<VV> Carb woes

[Larry Forman]

At 12:08 PM 9/11/2004 -0400, Bill Elliott wrote:
>This is embarassing, but I'm having my first carb issue in years.
>
>Bought a set of rebuilt carbs and have never been able to get them set up 
>right.  I'm convinced the issue
>is a vacuum leak on one of the carbs. When I hold my hand flat over the 
>carb, the idle speeds up.
>
>Thanks!
>Bill Elliott

Hi Bill,
Here is what I did to find a pesky leak like that.  Realizing that oddity 
when the top was covered, I placed a plastic baggy with rubber bands firmly 
over the top of the offending carb and then fired it up.  Now I could use a 
rubber hose with one end held to my ear to "sniff" for the air leak.  I 
found that there was a leak in the top of the carb where the horizontal 
hole is for the top cover bolt down "J" bolt.  It seems that there is a 
difference in the internal porting between the Late and Early carb 
tops.  If you try to convert a Late to an Early by drilling the horizontal 
hole for the J-bolt, it runs into an internal air vent and causes a 
leak.  Try searching around the top of the air horn when the air horn is 
sealed.

You could also have a leak by the balance tube.  This is quite common, 
since that area gets quite hot and hardens up the rubber tubes.  I like to 
replace these and use four hose clamps total.   Alternatively, I think 
there are now available silicone hoses which are much more durable in the 
high temperatures.

After checking these out, try swapping the carbs and ensure the problem 
moves with the carb.  That would isolate things like a cracked carb base 
insulator, which should be replaced with a new one, just because.

HTH,
Larry