[Roadsters] Carb tuning

[Paul]

  I was just kidding, but it's always great to hear some words of wisdom
from the slow SU guy!

 

Paul

 

From: Keith0alan at aol.com [mailto:Keith0alan at aol.com] 
Sent: Sunday, July 27, 2008 2:27 PM
To: 9laser3 at bright.net
Cc: datsun-roadsters at autox.team.net
Subject: Re: [Roadsters] Carb tuning

 

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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