Subject: Re: [TR] SU H6 Carb Part Need

From: "Kinderlehrer" <[email-masked]>
Date: Mon, 17 Sep 2018 12:49:30 -0700

Did you try switching the domes and see if the problem follows the dome or
the piston? 
Bob

-----Original Message-----
From: Triumphs [mailto:[email-masked]] On Behalf Of Jim
Henningsen
Sent: Sunday, September 16, 2018 5:25 PM
To: 'Triumphs'
Subject: [TR] SU H6 Carb Part Need

Anyone have a spare SU H6 piston dome? Carbs on my 61 TR3A.  I believe I may
need another as the tolerance is too tight to get the piston to move up and
down easily and get the audible click. If you have one, please contact me
directly.
Thanks,
Jim Henningsen 

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From: Tony Drews <[email-masked]>
Date: Mon, 17 Sep 2018 20:10:21 -0500

Normally the dome and piston is a matched set.  Mixing them up can cause 
much havoc.

Tony

On 9/17/2018 2:49 PM, Kinderlehrer wrote:
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From: James Henningsen <[email-masked]>
Date: Tue, 18 Sep 2018 06:58:00 -0400

I had heard that also.   But also heard that over the years one can’t verify if the set is still the factory matched set.  John twist from university motors said a while back he never had a problem switching parts and checking tolerances.  I defer to the carb expert rebuilders out there. Jim

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> On Sep 17, 2018, at 9:10 PM, Tony Drews <[email-masked]> wrote:
> 
> Normally the dome and piston is a matched set.  Mixing them up can cause much havoc.
> 
> Tony
> 
> 
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From: "[email-masked]" <[email-masked]>
Date: Tue, 18 Sep 2018 10:22:03 -0500

I always either mark them, front & rear, or put them in separate bins while they are apart.  
Bill B
TS30800L

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On Sep 18, 2018, at 5:58 AM, James Henningsen <[email-masked]> wrote:

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From: "Randall" <[email-masked]>
Date: Tue, 18 Sep 2018 15:58:42 -0400

I don't have the link handy, but somewhere out there is a video, done by
John Twist IIRC, showing the "drop test".

Basically, you plug the holes in the bottom of the piston, push it to the
top of the dome, and then time how long it takes to fall out.  (Obviously
catching it as it does.)  There was a range of acceptable times (something
like 3 to 7 seconds, don't recall exactly); but the main point was that if
you have managed to mix them up between a pair of carbs, one will fall much
faster than the other.

Of course, too tight is rarely a problem unless the dome is damaged.  If
there is a tight spot, it can be identified with a little machinist's dye,
then rubbed out with very fine sandpaper.  The domes and pistons are very
soft, so go slowly and try the fit often.

I've never had to reduce the diameter of a piston; but it should be easy to
accomplish the same way.

-- Randall

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From: "Jim Henningsen" <[email-masked]>
Date: Tue, 18 Sep 2018 20:29:36 -0400

Thanks for everyone who has replied with help.  I polished the suction
chambers inside wall, piston exterior rings, and piston tube on each
assembly.  Used Wenol ultra soft metal polish.  Definitely helped remove
some of the friction that was occurring in the inner tube.  Next, I did the
piston balancing test from John Twist's You tube video.  I love his videos!
See below.

https://www.youtube.com/watch?v=IfU47Oqq9wA

Put masking tape on the piston air holes and tested piston drop time in
suction chambers.  One was 6 seconds and one 3 so not balanced.  I switched
pistons between same chambers and a magical 3 second drop on each piston.
They were pretty darn close to equal balance, maybe a quarter second off.  

No time to reassemble back on carb bodies to test on car tonight.  Hopefully
this solves the issue.  A little polishing to remove surface patina from
nearly 60 years and proper balancing the John Twist way.  Check out his 200
videos from University Motors.  Worth the watch.  Makes me wish I had an MG
when they were still open.  Did a Triumph guy just say that?  Blasphemy.
Thank you John Twist!
Cheers,
Jim Henningsen    

-----Original Message-----
From: Randall <[email-masked]> 
Sent: Tuesday, September 18, 2018 3:59 PM
To: 'James Henningsen' <[email-masked]>; 'Tony Drews'
<[email-masked]>
Cc: [email-masked]
Subject: RE: [TR] SU H6 Carb Part Need

-- Randall

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From: "Kinderlehrer" <[email-masked]>
Date: Wed, 19 Sep 2018 15:45:05 -0700

Perhaps they were already mixed up.

Bob

-----Original Message-----
From: Triumphs [mailto:[email-masked]] On Behalf Of Tony Drews
Sent: Monday, September 17, 2018 6:10 PM
To: [email-masked]
Subject: Re: [TR] SU H6 Carb Part Need

Tony

On 9/17/2018 2:49 PM, Kinderlehrer wrote:
> Did you try switching the domes and see if the problem follows the 
> dome or the piston?
> Bob
>
> From: Triumphs [mailto:[email-masked]] On Behalf Of 
> Jim Henningsen
> Anyone have a spare SU H6 piston dome? Carbs on my 61 TR3A.  I believe 
> I may need another as the tolerance is too tight to get the piston to 
> move up and down easily and get the audible click. If you have one, 
> please contact me directly.
> Thanks,
> Jim Henningsen
>
> http://autox.team.net/mailman/options/triumphs/[email-masked]
>