I agree with Randall. There is normally some black buildup of gasoline and
engine vapors on the inside of the dashpot. Those have to be removed for
the piston to freely move up and down. But if any material is removed it
will create a space for air to bypass the piston and reduce the venturi
effect needed for the carb to operate properly. If you look at the wide
edge of the piston it has some grooves on it to enhance the boundary effect.
Pete
-----Original Message-----
From: owner-triumphs@Autox.Team.Net
[mailto:owner-triumphs@Autox.Team.Net]On Behalf Of Randall
Sent: Friday, December 17, 2004 5:48 PM
To: triumphs@Autox.Team.Net
Subject: RE: SU Rebuild
> At 21:16 -0800 16/12/04, JOSEPH MATO wrote:
> >The thing that seems to work for me is to polish the hell out of the
> >dashpot interior and carb body with steel wool or scotch pads to
> >remove aluminum corrosion and make it smooth as a babys bottom.
I'm going to disagree here about polishing the inside of the dashpot. The
surface is supposed to be strictly non-contact, so polishing adds nothing to
the performance of the carb. However, it may worsen the precision fit
between the piston and the dome, leading to sloppy mixture control.
Polishing the intake bore has also been shown to be counter-productive, a
slightly rough surface actually flows better due to boundary effects.
So, polish the outside to your heart's content, but the only area inside
that should be polished is the outer surface of the jet, where it slides
through the seals. This will extend seal life and may be necessary for
proper choke operation (as it appears that replacement jets are not being
properly finished by the manufacturer).
Randall
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