[Healeys] HS4 Tri-carb tuning

John Spaur jmsdarch at sbcglobal.net
Mon Jul 6 18:26:55 MDT 2020

I should have given a reference. It is from the S.U Burlen website, this
page, right hand side, last paragraph before the carb section image:

It does not flood the carb, it leans it out to the stall point. No, it is
not way out of normal, it is a test to determine if the carb mixture is

-----Original Message-----
From: rwil at sbcglobal.net [mailto:rwil at sbcglobal.net] 
Sent: Monday, July 6, 2020 4:38 PM
To: John Spaur <jmsdarch at sbcglobal.net>
Subject: Re: [Healeys] HS4 Tri-carb tuning

at least with the dual carb H4s lifting the pin only speeds or slows the
engine speed.  if it stalls the engine I have no idea what that means except
that something is way out of normal.

Maybe with tricarbs you set the throttle of the center carb at idle just a
bit opener than the other two or something special?  Sounds like the center
carb is the only one supplying fuel to the engine.
That way you could stall the engine by shutting it off.  but that isn't what
lifting the piston does - just adds more gas.  Maybe floods
it?   But the other two carbs are behaving as they should so nothing
makes much sense.


On Mon, 6 Jul 2020 15:39:20 -0700, you wrote:

>I installed three brand new HS4 carbs on my BT7 this weekend. They seem 
>to work really well with no load and light load on some very short test
>The jet adjusting nuts are very close to what the old ones were set to. 
>One of the tests is to lift the piston with the lifting pin as far as you
>That is supposed to stall the engine. However, this only works on the 
>center carb. When I test the front and rear, it just slows the engine down
a bit.
>What have others found when they do this test? BTW, I can hardly tell a 
>difference in the engine speed when I lift the pistons 1/32".
>San Jose, CA

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