Acceleration to Idle Question

[tittyman]

I have a BBC with a tunnel, dual 450'S, radical cam, 12:1...When I get off the throttle the engine wants to idle back down to around 2000 rpm for about 30 seconds before it finally idles back down completely to the curb idle speed of around 1200 rpm. My throttle plates close right away, I have a strong return carb spring on the throttle, my PV is 2.5. The boats accelerates very snappy without any bogs. This happens even if I am cruising at 2500-3000 rpm and let off the gas. What can I do to get it to idle right back down to its original setting without waiting for 30 seconds and why does that happen..thanks..

[GasGuzzler]

Try tapping the foot pedal real quick and see if it idles down. Sounds like the throttle cable may have a little bind or a rough spot in it and takes it a bit to relax with the spring tension. Better yet, unhook the cable and work the carb by hand and see if it sticks while running.

[tittyman]

Tried that..it's not in the cable or the spring..

[Taylorman]

Sounds like you centrifugal advance in your distributor is staying advanced. You may need to pull your distributor and lube it up a little. If the advance doesn't go back to the initial advance, your idle will stay high. Been there. I locked out the timing , cured that problem.

[tittyman]

I have a Don Zig mag..could that still be the problem..never had the mag apart..

[nyjetboat]

sorry to here your still having problems man. maybe your secondarys aren't fully closing check the arms and shafts ????

[SmokinLowriderSS]

Tunnel ram with 2 carbs.
Carb idle imbalance.
Exact same thing happens to both of my 4-carb motorcycles about every 2 years and when you hook up 4 vac gauges to the carbs, they are NOT identical, often several "hg apart. My bike tollerance is only 2mmhg.
Put 2 vac gauges on it, one on each carb and see what the difference is. If one pair of butterflies is only a hair more (or less) open than the other, the idle does exactly what you describe.

[tittyman]

So you think it's more of a carb issue rather than the weights in the mag might be a little dirty and sticking when it comes back to idle?
Second question..with a vertex mag how do you lock out the advance like one of the guys said to do..

[inwo]

Good info here.
Page down to inconsistant idle.
http://www.bob2000.com/carb.htm

[SmokinLowriderSS]

Second question..with a vertex mag how do you lock out the advance like one of the guys said to do..
If it isn't a drag boat, I fail to see one single valid reason to do it, other than to strain the starter harder and have to add things like an ignition cutout to let the starter get spinning before lighting the ignition.
Headaches, period.
Oh, and bragging rights to "locked out ignition advance".

[tittyman]

Lowriderss..I think your right about not locking it out after thinking about it...I do think it is the weights though..not the carbs..the mag is an older one and never been serviced..plus the boat had not been started in at least 5 years before I got it..the idle comes back about the same amount of time after I come off of throttle..not much veriation in time before it goes back to normal idle..the boat always idles fine once we get there....