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Re: [TR] SU questions

To: "list Triumph" <triumphs@autox.team.net>
Subject: Re: [TR] SU questions
From: "Jim Muller" <jimmuller@rcn.com>
Date: Sun, 01 Jul 2007 01:24:54 -0400
On 30 Jun 2007 at 18:43, Paul Dorsey wrote:

> Doesn't the SU Carb. dash pots/oil level/Carb dip sticks determine the carbs
> throttle reactions?  Especially under load?

The dashpot oil doesn't really affect operation under load.  It acts 
to slow down the piston reaction when you first open the throttle, 
but the piston then moves into place fairly quickly.  In other words, 
it acts as the accelerator pump in a conventional carb.  After the 
first second or so when you step on the loud pedal the piston has 
settled into its new postion.

> I think both SU's are suppose to act identical,...right?

Normally they would.  Note that if their idle screw settings are 
different then the first little bit of throttle you give it will 
affect one carb more than the other.  Also if the linkage isn't set 
to open them the same amount, one may open more than the other.  This 
is just a mechanical thing.  It isn't super sensitive but you do have 
to have them balanced mechanically before it makes sense to wonder 
why they don't seem to be behaving the same.

> Would there be any good likelyhood that thinner oil in one carb. might help
> sychronize their movements?

I wouldn't think so.


> One of my SU H6's dip stick's presses laterally on the piston's tube, so that
> it doesn't operate correctly.  Is this often corrected by simply bending the
> dip stick?
> This unequal rubbing proably won't affect idle, will it?


Shouldn't affect idle.  I wonder how the dipstick got bent!  You may 
be able to straighten it, but I wouldn't be surprised if it turns out 
to be hard to get right.

-- 
Jim Muller
jimmuller@rcn.com
'80 Spitfire, '70 GT6+



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