I need a tune

[AndyB]

My twin cam sounds a little like a traction engine on idle sort of a tut tut tut and when revved it runs on for a second or two which transfer into a couple loud backfires when you back out of the gas in 3rd gear. The throttle is not sticking, it returns to the idle position immediately. I used a syncrometer and have both carbs reading the same number.

Any ideas?

[James A]

When I owned a twin cam two different things did this to me and both were distributer related, vacuum advance issues and the other was the spring loaded rev limiter failing.

[twobone]

check that the choke/venturi has not turned within the carb

[AndyB]

check that the choke/venturi has not turned within the carb

 

Is that what they call the Auxiliary Venturi?

[twobone]

Its the venturi mentioned in this article:

 

http://tedperkins.com/weber_principles.htm

[AndyB]

Its the venturi mentioned in this article:

 

http://tedperkins.com/weber_principles.htm

 

Finally have time to try and sort my problem, first thing I noticed was the venturi mentioned in this article is loose. That's the tube inside the metal ring. If I stick my finger in there I detect slight movement whereas the other three are firm, no movement.

What I can't figure is what fastens this part?

Any help would be greatly appreciated.

[twobone]

There is a little grub screw on the side of the carb body that holds the venturi in place. If the venturi twists a bit in the body it can restrict the fuel flow (or so I have heard)

[AndyB]

No grub screws on this carb, mine are 40 DCOE 18 if that makes a difference. I'll keep Googling.

[twobone]

its item #28 on a regular DCOE

[AndyB]

OK I looked at the side and that's almost out of sight underneath with my setup, it will be a so n so to get to. I might have to use a bent screw driver. But if it solves my problem it will be worth it.

 

Thanks again

[AndyB]

No mine is held in with a piece of bent spring steel and after a further check they all have a little play so I'm back to step one