Weber carburetor balancing

gdimassa · #1 (**permalink**) 06-19-2008, 07:22 AM

Hi
I have finally builded my differential oil vacuometer and as I suspect my webers arent balanced...
I see that there is a screw to balance the front carburetor with respect of the front one... but how to balance each butterfly? My carbs hasnt the bypass screw.

FreeLSD · #2 (**permalink**) 06-19-2008, 02:07 PM

It should have. Blanked, maybe.
What carb model do you have?
If DCOE -
http://webers.ru/docs/weber/schematics/40DCOE151.pdf
part number 26.

gdimassa · #3 (**permalink**) 06-20-2008, 03:05 AM

Thanks I have fonded it!!!
it was blanked wit some thing like a red paint. But I am able to screw only the left one??? I will post a photo...

FreeLSD · #4 (**permalink**) 06-21-2008, 11:17 AM

Still no carb model specified.
Adjastent butterflies may have been balanced at factory, no need to rotate those screws. Measure vacuum at first.

gdimassa · #5 (**permalink**) 06-25-2008, 04:51 AM

Sorry for the lag...
So Carbs are 40DCOE 106(rear one) 40DCOE 107 (front one)

FreeLSD · #6 (**permalink**) 06-25-2008, 07:43 AM

Air bypass screws are normally closed. Only difference in flow between adjastent barrels may require rotating out the screw in cylinder, which have less airflow. So you have to measure vacuum difference in each single carb and make a decision - if it's worth dealing with those screws.

gdimassa · #7 (**permalink**) 06-25-2008, 07:59 AM

I cant find anywhere the acceptable balancing tolerance ? for example a difference of 0,43 inch-mercury could be acceptable? or I need to dealing with the bypass screws?
Thanks

FreeLSD · #8 (**permalink**) 06-25-2008, 01:14 PM

Balance should be as close as possible. I don't know your synchrometer type, so 0.43 sound very relative. Check if that difference stays in more throttle opening - when you open throttles further, to 2-4kRPM. If difference goes - just ignore it and try to setup idle with what you have.

Alfacliff · #9 (**permalink**) 06-25-2008, 01:16 PM

adjust the spring loaded coupling between the carbs for best balance above idle. then use the air adjust scrrews for smoothest idle. should get the job done.
cliff

FreeLSD · #10 (**permalink**) 06-25-2008, 10:31 PM

Quote:

Originally Posted by Alfacliff

adjust the spring loaded coupling between the carbs for best balance above idle. then use the air adjust scrrews for smoothest idle. should get the job done.
cliff

**1,6 HF** · #11 (**permalink**) 06-25-2008, 11:33 PM

Quote:

Originally Posted by FreeLSD

Hello cliff! Author is speaking of single carb imbalance, the difference is between single carb chokes.

FreeLSD · #12 (**permalink**) 06-26-2008, 04:42 AM

Right, 1.6HF. I'd do the same. But author said that air bypass screws are stuck and not rotating.

By the way I've heard what idle mixture screws changes balance itself, by allowing more air/fuel mixture to the single barrel. That's why it's recommended to keep each screw setting as close as possible to others.

Alfacliff · #13 (**permalink**) 06-26-2008, 05:06 AM

the reason for abllancing the throttle plates first is because if it is off, and you balance the air bleed screws at idle, then the throttle plates, it throws off idle. thats just my thoughts.
cliff

FreeLSD · #14 (**permalink**) 06-26-2008, 11:32 AM

I didn't get it cliff.
Do you mean that at first we synchronize maximum airflow barrels on both carbs, then allowing more air to weak barrels with air bleed screws?
Please, explain why, I can't see the logic, but sure that your experience really interesting.
Thank you.

Alfacliff · #15 (**permalink**) 06-26-2008, 11:35 AM

if you synch the carbs at a rpm above the idle circuits, the bleed screws have no effect. then adjust the bleed screws for ballance at idle speed. the bleed screws are supposed to affect the idle circuit only. if the throttle synch is off and is compensated for with the bleed screws, then speeds above idle wont be very synched.
cliff