No response to idle mix DCOE 40s - what would you try next?

[Golfcar]

13 minutes ago, Hans said:

And the coil springs.

 

Errrrr, actually carb to manifiold but yes, they can be trouble. Some folks swear by them. I swear at them. 

Oops. Hans is correct. 

I removed mine too. 

 

[man_mark_7]

57 minutes ago, Hans said:

Are these Italian DCOEs/ Are you using soft mount gaskets?? Do you have the little washer cups and O-rings on the mixture screws?

Thx for your questions. Yes, they are Italian 151 DCOE's. I am not using the soft mount gaskets. I'm using the relatively thin gaskets provided with the IE manifold.

 

Ah-ha!! No washer cups and o-rings on the mixture screws. I never noticed them in this part diagram before. Items 44&46, correct? The definitely didn't come with the carbs. I'll get some on order. I'm surprised thoughT the threaded lengths of the needle valves are so long it seem unlikely there would be any air leaks in this area - but I'm sure they didn't just throw them in for looks.

 

It's hard to tell from the image - do they sit deep in the bore in the carb or do they ride on the top surface of the carb just underneath the spring?

 

thx

mm

 

[Son of Marty]

I'm pretty sure that Hans was referring to the washers/springs and o rings used with the anti vibration mounts. If your not running them good IMHO. I haven't seen every car that runs dcoe's but I have seen more than a few and I've seen a car that runs soft mounts from the factory.

[Hans]

17 minutes ago, Son of Marty said:

I'm pretty sure that Hans was referring to the washers/springs and o rings used with the anti vibration mounts. If your not running them good IMHO. I haven't seen every car that runs dcoe's but I have seen more than a few and I've seen a car that runs soft mounts from the factory.

Hans was referring to items 44, 46 and 47 in the diagram. As suggested, probably not there for decoration. If we're looking for an air leak, that's a possible source. Now why the other three barrels are happy I can't say.

I've not tried running without them so can't say what difference they make. They sit on top

Those soft mount springs etc are another reason I dislike them from my limited experience.

Edited September 29, 2020 by Hans
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[Son of Marty]

Sorry Hans, I need to learn to read  s  l  o  w  e  r and work on my comp ray hention.

Edited September 29, 2020 by Son of Marty

[Hans]

25 minutes ago, Son of Marty said:

Sorry Hans, I need to learn to read  s  l  o  w  e  r and work on my comp ray hention.

Apropos of nothing,  have you been to the Patton museum east of palm springs?

Now, OP, have you tried blasting  that hole with carb cleaner (wearing safety goggles)?

Edited September 29, 2020 by Hans
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[Son of Marty]

Going this March if the new abnormal is over by then.

[Golfcar]

1 hour ago, man_mark_7 said:

Thx for your questions. Yes, they are Italian 151 DCOE's. I am not using the soft mount gaskets. I'm using the relatively thin gaskets provided with the IE manifold.

 

Ah-ha!! No washer cups and o-rings on the mixture screws. I never noticed them in this part diagram before. Items 44&46, correct? The definitely didn't come with the carbs. I'll get some on order. I'm surprised thoughT the threaded lengths of the needle valves are so long it seem unlikely there would be any air leaks in this area - but I'm sure they didn't just throw them in for looks.

 

It's hard to tell from the image - do they sit deep in the bore in the carb or do they ride on the top surface of the carb just underneath the spring?

 

thx

mm

 

Be careful. There are two styles of Idle adjustment screws. The long pointed ones are in the 151 carbs. Idle settings for these are different. Usually more turns out as the screw is very tapered. Many books are referring to the old style screws which the base setting was 2-2.5.

If these are 151's then you have the bypass screws. 

Basically you use a synchrometer tool to get the flow for each carb the same. The number of the reading is only a reference. 

Make sure the bypass screws are screwed in snug. 

Take a reading with the air sync tool and see which throat flows the most air. Say a 5 on the gauge but the other throat is a 4.25. 

When that is determined then you open the bypass screw of which ever throat was the lowest until it matches the other throat. 

So only one screw is moved. This balances the throats which makes balancing the two carbs much easier. I have three to do on my 6 cyl M30 motor. This may still not be your problem but will really help balance the two carbs so that when you do make throttle changes they are synced.  

[Son of Marty]

151 is the Weber code for a non specific dcoe, so while not set specifically for a bmw they are set up for any car that could run that size dcoe, they can be set up to run well on a 2002 but probably not as well off idle as the matched set of 15/16 carbs that have the progression holes drilled for the m10-m30 engine, but I'm splitting hairs here. If your high idle doesn't respond to timing I had one set of webers where the throttle arm was hitting the little idle stop on the carb body that the speed screw goes through just a bit and the car wouldn't idle below 1200-1300 rpm, worth a look anyway.   

[Hans]

In reviewing the original post, I'm wondering about the bit about needing to push the linkage back. That might indicate some butterfly alignment issue, or perhaps just linkage. OP, are you using a squirrel cage sync?  And the values are all the same?

[Hans]

4 hours ago, Son of Marty said:

Going this March if the new abnormal is over by then.

There's a good one in Luxembourg too, but might as well be on the moon.

[man_mark_7]

11 hours ago, m5bb said:

Be careful. There are two styles of Idle adjustment screws. The long pointed ones are in the 151 carbs. Idle settings for these are different. Usually more turns out as the screw is very tapered. Many books are referring to the old style screws which the base setting was 2-2.5.

If these are 151's then you have the bypass screws. 

Basically you use a synchrometer tool to get the flow for each carb the same. The number of the reading is only a reference. 

Make sure the bypass screws are screwed in snug. 

Take a reading with the air sync tool and see which throat flows the most air. Say a 5 on the gauge but the other throat is a 4.25. 

When that is determined then you open the bypass screw of which ever throat was the lowest until it matches the other throat. 

So only one screw is moved. This balances the throats which makes balancing the two carbs much easier. I have three to do on my 6 cyl M30 motor. This may still not be your problem but will really help balance the two carbs so that when you do make throttle changes they are synced.  

Thanks!!

The idle screws look pretty long and pointy to me. I have started with them about 2 turns out, but I don't know that it matters much since I turn them in until engine starts to stumble then back them out until I don't notice any improvement. I think I've been ending up at a bit over 2 turns out for the three of them that seem to be having an effect.

 

Air sync looks great across all 4 bores. I have adjusted one balance screw on each carb just as you said.

 

 

[man_mark_7]

7 hours ago, Hans said:

In reviewing the original post, I'm wondering about the bit about needing to push the linkage back. That might indicate some butterfly alignment issue, or perhaps just linkage. OP, are you using a squirrel cage sync?  And the values are all the same?

Yes, using an SK(?) sync. All the bores read just a hair over 5 at about 1300RPM.

[Hans]

Will it idle below 1300? If memory serves, I usually check this at idle.

Edited September 29, 2020 by Hans
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[Hans]

https://cnx.org/contents/oKbaEWQ3@2/Selection-and-Tuning-of-Weber-DCOE-Carburetors

 

 

Have a look at this.