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

[Jazz86]

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

 

Edited October 28, 2017 by Jazz86

[240260280]

Are fuel levels the same?

Are any gaskets leaking?

What are jet sizes in each carb?

[240260280]

The fuel routing is a little unorthodox. Try running a rubber line directly from the pump to carb 1 and block after carb 3.

[ksechler]

I'd be inclined to think you're starving carb #2 of fuel.  I agree the fuel line routing is unusual.

[240260280]

Also check needle valve on carb #2 to make sure fuel delivery is not clogged or valve stuck.

[Jazz86]

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.

 

[duffymahoney]

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?  

[Jazz86]

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.

[Duffman]

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.

[Jazz86]

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.

[240260280]

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.

 

 

[Jazz86]

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.