[6pack] tr6 high idle continued - update

[Dave]

yesterday we did an interesting experiment.

we swapped carbs 1 (front) and 3 (rear, next to scuttle).  obviously we 
couldn't connect the linkages, but everything else hooks up.

after getting the car warmed up (had to manually push on two of the carbs 
accelerators to keep it going until then), I found that all three balanced 
very nicely and the car idled along happily at about 1100 to 1200 rpm (this 
car is rather modified so this is a good idle)

there was no more issue about one carb piston being higher or registering 
differently on my flow meter.  all were nicely in sync at this point.

putting the carbs back where they belonged the problem returned.  this 
problem was in evidence even with the accelerator linkage disconnected and 
the clips on the throttle linkages loose.  the rear carb pulls way more air 
than the other two, and the best I can do is about 2000 rpm idle





-----Original Message----- 
From: Ed McGuirk
Sent: Tuesday, February 05, 2013 9:41 PM
To: 6pack at autox.team.net
Subject: Re: [6pack] tr6 high idle continued

The lifted piston in the rear carb strongly suggests that all the extra
air is passing under that piston. You probably do not have a leak ( a
leak would not raise a carb piston), you probably have an out of sync
throttle plate or linkage. I think your next step should be to look
closely at the rearmost throttle plate. How it sits at idle and how it
moves with the other throttle plates and gas pedal. You probably will
not be able to lift the piston and see the throttle plate with the
engine running. You may need a flashlight and a mirror to see down the
carb throat.

ed

On 2/4/2013 2:00 PM, 6pack-request at autox.team.net wrote:
> Date: Sun, 3 Feb 2013 14:08:07 -0600
> From: "Dave" <dave at ranteer.com>
> To: "Triumph 6 Pack" <6pack at autox.team.net>
> Subject: [6pack] tr6 high idle continued
> Message-ID: <CA9F99F9AB1541E9A07E1E2D00EBBE34 at Datsun>
> Content-Type: text/plain; charset="us-ascii"
>
> update on tr6 idling high.   triple carb, mild cam, etc
>
> Here's what we did this morning:
>
> 1.  found what looked like a vacuum port in the bottom of the middle carb 
> and
> blocked it off.  it is likely once upon a time connected to the dizzy, 
> which
> no longer has a vacuum connection.
> 2.  blocked off all three vacuum ports on the top right of all three 
> carbs.
> these were connected to the valve cover, brake booster, and vapor recovery
> canister.
> 3.  the car started, and idled very nicely at around 1200.  but then as it
> warmed up, the idle increased back up to around 2500
> 4.  checked the position of the pistons in the 3 carbs.  the front and 
> center
> carb were more or less sitting at bottom, but the rear carb (by the 
> scuttle)
> the piston was noticeably raised.  blocking off that carb completely 
> killed
> the engine.  slowly blocking it off lowered the rpms, the more we blocked 
> it.