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Jazz86

Triple OER/SK carb issues, not balancing (SOLVED)

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I have been having issues with my OER SK 40mm carbs. The problem is very elusive and I have not been able to find the source. I will do my best to describe the problem and I am willing to clarify if needed. I am going to refer to carb(#1) as cylinders 1 and 2.

Carbs #1 and #3 are perfectly fine, it is carb #2 that is acting up. I started to sync the carbs, first by disconnecting all the linkages. I managed to balance #1 and #3 using an unisyn tool. However, #2 (cylinders 3 and 4) would be run leaner than the others. I unscrewed the idle mixture screws for #2 a few turns, and it leaned out even more resulting in popping out the carb and a nearly white spark plug. Also the #2 would draw a lot more vacuum than #1 and #3, and I unscrewed the idle speed screw for #2 and #2 still ended up drawing a lot more vacuum. #2 has enough vacuum that when I touch the unisync tool on #2 the engine will nearly die and then fuel spills out and then rpm picks up a lot. However, I got the car to idle smooth enough by tuning by ear and I would hold rpm at 2.5k and 3k and the #2 carb would cough and the exhaust would back fire, checking the plugs (cylinder 3,4) they were even whiter than at idle. Meanwhile the other plugs were a nice brown. This issue has bee driving me mad.

Issues list:

1. carb #2 runs lean

2. (all linkages disconnected)(speed screw backed off 100% for #2) carb #2 still draws more vacuum that #1 and #3

3. Carb #2, touched unisycn tool the engine nearly dies, fuel drips out of throat, engine speed rises rapidly

4. #2 meaning cyl3,4 mixture screw(1 turn), nearly white plug, all others are a nice tan

5. #2 mixture screw(2 turns), completely white plug, all others are a nice tan

6. rpms held at 2.5k and 3k carb #2 cough and exhaust back fire

7. rpms held at 2.5k and 3k carb #2 (plugs 3,4) are bone white, all others are a nice brown

8. no binding in the linkages, linkages move very smoothly

9. Sprayed carb cleaner on all joints and seals, no increase in rpm

10. float levels all set to the same factory settings

 

received_292849727880960.jpeg

Edited by Jazz86

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4 hours ago, 240260280 said:

Are fuel levels the same?

Are any gaskets leaking?

What are jet sizes in each carb?

I checked the fuel levels for #2, they seem to be okay but I will compare them to #1 and #3 when I get the chance.

As for a gasket leak, the obvious places like; manifold to head, and carb to manifold are all in good order. Though I suspect a leaking shaft seal.

Jetting weber drilled: 140 main, F11 emulsion, idle 50F9, pump 45

Here is a pic of the fuel in carb #2 right after idling for 5 mins. Looks kinda dtiry because of the lighting. I did clean out a few grains of dust after taking the photo.

 

20171022_104638.jpg

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I really liked the gas line routing.  I was planning on copying it actually, I like the idea of a return line to the tank.  What fuel pump are you using?  Stock?  Electric? Both? I like the idea of using stock fuel lines.  You might try plugging the return to see if it pushes fuel into each better?  

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7 minutes ago, duffymahoney said:

I really liked the gas line routing.  I was planning on copying it actually, I like the idea of a return line to the tank.  What fuel pump are you using?  Stock?  Electric? Both? I like the idea of using stock fuel lines.  You might try plugging the return to see if it pushes fuel into each better?  

I'm  using the stock fuel rail, as it also acts as a built in fuel regulator. As for fuel pumps, I am running two pumps in series. It goes in this order 

Tank>>>electric clicker pump>>>stock pump>>>carbs

Its a crude system but it worked great for my old SUs and DGVs, never fuel starved even at extended periods of WOT.

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Could there be any throttle plate issues on carb #2?  Maybe the plates are not aligned and one is letting in more air than the other.  I noticed a big imbalance on one of my Weber DCOE carbs when I replaced one of the throttle plates due to damage.  The other plate let in more air due to leaking.  Replaced other plate with a new one, problem solved.

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6 minutes ago, duffman said:

Could there be any throttle plate issues on carb #2?  Maybe the plates are not aligned and one is letting in more air than the other.  I noticed a big imbalance on one of my Weber DCOE carbs when I replaced one of the throttle plates due to damage.  The other plate let in more air due to leaking.  Replaced other plate with a new one, problem solved.

I suspected the plates or the shafts as well. I did not know that the plates might not seal well. That is something to look into for sure. The thing that puzzles me is that this air flow imbalance is across both barrels of #2. But if they are bad I hope weber dcoe plates will fit these OERs.

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How does the fuel level in carb 2 compare against the other two when you remove the lid.

 

Also does the fuel needle valve work properly in #2?

 

If it is not a fuel issue causing the lean cylinders then maybe it is valves.

 

 

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5 minutes ago, 240260280 said:

How does the fuel level in carb 2 compare against the other two when you remove the lid.

 

Also does the fuel needle valve work properly in #2?

 

If it is not a fuel issue causing the lean cylinders then maybe it is valves.

 

 

#2 seems to be a touch lower than #1 and #3.I will raise the float level. The needle valve looks clean and it moves up and down smoothly, but how do I check for clogs in a needle valve?

Woud a lean condition also pull more vacuum as opposed to a simply rich mixture?

I did do the valve adjustment a week ago before putting on the carbs, and the valve clearances are in check. 

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2 minutes ago, duffymahoney said:

Could you swap 1 and 2. That will show you for sure if it’s float or needle?

I will do that next time. Going to take apart carb #2 as well when it's off and report my findings.

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I'd like to add that my lean condition on cylinders 3 and 4 are mainly caused by the #2 carb sucking in too much air through the throat. Since the vacuum can be read on the Unisync for a split second. It reads off the scale. Meanwhile the same unisync on carbs #1 and #3 read perfectly in the middle. I also checked how far open my butterfly valves are open on all the carbs through the progression holes and they are all in the same place. 

Edited by Jazz86

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fuel flow check:

Just hold the lid to your face and blow air through the fuel entrance in the lid.  Open and close the needle valve by moving the float and you should hear the air stop and start when the valve opens and closes.

 

Balancing:

Too much vacuum on one carb at idle means it is doing all the work and the other two are not.  You need to close the throttle valve stops on all to be the same before you start balancing.  Also ensure the idle enrichment screws are all backed out by the same amount at start.   Do not turn any enrichment screws until the air is first balanced.

 

Here are the steps to follow:

 

1. Gently turn all 6 idle enrichment screws in until they stop then back each out 1 full turn (note: some recommend anywhere between 1.5 turns to 2.5turns however the SK Carb manual recommends between 3/4 to 1 full turn so 1 full turn should do)

2. Disconnect push rods from carb arms.

3. Turn back all 3 idle stop screws until  each is not touching the idle stop.  Then turn each in until it just kisses the stop, then give each an additional 2 turns to open the throttles a crack.

4. Start the engine and let it warm up for 10 min until it is nice and hot. (Don't worry about rpms unless they are too low).

5. Measure the air flow into each carb and adjust the idle stop screws until you get the air balanced AND such that you have lowered the rpms to between 650 and 850rpms.

Hopefully this will get you in the ball park before you have to mess with the enrichment screws and linkage.

 

 

Edited by 240260280
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First dump the unisync. It does nothing but choke down the carbs. Spend the money and get a syncrometer. No choke down at all. Second what is you fuel pressure feeding your fuel? Third. Not only is your temp warm but bring your oil temp to a min of 180 before you turn your carbs. Last what is your AFR at once warmed at idle? You can always move carb #2 to either the first or third position and see if the problem moves with you. All in my opinion of course


Sent from my iPhone using Classic Zcar Club mobile

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5 hours ago, 240260280 said:

fuel flow check:

Just hold the lid to your face and blow air through the fuel entrance in the lid.  Open and close the needle valve by moving the float and you should hear the air stop and start when the valve opens and closes.

 

Balancing:

Too much vacuum on one carb at idle means it is doing all the work and the other two are not.  You need to close the throttle valve stops on all to be the same before you start balancing.  Also ensure the idle enrichment screws are all backed out by the same amount at start.   Do not turn any enrichment screws until the air is first balanced.

 

Here are the steps to follow:

 

1. Gently turn all 6 idle enrichment screws in until they stop then back each out 1 full turn (note: some recommend anywhere between 1.5 turns to 2.5turns however the SK Carb manual recommends between 3/4 to 1 full turn so 1 full turn should do)

2. Disconnect push rods from carb arms.

3. Turn back all 3 idle stop screws until  each is not touching the idle stop.  Then turn each in until it just kisses the stop, then give each an additional 2 turns to open the throttles a crack.

4. Start the engine and let it warm up for 10 min until it is nice and hot. (Don't worry about rpms unless they are too low).

5. Measure the air flow into each carb and adjust the idle stop screws until you get the air balanced AND such that you have lowered the rpms to between 650 and 850rpms.

Hopefully this will get you in the ball park before you have to mess with the enrichment screws and linkage.

 

 

Thanks, I have already tried the mikuni and weber baseline settings as I am no stranger to triple webers but this problem is something that confuses me and my fellow triple carb friends.

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24 minutes ago, Travel'n Man said:

First dump the unisync. It does nothing but choke down the carbs. Spend the money and get a syncrometer. No choke down at all. Second what is you fuel pressure feeding your fuel? Third. Not only is your temp warm but bring your oil temp to a min of 180 before you turn your carbs. Last what is your AFR at once warmed at idle? You can always move carb #2 to either the first or third position and see if the problem moves with you. All in my opinion of course


Sent from my iPhone using Classic Zcar Club mobile

Fuel pressure is at a stock 3.5-4psi since I am running the stock mechanical pump and an electrical primer pump. And yes, the car is all warmed before I tried to tune it, it's common knowledge. As for afr, there is no way to get an O2 sensor on all exhaust runners, I can only tell via spark plug (rich or lean). And yes I couldn't agree more, moving it will help me tell if its the carb alone.

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Maybe the throttle rod in carb #2 is twisted.

Did you look in progression holes to see where throttle plates come to rest in the throat with the stop screws back off all the way? Compare all 6.

Carb two is not closing enough.

Edited by 240260280

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Just now, 240260280 said:

Maybe the throttle rod in carb #2 is twisted.

Did you look in progression holes to see where throttle plates come to rest in the throat with the stop screws back off all the way?

Yup, That was one of the things I looked into. The progression holes are #2 carb exactly the same as #1 and #3. However, that is with #1 and #3 turned about 1 turn, and they are synced perfectly. The #2 carb with the screw just making contact the progression holes match the #1 and #3

So the butterfly valves are all in the same place in relation to the progression holes; just barely exposing the edge of the first hole. 

CARB 1 :1 turn      progression holes exposed the same amount but different turns

CARB 2 :0 turns

CARB 3 : 1 turn

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7 minutes ago, 240260280 said:

OK then it is probably the rare case where the cold start circuit is not sealing on carb #2. Check it out.

Yes, that is exaclty what one of my freinds just suggested!!! How do I go about checking that for leaks. I believe it has to do with plunger near the choke?

5 minutes ago, 240260280 said:

btw the vacuum ports for tuning are not leaking or opened?

Yes, the vacuum ports all have a rubber cap and I sprayed carb cleaner on them to double check.

Thanks again for giving my issue so much thought.

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