[TR] 61 TR3A SU H6 Carb Issues

Tue Oct 16 10:58:28 MDT 2018

 First off, let me say that if you don't have a flow meter, using the hose/listening method works well enough for our primitive engines.  But the meter will provide greater accuracy.  Sure putting the airflow meter effects the flow through the carb (a bit) but we are not trying to get an absolute calibration.  We want a relative calibration and if both carbs behave the same with the flow meter in place they are set the same.  And that is the end result desired.

Dave Massey

-----Original Message-----
From: ptegler <ptegler at verizon.net>
To: dave1massey <dave1massey at cs.com>; trguy75 <trguy75 at gmail.com>; triumphs <triumphs at autox.team.net>
Sent: Tue, Oct 16, 2018 11:27 am
Subject: Re: [TR] 61 TR3A SU H6 Carb Issues

agreed.... especially considering that no one stated the human ear was 'better' than an instrument. BUT.....
Take a look at any procedure for multiple carbs (greater than two)   EG: quads on a bike or 8/12 carbs on a Ferrari. ...even three DCOEs on a Triumph 6
NONE suggest a flow meter blocking the intake.  On most bike engines you use multiple water columns via taps on the sides of the carbs specifically designed to facilitate balancing. Compared to most LBC's none have a balance port in the intake manifold so no 'cross contamination ' from air flow via another carb. Block one of four bike carbs and the engine will slow very noticeably.

sure the 'premise' is you block both carbs (one at a time) but neither is 'as is' when running. When you place the meter over the carb throat you change the depression and running position of the piston in the throat.  Air volume vs velocity is changed...effecting the carb operations, both air AND fuel.  when you slow down the air velocity it doesn't pull as much fuel, and starts consuming air from the other carb via the balance port in the manifold etc etc.  

You need to use whatever method best suites your sensibilities. As too the repercussions of you procedures. Each case is different, each case has different expediencies, habits and results   :-)

ptegler

-----Original Message-----
From: DAVID MASSEY <dave1massey at cs.com>
To: ptegler <ptegler at verizon.net>; trguy75 <trguy75 at gmail.com>; triumphs <triumphs at autox.team.net>
Sent: Tue, Oct 16, 2018 7:34 am
Subject: Re: [TR] 61 TR3A SU H6 Carb Issues

Seriously though.... what method didyou use to balance the air      flow at idle? One of those little flow meters?
      NOPE NADA STOP right there.   Think about it...you're sealing off      the air to get the bubble to rise so of course the idle      changes....so the balance tube in the manifold sucks from the      other carb, bypassing the fuel pull.

 What are you talking about?  Sure you affect airflow with the airflow meter but you are affecting both carbs equally when you switch from carb to carb.  If you get the same reading from both they are being effected the same and have the same starting point.  The concept that the human ear is better than an instrument specifically designed to measure airflow is pure hubris.

One thing to watch out for is assuming that since the carbs are balanced at idle they are balanced under throttle.  Be very careful when tightening down the linkage to ensure that both carbs open simultaneously.  This is particularly important on the TR6-style linkage that has built-in disengagement zones.

Dave Massey

-----Original Message-----
From: Paul Tegler <ptegler at verizon.net>
To: Jim Henningsen <trguy75 at gmail.com>; triumphs <triumphs at autox.team.net>
Sent: Tue, Oct 16, 2018 3:16 am
Subject: Re: [TR] 61 TR3A SU H6 Carb Issues

ok....what do you mean by 'carbs aren't running smoothly'  ?

Engine is not smooth?.. sputtering?  not running smooth while      cruising?

An old adage.... (well two actually)
      "..most carb problems are electrical..."  and "..most ignition      problems are the carbs"

Seriously though.... what method didyou use to balance the air      flow at idle? One of those little flow meters?
      NOPE NADA STOP right there.   Think about it...you're sealing off      the air to get the bubble to rise so of course the idle      changes....so the balance tube in the manifold sucks from the      other carb, bypassing the fuel pull.

I was finally convinced by an old mechanic and have learned from      tuning more SU and ZS carbs than I care to mention.... use a 1/4"      fuel line as a stethoscope ...one end in your ear..the other just      up against the edge (not in) the carb throat. blocks minimal      air... and believe me you can hear as little 1-2 cfm readily, but      you can also hear the gurgle of the fuel flow!   Years ago I      actually gave away my flow gauges.

Eons ago..I got so fed up once I bought brand new NOS SU carbs to      replace mine after three rebuilds of the orig units. BUT...STILL      had the same issue...smooth speed cruising and it ran like crap.      Pull the choke out and it ran fine, but had to push it in at      closed or low speed throttle. Spent a year+ and hundreds of      messages on various LBC lists....still to no avail.  Than one day      at a car show.... I saw a guy with an identical setup.... open big      round K&Ns and a end plate but had his air filters nearly 3/4      closed off with duct tape.  In the end, the problem was incorrect      vacuum effects ...not enough air velocity when the piston was      mid/down as there was no restriction from the air filters.

hhmmm.... ok...
      http://www.teglerizer.com/mgstuff/a_stumble_at_cruise.htm

ptegler

On 10/15/2018 7:40 PM, Jim Henningsen      wrote:

Ok, I thought I had this rebuild all nailed down.  Finally got around to
getting carbs balanced and set for correct mixture.  After new kits, testing
piston drop timing per John Twist you tube clip (great clip), and spending
two hours fine tuning air flow and mixture.  The carbs aren't running
smoothly.  There is something not right and I am throwing in the towel.
Don't have a reliable mechanic that I trust for this in Ocala.  Any
recommendations on a rebuilder to send these two to have them checked
professionally.  

Joe Curto?
Jeff Payla at Paltech - cant seem to get a response from him.
Buy new (ouch)
Others?  

Thanks in advance
Jim Henningsen
Ocala FL
61 TR3A  eager to enjoy driving it in fall in Florida
62 TR4 eager to have restoration finished
75 TR6 eager to have new race motor put in
82 Jeep ld reliable - get in and go
2002 Triumph Trophy 1200 eager to just get out and be used.

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-- 
Paul Tegler
ptegler at verizon.net  www.teglerizer.com

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