. Spec from Weber is 10 mm, but I have heard 11 or 12mm is what is actually recommended. I set mine to 11mm with the paper gasket in place.

I used a set of calipers as shown in the Harney tech article listed below. If you don’t have a set of calipers you can use a drill and lay it on its side to make the measurement. I think a 15/32 drill is roughly 12mm. Double check me on that.

OK, here is a good website with rebuild info.

Harney’s cab clinic for IDF’s. This guy knows what he is doing.

http://www.carburetorclinic.com/tech_articles.htm

Weber dual carb rebuild, may be hard to read s it’s a scan of an article. Its worth it though. From CB Performance – lots of Weber parts

http://www.cbperformance.com/Feb2002.asp


Here is another CB Performance article on rebuilding Weber IDA’s, good info s they are related to IDF’s

http://www.cbperformance.com/Apr2006a.asp

Weber dual carb rebuild, may be hard to read. From CB Performance – lots of Weber parts

http://www.cbperformance.com/Feb2002.asp


Well, have fun! Oh yeah, what size engine do you have? Is it a 1.7 or 2.0?

Curt

[SGB]

first, I'll admit that I scanned the responses, so I may be bringing up a known issue. It is possible (even likely) that one of the throttle linkage arms that stick out from the crossbar has slipped along the bar so that the actuation of the carbs is not equivilent. It really sounds like an "out-of-balance" problem to me, but all the precursers have to be looked at first- valve adjust, timing, and plug cleanliness. If you rebuild the carbs, make sure you set the float level carefully, but be aware that loading the press fit "shaft" that the float attaches to can cuase the shaft attachment ears to break off. Both of my carbs have this problem fixed with JB weld.

[GBG1000]

Thanks for the input Scott & Curt. My time will be scarce for a couple of weeks, but I'll post any developments.

[GBG1000]

I imported my mechanic (brother) from Cincinnati. We put new rebuild kits in the Carbs, and cleaned them out (some crud and emulsified water/fuel). The Floats also seemed to need quite a bit of adjustment.

At the moment of truth, the results were great! She runs like never before since recent purchase. I couldn't believe that carb issues could make the car run so bad.

It now responds great at all throttle positions. I am loving this car again.

Thanks to all who offered help.

[Brother]

Fantastic. I'm glad everything is working better now.