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 <tr3driver@ca.rr.com>
Sent: Tuesday, September 18, 2018 3:59 PM
To: 'James Henningsen' <trguy75@gmail.com>; 'Tony Drews'
<tony@tonydrews.com>
Cc: triumphs@autox.team.net
Subject: RE: [TR] SU H6 Carb Part Need
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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