[Roadsters] Carb tuning

[Keith0alan at aol.com]

When the piston is sitting where it wants to be for the engine load  
condition the mixture is correct. When it's forced low the mixture will be rich.  When 
forced high the mixture will be lean. On acceleration you need to run a  
richer mixture for a short time. If the piston is allowed to move freely the  
mixture will remain correct for constant speed running but it will be too lean  
for acceleration. The dash pot oil damps the rise of the piston forcing it to be 
 temporarily lower than the steady state level. This enrichens the mixture 
for  acceleration. The speed of rise and thus the amount of enrichening can be 
varied  with the weight of the dash pot oil. Too thin or missing and you go 
lean and  stumble. Too thick and you go too rich and have a boggy, soft 
acceleration. Just  right and you have a crisp acceleration. The factory oil is about a 
10w, the  same as ATF. You want the thinnest oil that controls the stumbling. 
Motorcycle  fork oil comes in a number of weights and in convenient screw top 
bottles. A  medical syringe available at the feed and seed store with a short 
piece of  vacuum line is ideal for changing dash pot oil.
 
How's that?
 
keith

 
In a message dated 7/27/2008 8:42:12 AM Pacific Daylight Time,  
9laser3 at bright.net writes:

Keith,

For those of us that are still technically  challenged, ... can you break
that down for us?   (:-)

Paul

-----Original Message-----
Subject: Re: [Roadsters]  Carb tuning

What he said.

keith


In a message dated  7/26/2008 11:56:52 P.M. Pacific Daylight Time,  
sandhoff at csus.edu  writes:

>  when I punch the motor at low rpm's the motor gasps  for air and
>  several backfire pops occur

Sounds like  there's no oil in the dashpots.  Unscrew those little
black plastic  caps on top of the domes. Lift the rods  out, and drop
them back in.  They shouldn't just drop down - they should  'squish'
thru a tiny pool  of oil. Add 20W, a splash of engine oil  (10w-30),
some Marvel Mystery  Oil, or some ATF (any brand auto trans  fluid).
Takes only a couple of  tablespoons or so.

-- John
John F Sandhoff sandhoff at csus.edu   Sacramento,  CA







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