Even a file is too aggressive and can't possibly get it round enough
Ideally it would be in a lathe but that is really hard to do
The best way to do it by hand is to chuck it into a drill press and spin it.
Then use fine sandpaper and remove brass in the desired area very gently. A
thousandth of an inch makes a big difference! You are likely looking for
around 0.005" removal.
I suspect that the mixture is a non-linear function of open cross section area.
As the space between the needle and the jet gets wider, I bet the flow gets a
lot easier. There could easily be issues of turbulent flow vs laminar flow as
the walls get further apart.
Nevertheless my first approximation assuming a linear function resulted in a
needle selection that seemed quite good for my engine.
-Tony
Sent from my 1837 Babbage Analytical Engine
> On Jun 7, 2019, at 2:00 PM, triumphs-request@autox.team.net wrote:
>
> Message: 4
> Date: Thu, 6 Jun 2019 13:57:42 -0700
> From: "Randall" <TR3driver@ca.rr.com>
> To: "'Greg Lemon'" <grglmn@gmail.com>
> Cc: <triumphs@autox.team.net>, "'Pete Arakelian'"
> <Arakelianp@mossmotors.com>
> Subject: Re: [TR] U.S. EPA Finalizes Rulemaking to Permit Year-Round
> Sales of E15 Gasoline
> Message-ID: <A977DEC0BB084269B41EE85B61224458@RYPC>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Those brass needles are really soft; I would suggest a fine tooth file and a
> light touch rather than a Dremel. I haven't worked out how big the flat
> should be, but it won't take much. You're only looking for something like
> 5% more fuel (or maybe 6%, depending on whose numbers you believe).
>
> Again assuming you want to run E15 in the first place.
>
> -- Randall
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